Tribological Behavior of Soybean Oil

Constantin Georgescu, Lorena Deleanu and George Catalin Cristea

## Abstract

This chapter presents experimental data in the favor of using soybean oil, additivated or not, as lubricants, the market share of the soybean oil on the lubricants' market, a SWOT analysis for better configuring the tribological characteristics of the soybean oil and tribological parameters as friction coefficient, wear scar diameter, wear rate of wear scar diameter, etc. and their dependence on testing regime (load and speed). Also, the influence of temperature, shear rate, and oxidation parameters on the soybean oil viscosity is discussed.

Keywords: soybean oil, viscosity, tribology, friction, wear, scar wear diameter

## 1. About soybean oil, in the favor of using it as lubricant

## 1.1 SWOT and market analysis

The world vegetal oil production was around 182 million tons in 2016/2017 [1]. In 2017, the bio-lubricants market was evaluated at 2.47 billion USD, and it would value 3.36 billion USD by 2022, at a growth rate of 6.4%.

Environmental regulations, increasing production of vegetal oils, and their applications are market drivers. But their still high price and the decline in petrol resources are factors hindering the growth of this particular market [2]. North America is intended to be the largest market by 2022, but Europe led bio-lubricants market in 2016 and some of its member states (Germany, France, and Finland, but also Norway as an economic partner) ask for environment protection and biodegradability standards and regulations in the favor of these lubricants. For instance, the focus on "green chemistry", the regulation on environment protection and advances in research, should lead the bio lubricants to develop and gain the market on longer term, as an increase of using them is estimated if a more strong incentive policy is applied in European Union (Table 1).

The major restraints are deficiency in interconnecting regulations and higher prices than petroleum-based lubricants. The North American market for soy-based lubricants was estimated at USD 191.5 million in 2016 [4].

The Ag-Based Industrial Lubricants Research Center (USA, Northern Iowa) patented 30 genetically modified soybean lubricants (oils and greases) for tractor, chains, compressor, manufacturing processes and transmissions, metalworking and cooling fluids, fluids for the food industry, oils, transformer oils, greases for cars, railways, etc. [5].

**68**

*Soybean - Biomass, Yield and Productivity*

[18] VSN Internatiomal. Gensta® 18th Edition PC/Windows XP.Copyright 2015. VSN International Ltd; 2015. https://www.vsni.co.uk/software/ genstat[Accessed: 20/08/2018]

root growth under water stress. Journal of Experimental Botany. 2002;**53**:33-37

[26] Tseng IC, Hong CY, Yu SM, Ho TTD. Abscisic acid- and stress-induced highly proline-rich glycoproteins regulate root growth in rice. Plant Physiology. 2013;**163**:118-134

[17] Rowse HR, Phillips DA. An instrument for estimating the total length of root in sample. Journal of Applied Ecology. 1974;**11**:309-314

[19] Manavalan LP, Guttikonda SK, Nguyen VT, Shannon JG, Nguyen HT. Evaluation of diverse soybean germplasm for root growth and architecture. Plant and Soil.

[20] Beebe SE, Rao IM, Blair MW, Acosta-Gallegos JA. Phenotyping common beans for adaptation to drought. Frontiers in Physiology. 2013;**4**:1-20. DOI: 10.3389/

[21] Okogbenin E, Setter TL, Ferguson M, Mutegi R, Ceballos H, Olasanmi B, et al. Phenotypic approaches to

drought in cassava: Review. Frontiers in

[22] Creelman RA, Mason HS, Bensen RJ, Boyer JS, Mullet JE. Water deficit and abscisic acid cause differential inhibition of shoot versus root growth in soybean seedlings. Plant Physiology.

[23] Hsiao TC, Xu LK. Sensitivity of growth of roots versus leaves to water stress: Biophysical analysis and relation to water transport. Journal of Experimental Botany.

[24] Bloom AJ, Chapin FS, Mooney HA. Resource limitation in plants—An economic analogy. Annual Review of Ecology and Systematics.

[25] Sharp RE, LeNoble ME. ABA, ethylene and the control of shoot and

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fphys.2013.00035

Physiology. 2013;**4**:1-15

1990;**92**:205-214

2000;**51**:1595-1616

1985;**16**:363-392


\*Lubricants for gears, engine, metal working, electric transformers, and base-stock for greases.

#### Table 1.

Estimation of consumption of biolubricants [3].

#### Figure 1.

Soybean lubricant market in the USA, depending on the application, for the time interval 2014–2025 (in million USD) [4].

A study of the American market reveals that the value of lubricants based on soybean oil will constantly increase, almost similar for major applications of these lubricants (engines, food processing, manufacturing process, and hydraulics) (Figure 1).

Research on soybean oil as gear lubricant was published by Ibrahim [6]. Soybean oil is used as biodiesel in a small share as compared to other vegetal oils, especially rapeseed oil, but the tribological characteristics are important even in this application [7].

with soil nature, climate, and human intervention on seeds, and even for the same place and the same type of seed, the annual conditions may influence the quality of

ysis [14], for introducing vegetal oils in environmentally sensitive industries, agriculture, and transport, including soybean oil, as lubricants, underlines that a set of properties should be considered when the designer decides this lubrication

• a better lubricity, low volatility and a high viscosity index [17],

chemically modified or additivated, are discussed:

Vegetal oils and their composition in fat acids [12].

Strengths, weaknesses, opportunities, and threats, well known as a SWOT anal-

Strengths in the favor of using soybean oil as oil for lubrication, either as neat,

vegetal oil.

71

Figure 3.

Figure 2.

Consumption of vegetal oils (adapted from [11]).

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

solution [15–17].

• biodegradability [18],

Energy resources from renewable crops have gained prominence in order to replace petroleum products. Bio-lubricants become acceptable alternatives to conventional lubricants. Despite their benefits, these are still far from being practical. Since bio-lubricants are produced from raw vegetal oils, they have poor flow properties at low temperature and poor thermo-oxidative and hydrolytic stability. However, these shortcomings can be addressed by modifying the vegetal oils chemically [8] or incorporating additives into the oils [9, 10]. From Figure 2, one may notice that the production of soybean oil has been increasing constantly, and a considerable amount is used for producing lubricants.

Figure 3 presents the diversity in composition in fatty acids of several vegetal oils [12]. This would be the explanation of the very particular behavior of vegetal oils under boundary or fluid lubrication. Hence, it is necessary to control the fatty acid composition of vegetal oils [13]. The composition in fatty acids could also vary

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

#### Figure 2.

Consumption of vegetal oils (adapted from [11]).

#### Figure 3.

A study of the American market reveals that the value of lubricants based on soybean oil will constantly increase, almost similar for major applications of these lubricants (engines, food processing, manufacturing process, and hydraulics)

Research on soybean oil as gear lubricant was published by Ibrahim [6]. Soybean oil is used as biodiesel in a small share as compared to other vegetal oils, especially rapeseed oil, but the tribological characteristics are important even in

Soybean lubricant market in the USA, depending on the application, for the time interval 2014–2025 (in

2008 Production forecast 2020

Biolubricants, if a moderate incentive policy will act [t]

650,000 68,000 155,000 230,000

50,000 29,000 37,000 40,000

100,000 9000 15,000 30,000

Other uses\* 3,600,000 31,000 70,000 120,000 Total 4,400,000 137,000 277,000 420,000

\*Lubricants for gears, engine, metal working, electric transformers, and base-stock for greases.

Biolubricants, if a strong incentive policy is applied [t]

Biolubricants [t]

Energy resources from renewable crops have gained prominence in order to replace petroleum products. Bio-lubricants become acceptable alternatives to conventional lubricants. Despite their benefits, these are still far from being practical. Since bio-lubricants are produced from raw vegetal oils, they have poor flow properties at low temperature and poor thermo-oxidative and hydrolytic stability. However, these shortcomings can be addressed by modifying the vegetal oils chemically [8] or incorporating additives into the oils [9, 10]. From Figure 2, one may notice that the production of soybean oil has been increasing constantly, and a consider-

Figure 3 presents the diversity in composition in fatty acids of several vegetal oils [12]. This would be the explanation of the very particular behavior of vegetal oils under boundary or fluid lubrication. Hence, it is necessary to control the fatty acid composition of vegetal oils [13]. The composition in fatty acids could also vary

(Figure 1).

70

Figure 1.

million USD) [4].

Industrial applications

Hydraulic fluids

Oils for chainsaws

Table 1.

Mold release oils

Lubricants [t]

Soybean - Biomass, Yield and Productivity

Estimation of consumption of biolubricants [3].

this application [7].

able amount is used for producing lubricants.

Vegetal oils and their composition in fat acids [12].

with soil nature, climate, and human intervention on seeds, and even for the same place and the same type of seed, the annual conditions may influence the quality of vegetal oil.

Strengths, weaknesses, opportunities, and threats, well known as a SWOT analysis [14], for introducing vegetal oils in environmentally sensitive industries, agriculture, and transport, including soybean oil, as lubricants, underlines that a set of properties should be considered when the designer decides this lubrication solution [15–17].

Strengths in the favor of using soybean oil as oil for lubrication, either as neat, chemically modified or additivated, are discussed:


• better flammability characteristics (auto ignition points and higher ignition temperature on hot surfaces) than many mineral oils and similar to those of the rapeseed oil [19, 20],

Solea [19] did a comparative study for evaluating the viscosity of four vegetal oils, including soybean oil, experimental data proving the dependence of viscosity on temperature and shear rate (Figure 4), and tests done with the help of a rotational viscometer Rheotest2. The mineral oil OMV VG 46 was tested for comparison reason. In the temperature range 30–60°C, a more accentuated decrease of dynamic viscosity is noticed as compared to that characterizing the range 60–90°C. On the entire range of tested shear rates, the lowest decrease of viscosity was obtained for the corn oil (75.81%) and for the soybean oil (76.25%). For all tested vegetal oils, the dynamic viscosity decrease was 75–80%. This "agglomeration" of data may be the results of similar composition in fatty acids (see Table 2). The dynamic viscosity of oils also decreases when temperature increases, for different shear rates (Figure 5), and for the lubricants tested in [19], the values have the tendency to agglomerate in the narrow range at higher temperatures (60–90°C) and for higher shear rates (Figure 5). This behavior has been also noticed in [38, 39].

Viscosity as a function of temperature for four vegetal oils and a hydraulic mineral oil for comparison reason

Fatty acid Symbol Olive oil Soybean oil Corn oil Rapeseed oil Myristic acid C14:0 — 0.11 0.05 0.05 Palmitic acid C16:0 12.6 12.7 12.4 4.84 Palmitoleic acid C16:1 1.20 0.13 — 0.06 Heptadecanoic acid C17:0 0.10 0.05 0.12 0.14 Heptadecenoic acid C17:1 0.10 0.06 0.05 — Stearic acid C18:0 — 5.40 2.10 0.14 Oleic acid C18:1 79.30 21.60 28.45 62.73 Linoleic acid C18:2 4.70 52.40 54.10 22.4 Linolenic acid C18:3 0.80 5.70 1.10 7.50 Arachidic acid C20:0 0.40 0.25 0.40 0.50 Eicosenoic acid C20:1 0.25 0.20 0.35 1.25 Behenic acid C22:0 — 0.50 0.10 0.30 Erucic acid C22:1 — 0.16 — — Lignoceric acid C24:0 0.16 0.20 0.10 —

. (b) Shear rate 80 s<sup>1</sup>

.

(OMV ISO VG46), at two shear rate [19]. (a) Shear rate 10 s<sup>1</sup>

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 4.

Table 2.

73

Fatty acid composition of the tested oils [19].


Weak points for this vegetal oil include:


The user should expect this vegetal oil to change its viscosity, oxidation stability, and polymerization during exploitation in a more intense way than mineral and synthetic lubricants. Chemical modification of soybean oil and/or the use of antioxidants [23, 34–36] could positively influence, but these will increase the cost of lubricant.

Opportunities are related to complying with more stringent environmental protection requirements that will minimize health and pollution risks. The new market shares for organic and biodegradable lubricants (obtained from renewable resources, especially plants) have increased for areas such as hydraulic fluids, chain lubricants, mold lubricants, two-stroke engines, turbine fluids, etc. [21].

Threats are the following:


## 1.2 Viscosity of soybean oil and soybean oil-based lubricants

For a lubricant to exhibit a better tribological behavior, it has to have an appropriate viscosity that will not decrease excessively when the working temperature increases. For many vegetal oils, their viscosity is low even at room temperature and it decreases dramatically when the oil is heated [19, 23, 26, 37].

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

Solea [19] did a comparative study for evaluating the viscosity of four vegetal oils, including soybean oil, experimental data proving the dependence of viscosity on temperature and shear rate (Figure 4), and tests done with the help of a rotational viscometer Rheotest2. The mineral oil OMV VG 46 was tested for comparison reason. In the temperature range 30–60°C, a more accentuated decrease of dynamic viscosity is noticed as compared to that characterizing the range 60–90°C. On the entire range of tested shear rates, the lowest decrease of viscosity was obtained for the corn oil (75.81%) and for the soybean oil (76.25%). For all tested vegetal oils, the dynamic viscosity decrease was 75–80%. This "agglomeration" of data may be the results of similar composition in fatty acids (see Table 2).

The dynamic viscosity of oils also decreases when temperature increases, for different shear rates (Figure 5), and for the lubricants tested in [19], the values have the tendency to agglomerate in the narrow range at higher temperatures (60–90°C) and for higher shear rates (Figure 5). This behavior has been also noticed in [38, 39].

#### Figure 4.

• better flammability characteristics (auto ignition points and higher ignition temperature on hot surfaces) than many mineral oils and similar to those of the

• a good solubility for contaminants, additives, and polar deposits as compared

• extraction from renewable resources (even with a reference to 100 years) or

• environmental (nonpolluting or environmentally friendly) [21–23],

• lower viscosity as compared to mineral and synthetic oils [25–28],

• temperature range lower than that of mineral and synthetic oils [32],

• poorer properties at low temperature as compared to other lubricants

The user should expect this vegetal oil to change its viscosity, oxidation stability, and polymerization during exploitation in a more intense way than mineral and synthetic lubricants. Chemical modification of soybean oil and/or the use of antioxidants [23, 34–36] could positively influence, but these will increase the cost of

Opportunities are related to complying with more stringent environmental protection requirements that will minimize health and pollution risks. The new market shares for organic and biodegradable lubricants (obtained from renewable resources, especially plants) have increased for areas such as

hydraulic fluids, chain lubricants, mold lubricants, two-stroke engines, turbine

• the need to redesign systems using bioliquids, a possibly costlier solution,

• accepting lowering some system operating parameters (especially load and

• the price still high (but not forgetting that, for example, synthetic oils in the 1990s were almost 10 times more expensive than mineral ones, today the ratio being only 3 to 1), market and users' inertia, the diversity of environmental and safety specifications, and a global policy that has not yet been clearly

For a lubricant to exhibit a better tribological behavior, it has to have an appropriate viscosity that will not decrease excessively when the working temperature increases. For many vegetal oils, their viscosity is low even at room temperature and

the possibility of recycling or re-use of the lubricant [24].

rapeseed oil [19, 20],

Soybean - Biomass, Yield and Productivity

to mineral oils [16, 17],

Weak points for this vegetal oil include:

• oxidation stability [9, 16, 19, 29–31],

[27, 29, 33].

lubricant.

72

fluids, etc. [21].

Threats are the following:

maintenance, but not limited to) [22],

addressed on environmental issues.

1.2 Viscosity of soybean oil and soybean oil-based lubricants

it decreases dramatically when the oil is heated [19, 23, 26, 37].

Viscosity as a function of temperature for four vegetal oils and a hydraulic mineral oil for comparison reason (OMV ISO VG46), at two shear rate [19]. (a) Shear rate 10 s<sup>1</sup> . (b) Shear rate 80 s<sup>1</sup> .


#### Table 2.

Fatty acid composition of the tested oils [19].

(Figure 6), but also at 90°C (Figure 7), with more than 300%, making the oxidized oil not to be recommended in applications where this oil has a working temperature

A similar tendency of evolution for soybean viscosity with shear rate and temperature obtained Esteban [40] and Cristea [41] but the latter for higher shear rates,

In terms of temperature viscosity dependence, the nanoadditives based on car-

temperatures: (a) Oxidation at constant temperature 110°C. (b) Oxidation at constant temperature 120°C

Dynamic viscosity of soybean oil, nonadditivated, and additivated with 1% wt nanoadditive (tests done at

, non-oxidized and oxidized at different

more than 110°C and the oxidation could be generated (splash lubrication). Figure 8 presents the influence of temperature on the dynamic viscosity of soybean oil when it is measured after oxidation during 5 and 10 hours, respectively,

using a Brookfield CAP 2000+ viscometer with cone 8 (Figure 9).

bon (black carbon, graphite, and graphene) are separated in two groups:

at constant temperatures of 110 and 120°C.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

Variation of dynamic viscosity of soybean oil, at shear rate of 80 s<sup>1</sup>

Figure 8.

Figure 9.

75

shear rate 1000 s<sup>1</sup>

) [41].

[19].

Figure 5.

Dynamic viscosity of soybean oil and a hydraulic mineral oil OMV ISO VG46, for different shear rates [19].

The temperature increase intensifies the intermolecular movement and reduces the attraction among oil molecules.

Solea [19] also measured the viscosity of soybean oil after oxidation, and data reveal a weak point of this vegetal oil: the oxidized soybean oil has an increasing viscosity with the time it bears oxidation (Figures 6 and 7). The forced oxidation is realized by circulating air in the oil with a stable temperature.

Only a difference of 10°C of oil in the oxidation test (from 110 to 120°C) for tests during 10 hour modifies the dynamic viscosity of soybean oil, measured at 30°C

#### Figure 6.

Dynamic viscosity of soybean oil at 30°C, as a function of shear rate and oxidation time, after oxidation [14]. (a) After oxidation at temperature of 110°C. (b) After oxidation at temperature of 120°C.

#### Figure 7.

Dynamic viscosity of soybean oil at 90°C as a function of shear rate and oxidation time (air flow 20 l/h in 25 ml of oil) [19]. (a) After oxidation at temperature of 110°C. (b) After oxidation at temperature of 120°C.

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

(Figure 6), but also at 90°C (Figure 7), with more than 300%, making the oxidized oil not to be recommended in applications where this oil has a working temperature more than 110°C and the oxidation could be generated (splash lubrication).

Figure 8 presents the influence of temperature on the dynamic viscosity of soybean oil when it is measured after oxidation during 5 and 10 hours, respectively, at constant temperatures of 110 and 120°C.

A similar tendency of evolution for soybean viscosity with shear rate and temperature obtained Esteban [40] and Cristea [41] but the latter for higher shear rates, using a Brookfield CAP 2000+ viscometer with cone 8 (Figure 9).

In terms of temperature viscosity dependence, the nanoadditives based on carbon (black carbon, graphite, and graphene) are separated in two groups:

#### Figure 8.

The temperature increase intensifies the intermolecular movement and reduces the

Dynamic viscosity of soybean oil and a hydraulic mineral oil OMV ISO VG46, for different shear rates [19].

realized by circulating air in the oil with a stable temperature.

Solea [19] also measured the viscosity of soybean oil after oxidation, and data reveal a weak point of this vegetal oil: the oxidized soybean oil has an increasing viscosity with the time it bears oxidation (Figures 6 and 7). The forced oxidation is

Only a difference of 10°C of oil in the oxidation test (from 110 to 120°C) for tests during 10 hour modifies the dynamic viscosity of soybean oil, measured at 30°C

Dynamic viscosity of soybean oil at 30°C, as a function of shear rate and oxidation time, after oxidation [14].

Dynamic viscosity of soybean oil at 90°C as a function of shear rate and oxidation time (air flow 20 l/h in 25 ml of oil) [19]. (a) After oxidation at temperature of 110°C. (b) After oxidation at temperature of 120°C.

(a) After oxidation at temperature of 110°C. (b) After oxidation at temperature of 120°C.

attraction among oil molecules.

Soybean - Biomass, Yield and Productivity

Figure 5.

Figure 6.

Figure 7.

74

Variation of dynamic viscosity of soybean oil, at shear rate of 80 s<sup>1</sup> , non-oxidized and oxidized at different temperatures: (a) Oxidation at constant temperature 110°C. (b) Oxidation at constant temperature 120°C [19].

#### Figure 9.

Dynamic viscosity of soybean oil, nonadditivated, and additivated with 1% wt nanoadditive (tests done at shear rate 1000 s<sup>1</sup> ) [41].


For any tested temperature and shear rate, the dynamic viscosity of soybean oil may be ordered [19]:

animal fats have such molecular structures, and therefore, they have good results in

Solid lubricants are added to vegetal oils with the same purpose of reducing friction and wear. This group includes not only carbon materials (fullerene, nanotubes, graphite, graphene, etc.) but also molybdenum and wolfram sulfides and fluorinated polymers, such as polytetrafluorethylene (PTFE) and perfluoropolyalkylethers (PFPAE). These can also be added in greases and composites that will function in dry conditions [46]. Solid lubricants (micro or nano) also help in situations where sliding surfaces have a rougher texture, "leveling" the profile of both surfaces. They are also recommended for reciprocal movements (in the case of the piston ring), which also produces a reduction in wear. They are added to lubricants that come into contact with surfaces with which EP (extreme pressure) additives cannot chemically react, such as polymers and ceramics and some of their

Friction modifying and wear reducing additives can be grouped into solid lubricants and organic modifiers. The first group consists of carbon materials (graphite, graphene, black carbon, and fullerene), lamellar sulfides (tungsten and molybdenum), metal salts (boron nitride), and metal oxides (CuO, ZnO, and TiO2 [47], which is not mentioned in [23]) but also linear polymers (polytetrafluoroethylene) [48]. Among the organic additives that act as friction modifiers are carboxylic acids or derivatives (stearic acid and esters), amides, imides, amines and their derivatives (oleyl amide, etc.), phosphoric and phosphonic acid derivatives, and organic polymers (methacrylates) [42, 43]. Regeneration of the friction reducing layer depends on additive concentration and conditions in which the tribosystem operates (speed,

Literature reported relatively low results on nanofluids as lubricants, mostly on transformer oil, silicon oil, gear oil, and heat transfer oil [49]. Limited investigations on the influence of nanoadditives on vegetal oils are presented [12]. Even if modern equipment working under high load, speed, and thermal conditions requires cooling and efficient lubrication, and for this concept, mineral and synthetic oils are still preferred and investigations on vegetal oils are needed for particular applications with environmental impact and in the perspective of oil resources extinction [50].

Wu et al. [43] propose a model that considers the lubricating additive concentration (see Figure 10). Although the model was created after experiments with TiO2 as additive, it can be used to explain the behavior of lubricants with other nanoscale particles (metal 40 oxides, carbon materials, etc.). The fluid lubrication mechanism with nanoadditives has been also described in the works [52–54].

The mechanism for reducing friction and antiwear mechanism of nanoparticles in lubricants has been investigated, and it is based on the following processes [43]:

The first two mechanisms have a direct effect on lubrication [61]. In the case of rolling, no chemical reactions occur, and spherical or oval nanoparticles are willing

reducing friction.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

composites [42].

load, temperature, and contamination) [42].

• micro-roll process [51, 55],

77

• smoothing/leveling process [60],

• polishing process [51, 61], (Figure 10).

• process of forming a protective film [56–59],

2.2 Specific processes for lubrication with nanoadditives

ηsoybean oil < η5 hour oxidation soybean oil < η10 hour oxidation soybean oil

The increase in dynamic viscosity could be a criterion when evaluating the oxidation of vegetal oil. The soybean oil in modern applications especially needs a high degree of chemical stability of the lubricant.

## 2. Additivation of soybean oil

## 2.1 Classification of additives

Based on several relevant works in the literature [12, 42–45], the authors propose the classification given in Table 3.

Friction modifiers are adsorbed or fixed to the surface and form a film or a powdery intermediate layer that reduces friction. They can be classified into two distinct groups depending on the friction reduction mechanism:


The first is generally due to polar molecules having a polar functional radical (alcohols, aldehydes, ketones, esters, and carboxylic acids) and a nonpolar terminal group. The polar group of the molecule adheres to the surface with long chains exposed to moving surfaces, reducing friction. They may also have polar elements that can chemically react with the surface to form a protective film. Vegetal oils and


## Table 3.

A classification of additive for lubricants.

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

• black carbon does not significantly affect this dependence,

viscosity dependence on temperature.

Soybean - Biomass, Yield and Productivity

high degree of chemical stability of the lubricant.

2. Additivation of soybean oil

pose the classification given in Table 3.

• through the adsorbed film,

Additives for lubricants

Modifiers of chemical properties

Deposit control additives

Antioxidation additives

Biodegradability

Table 3.

76

• by friction with the third body.

Modifiers of physical properties

Viscosity control additives

Poor point depressants

additives

Detergents Antifoaming

Toxicity Dispersants

A classification of additive for lubricants.

2.1 Classification of additives

may be ordered [19]:

• nanographite and nanographene move down the curves of the dynamic

For any tested temperature and shear rate, the dynamic viscosity of soybean oil

ηsoybean oil < η5 hour oxidation soybean oil < η10 hour oxidation soybean oil

The increase in dynamic viscosity could be a criterion when evaluating the oxidation of vegetal oil. The soybean oil in modern applications especially needs a

Based on several relevant works in the literature [12, 42–45], the authors pro-

Friction modifiers are adsorbed or fixed to the surface and form a film or a powdery intermediate layer that reduces friction. They can be classified into two

The first is generally due to polar molecules having a polar functional radical (alcohols, aldehydes, ketones, esters, and carboxylic acids) and a nonpolar terminal group. The polar group of the molecule adheres to the surface with long chains exposed to moving surfaces, reducing friction. They may also have polar elements that can chemically react with the surface to form a protective film. Vegetal oils and

Improvers of tribological behavior

Inorganic Phosphorus additives, like

package

Extreme pressure additives

dialkyldithiophosphate (ZDDP), sulfur additives, sulfur–phosphorus additives, phosphorus–nitrogen additives, nitrogen additives, halogen additives, mixt additive

Antiwear and friction modifiers

Organic

distinct groups depending on the friction reduction mechanism:

animal fats have such molecular structures, and therefore, they have good results in reducing friction.

Solid lubricants are added to vegetal oils with the same purpose of reducing friction and wear. This group includes not only carbon materials (fullerene, nanotubes, graphite, graphene, etc.) but also molybdenum and wolfram sulfides and fluorinated polymers, such as polytetrafluorethylene (PTFE) and perfluoropolyalkylethers (PFPAE). These can also be added in greases and composites that will function in dry conditions [46]. Solid lubricants (micro or nano) also help in situations where sliding surfaces have a rougher texture, "leveling" the profile of both surfaces. They are also recommended for reciprocal movements (in the case of the piston ring), which also produces a reduction in wear. They are added to lubricants that come into contact with surfaces with which EP (extreme pressure) additives cannot chemically react, such as polymers and ceramics and some of their composites [42].

Friction modifying and wear reducing additives can be grouped into solid lubricants and organic modifiers. The first group consists of carbon materials (graphite, graphene, black carbon, and fullerene), lamellar sulfides (tungsten and molybdenum), metal salts (boron nitride), and metal oxides (CuO, ZnO, and TiO2 [47], which is not mentioned in [23]) but also linear polymers (polytetrafluoroethylene) [48]. Among the organic additives that act as friction modifiers are carboxylic acids or derivatives (stearic acid and esters), amides, imides, amines and their derivatives (oleyl amide, etc.), phosphoric and phosphonic acid derivatives, and organic polymers (methacrylates) [42, 43]. Regeneration of the friction reducing layer depends on additive concentration and conditions in which the tribosystem operates (speed, load, temperature, and contamination) [42].

Literature reported relatively low results on nanofluids as lubricants, mostly on transformer oil, silicon oil, gear oil, and heat transfer oil [49]. Limited investigations on the influence of nanoadditives on vegetal oils are presented [12]. Even if modern equipment working under high load, speed, and thermal conditions requires cooling and efficient lubrication, and for this concept, mineral and synthetic oils are still preferred and investigations on vegetal oils are needed for particular applications with environmental impact and in the perspective of oil resources extinction [50].

### 2.2 Specific processes for lubrication with nanoadditives

Wu et al. [43] propose a model that considers the lubricating additive concentration (see Figure 10). Although the model was created after experiments with TiO2 as additive, it can be used to explain the behavior of lubricants with other nanoscale particles (metal 40 oxides, carbon materials, etc.). The fluid lubrication mechanism with nanoadditives has been also described in the works [52–54].

The mechanism for reducing friction and antiwear mechanism of nanoparticles in lubricants has been investigated, and it is based on the following processes [43]:


The first two mechanisms have a direct effect on lubrication [61]. In the case of rolling, no chemical reactions occur, and spherical or oval nanoparticles are willing

Figure 10.

The lubricating mechanism of water-based lubricants and TiO2 as an additive. (a) rolling effect, (b) mending effect, (c) polishing effect, and (d) effect of protective film [51].

to roll. The lubrication mechanism of nanoparticles as friction modifiers includes three types of friction [62]:


A study by Lahouij et al. in 2012 [65] shows how the WS2 (wolfram disulfide) particle protects the direct contact between metal asperities (Figure 13). The ovoid structure functions as a shock absorber and either the structure collapsed, or the particle was fragmented, it continued to remain between the two solid bodies. The hollow core of the particle was visible, and the deformation was large at the beginning of the stress, but as the load increased, the particle behaved like a variableelasticity spring, the elastic characteristic actually increasing. Then, the particle begins to tear or scissor, and, finally, the WS2 particle exfoliated in fragments.

Photos taken from the work of Lahouij et al. [65], the steps (here only two) through which a particle of WS2

The effect of relative size of surface texture and additive particles: particle with similar dimensions as the profile

From the studied literature, there is a tendency for deep research on additives in vegetal oils, especially those intended for lubrication. Attention should be focused

3. Tribological characterization of lubricants based on soybean oil

3.1 Tribological parameters and testing equipment related to lubricants

In order to assess the quality of lubricants, it is important to establish the test methodology (equipment, parameters, and investigations during and after testing). Their selection depends primarily on the practical use for which the lubricant is tested, and the selected tribotester should approach as much as possible to the

Tribological tests can be grouped in severe tests and tests under normal working conditions. The here-presented results could be appreciated as moderate regimes. Depending on the future application and the researchers' abilities and knowledge, tribological characterization will be done by a set of parameters, one being insufficient for this purpose. The evaluation of the results is often done by accepting a compromise, as durability and reliability of a system are influenced by synergic effects of actual dynamic parameters. There are presented several parameters that

on the dispersion of nanoadditive and the selection of dispersant.

Figure 12.

Figure 13.

79

and particles smaller than the valleys of the texture [63].

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

(wolfram disulfide) passes into a loaded contact.

technical system in which the lubricant will be introduced.

• rubbing with the third body—exfoliating nanoparticles and their outer layers gradually transfer to surface texture, providing easier friction under high load conditions, when the third body can be considered a mixture of oil, nanoparticles, and wear particles.

The use of nanoparticles as lubricant additives is a top issue of research in the last decades [43, 63].

A spherical nanoadditive in contact [63] could act like a damper between two asperities in contact. It could change its shape becoming flatter when the load increases, thus, protecting a larger surface against rubbing (Figures 11 and 12).

Jayadas et al. [64] calculated the advantage of using additives in oils, based on the results of the shear rate and the temperature influence on the viscosity of the additivated lubricant. Wu et al. [51] reported increased load capacity of the additivated lubricants. Many studies were based on a single concentration of the additive. The effect of varying viscosity due to nanoparticle concentration is difficult to model, and therefore, tests become relevant.

#### Figure 11.

Shape of a nanoparticle with the surface, under different operating regime [63]: punctual contact (low or no load), linear contact (mild load), and severe load (the move of surfaces one against another produces the shearing between additive and surface and not one among asperities).

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

#### Figure 12.

The effect of relative size of surface texture and additive particles: particle with similar dimensions as the profile and particles smaller than the valleys of the texture [63].

#### Figure 13.

to roll. The lubrication mechanism of nanoparticles as friction modifiers includes

The lubricating mechanism of water-based lubricants and TiO2 as an additive. (a) rolling effect, (b) mending

• rolling friction—spherical nanoparticles act as micro or nano ball roller bearings between triboelement surfaces under light load conditions,

• sliding—nanoparticles serve as spacers and eliminate direct metal/metal contact between the asperities of the two triboelements, under higher load

conditions, when the third body can be considered a mixture of oil,

• rubbing with the third body—exfoliating nanoparticles and their outer layers gradually transfer to surface texture, providing easier friction under high load

The use of nanoparticles as lubricant additives is a top issue of research in the

A spherical nanoadditive in contact [63] could act like a damper between two asperities in contact. It could change its shape becoming flatter when the load increases, thus, protecting a larger surface against rubbing (Figures 11 and 12). Jayadas et al. [64] calculated the advantage of using additives in oils, based on the results of the shear rate and the temperature influence on the viscosity of the additivated lubricant. Wu et al. [51] reported increased load capacity of the additivated lubricants. Many studies were based on a single concentration of the additive. The effect of varying viscosity due to nanoparticle concentration is diffi-

Shape of a nanoparticle with the surface, under different operating regime [63]: punctual contact (low or no load), linear contact (mild load), and severe load (the move of surfaces one against another produces the

three types of friction [62]:

Soybean - Biomass, Yield and Productivity

Figure 10.

conditions,

last decades [43, 63].

Figure 11.

78

nanoparticles, and wear particles.

effect, (c) polishing effect, and (d) effect of protective film [51].

cult to model, and therefore, tests become relevant.

shearing between additive and surface and not one among asperities).

Photos taken from the work of Lahouij et al. [65], the steps (here only two) through which a particle of WS2 (wolfram disulfide) passes into a loaded contact.

A study by Lahouij et al. in 2012 [65] shows how the WS2 (wolfram disulfide) particle protects the direct contact between metal asperities (Figure 13). The ovoid structure functions as a shock absorber and either the structure collapsed, or the particle was fragmented, it continued to remain between the two solid bodies. The hollow core of the particle was visible, and the deformation was large at the beginning of the stress, but as the load increased, the particle behaved like a variableelasticity spring, the elastic characteristic actually increasing. Then, the particle begins to tear or scissor, and, finally, the WS2 particle exfoliated in fragments.

From the studied literature, there is a tendency for deep research on additives in vegetal oils, especially those intended for lubrication. Attention should be focused on the dispersion of nanoadditive and the selection of dispersant.

## 3. Tribological characterization of lubricants based on soybean oil

#### 3.1 Tribological parameters and testing equipment related to lubricants

In order to assess the quality of lubricants, it is important to establish the test methodology (equipment, parameters, and investigations during and after testing). Their selection depends primarily on the practical use for which the lubricant is tested, and the selected tribotester should approach as much as possible to the technical system in which the lubricant will be introduced.

Tribological tests can be grouped in severe tests and tests under normal working conditions. The here-presented results could be appreciated as moderate regimes.

Depending on the future application and the researchers' abilities and knowledge, tribological characterization will be done by a set of parameters, one being insufficient for this purpose. The evaluation of the results is often done by accepting a compromise, as durability and reliability of a system are influenced by synergic effects of actual dynamic parameters. There are presented several parameters that

Figure 14. Four ball machine ("Lubritest" Laboratory, "Dunarea de Jos" University of Galati).

could be taken into account for evaluating tribological behavior, with particular reference to four-ball tester (Figure 14), even if there are other tribotesters used for establishing the lubricating capabilities of vegetal oils: pin-on-disc, ball-on-disc, reciprocating rigs [66], etc.

where R is the ball radius; WSD is the wear scar diameter (calculated as average

Wear rate of wear scar diameter is still rarely used, but it is more convenient for comparing results on four ball tribotester. Since the duration of the test is 1 h, the sliding distances are different for different speeds. For instance, for ball of 12.7 mm in diameter, tested 1 hour (this time being often selected by researchers), the sliding distance depends on the sliding speed in contact (that could be calculated knowing the rotational speed of the main shaft of the four ball machine): L(v = 0.38 m/s) = 1378.8 m; L(v = 0.53 m/s) = 1933.2 m; L(v = 0.69 m/s) = 2487 m. It is possible that the simple graph of the WSD dependence on additive concentration, load, and speed is not relevant due to the difference in the sliding distances, and then, on the basis of the literature [70], the wear can be also evaluated by another parameter

mm<sup>3</sup>

where ΔV is the variation in sample volume (volume of removed material), F is

the loading force; L is the sliding distance. The product F � L is the mechanical work done by the tribosystem; in other words, the wear rate shows the loss of material volume for the mechanical work unit performed by the system. The authors used a parameter named the wear rate of wear scar diameter, w(WSD),

where WSD is the wear scar diameter (calculated as average of six values of wear scars on fixed balls, along sliding and perpendicular to it), F is the load applied

Since Blok had developed the concept of "flash-temperature" [71] in 1963, even critical comments on the constraints and limitations characterizing the model have accepted that this parameter is strongly depending on the local peak of the heat flow generated by friction [72]. Flash temperature parameter (FTP) is related to the

<sup>=</sup>ð Þ <sup>N</sup> � <sup>m</sup> (2)

<sup>F</sup> � <sup>L</sup> ½ � mm=ð Þ <sup>N</sup> � <sup>m</sup> (3)

of six values of wear scars on fixed balls along sliding and perpendicular to it).

The sphere calotte for calculating the worn volume on a ball.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

<sup>w</sup> <sup>¼</sup> <sup>Δ</sup><sup>V</sup> F � L

w WSD ð Þ¼ WSD

on the four balls, L is the sliding distance.

called the wear rate, w:

Figure 15.

calculated as:

81

The coefficient of friction (COF) may be analyzed by the following parameters:


Several wear parameters for the tests done on four ball machine are given bellow:

Wear scar diameter (WSD) is the arithmetic average of the six diameter measurements, two on each of the three fixed balls of a test. For each ball, the wear diameter was measured in the direction of sliding and perpendicular to it. This value represents the diameter of the wear scar reported for each of the performed tests. The same method of obtaining the wear diameter is also given in specialized literature [66–68].

Wear as volume loss, considering the surface of wear scar as plane [69], is calculated as a sphere calotte having the diameter equal to the average wear scar diameter (see Figure 15):

$$\mathbf{V} = \boldsymbol{\pi} \cdot \boldsymbol{R}^3 \left( \mathbf{1} - \sqrt{\mathbf{1} - \frac{1}{4} \left( \frac{D}{R} \right)^2} \right)^2 \left[ \mathbf{1} - \frac{1}{3} \left( \mathbf{1} - \sqrt{\mathbf{1} - \frac{1}{4} \left( \frac{D}{R} \right)^2} \right) \right] \begin{bmatrix} \text{mm}^3 \end{bmatrix} \tag{1}$$

Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 15. The sphere calotte for calculating the worn volume on a ball.

where R is the ball radius; WSD is the wear scar diameter (calculated as average of six values of wear scars on fixed balls along sliding and perpendicular to it).

Wear rate of wear scar diameter is still rarely used, but it is more convenient for comparing results on four ball tribotester. Since the duration of the test is 1 h, the sliding distances are different for different speeds. For instance, for ball of 12.7 mm in diameter, tested 1 hour (this time being often selected by researchers), the sliding distance depends on the sliding speed in contact (that could be calculated knowing the rotational speed of the main shaft of the four ball machine): L(v = 0.38 m/s) = 1378.8 m; L(v = 0.53 m/s) = 1933.2 m; L(v = 0.69 m/s) = 2487 m. It is possible that the simple graph of the WSD dependence on additive concentration, load, and speed is not relevant due to the difference in the sliding distances, and then, on the basis of the literature [70], the wear can be also evaluated by another parameter called the wear rate, w:

$$
\omega = \frac{\Delta V}{F \times L} \,\left[\text{mm}^3/(\text{N}\cdot\text{m})\right] \tag{2}
$$

where ΔV is the variation in sample volume (volume of removed material), F is the loading force; L is the sliding distance. The product F � L is the mechanical work done by the tribosystem; in other words, the wear rate shows the loss of material volume for the mechanical work unit performed by the system. The authors used a parameter named the wear rate of wear scar diameter, w(WSD), calculated as:

$$\log(\text{WSD}) = \frac{\text{WSD}}{F \times L} \text{ [mm/(N} \cdot \text{m)]} \tag{3}$$

where WSD is the wear scar diameter (calculated as average of six values of wear scars on fixed balls, along sliding and perpendicular to it), F is the load applied on the four balls, L is the sliding distance.

Since Blok had developed the concept of "flash-temperature" [71] in 1963, even critical comments on the constraints and limitations characterizing the model have accepted that this parameter is strongly depending on the local peak of the heat flow generated by friction [72]. Flash temperature parameter (FTP) is related to the

could be taken into account for evaluating tribological behavior, with particular reference to four-ball tester (Figure 14), even if there are other tribotesters used for establishing the lubricating capabilities of vegetal oils: pin-on-disc, ball-on-disc,

Four ball machine ("Lubritest" Laboratory, "Dunarea de Jos" University of Galati).

• instantaneous value (i.e. at t time), paying attention to minimum and

samples per second being important in getting some peak values),

time intervals are considered to be a stabilized domain),

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi <sup>1</sup> � <sup>1</sup> 4

D R � �<sup>2</sup> 1 A

2

2 4

• average value over the last minutes of the test (argumentation: there are research reports presenting the average for 10 minutes, 5 minutes, as these

• variation interval of the friction coefficient for 1 hour and for the last 10

Several wear parameters for the tests done on four ball machine are given

Wear scar diameter (WSD) is the arithmetic average of the six diameter measurements, two on each of the three fixed balls of a test. For each ball, the wear diameter was measured in the direction of sliding and perpendicular to it. This value represents the diameter of the wear scar reported for each of the performed tests. The same method of obtaining the wear diameter is also given in specialized literature

Wear as volume loss, considering the surface of wear scar as plane [69], is calculated as a sphere calotte having the diameter equal to the average wear scar

1 �

@

0 s

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi <sup>1</sup> � <sup>1</sup> 4

D R � �<sup>2</sup> 1 A

3

<sup>5</sup> mm<sup>3</sup> � � (1)

The coefficient of friction (COF) may be analyzed by the following parameters:

• mean value over the duration of the test (1 hour in this study, the number of

reciprocating rigs [66], etc.

Soybean - Biomass, Yield and Productivity

Figure 14.

maximum values,

minutes.

bellow:

[66–68].

80

diameter (see Figure 15):

0 s

<sup>V</sup> <sup>¼</sup> <sup>π</sup> � <sup>R</sup><sup>3</sup> <sup>1</sup> �

@

critical flash temperature, above which a given lubricant does not operate in a convenient manner (it becomes ineffective) under the imposed conditions. Literature offers several relationships for calculating FTP, the authors selecting the one given by Marcher [72]:

$$FTP = \frac{F}{WSD^{1.4}} \left[ \text{N/mm}^{1.4} \right] \tag{4}$$

values of friction coefficient (COF) for the 1 hour testing on four ball machine are acceptable for the tested soybean oils (below 0.1), but generally higher than those for mineral oil, a proof for a thinner film generated in contact at least for the tested

Comparing the wear rates of WSD for the tested oils, one may notice that the two soybean oils produced lower values than those obtained with the transmission mineral oil T90, for the load range 100–200 N (see Figure 17). At F = 100 N, both vegetal oils are acceptable for actual applications, but at F = 200 N, FTP is almost double for vegetal oils as compared to T90 and at high speed, the degummed soybean oil becomes competitive. At highest speed and load, values of FTP are closer, above 800 N/mm1.4. T90 has a more pronounced increase of FTP with load and less with speed. This difference suggests the necessity of testing a lubricant and

Based on four ball test data, Georgescu concluded that the vegetal oils could be acceptable and comparable with nonadditivated mineral oils like T90 [75]. The degumming process makes this soybean oil to generate a more intense wear, meaning that the eliminated substances would have contributed to a better tribological behavior. The problem is that the coarse oil is less stable in time and exposed to oxidation. Values of COF are higher for the soybean oils suggesting a mixt or boundary regime, especially for load of 100 N. FTP was better, its values being greater than 1200 N/mm1.4 for soybean oils, under the load of 200 N. For F = 100–200 N, FTP for T90 was in the range 550–680 N/mm1.4. For F = 300 N, this parameter is kept at 1000–1200 N/mm1.4 for all tested oils, only for speeds of 0.46 m/s and 0.57 m/s. The conclusion of the study presented by Georgescu [75] is that these two soybean

oils could be used as lubricants for low loads and moderate speeds, and the degumming process does not influence significantly the tribological behavior, at least for the tested regimes, as evidenced by FTP values in Figure 18 and by those for OFS in Figure 19. Each parameter has values in a narrow range for both coarse and degummed soybean oils. The higher difference in FTP for these soybean oils

Influence of load and sliding speed on the average value of COF [75]. (a) Coarse soybean oil (cold pressed). (b)

parameters (Figure 16).

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 16.

83

Degummed soybean oil. (c) Transmission oil T90.

not to estimate by general considerations.

where F is the applied load on the four ball tribotester, in N; WSD is the average of the six measured wear scar diameters on the fixed balls in one test. Under constant load, there is an indirect proportionality between FTP and wear scar diameter.

FTP allows for evaluating the lubrication capacity of a fluid, especially under high loads, as these generate high temperature on rubbing surfaces, as it is the case of rolling mill and cutting processes. For a lubricant, FTP reflects the lowest temperature at which the liquid evaporates, risking auto-ignition in air. High values of this parameter are associated with a positive characteristic of a lubricant as it does not evaporate if the temperature in contact is low and the fluid film is thick enough to reduce friction and to avoid direct contact of asperities. Thus, the heat flow generated by friction will not be so high. These low temperatures and a reduced friction may also characterize boundary lubrication. Low values of FTP indicate the damage of the fluid film.

Oil film strength (OFS) is calculated using the load on a contact between the mobile and fix balls, Q , in N:

$$\text{OFS} = \frac{Q}{A\_s} = \frac{0.408 \cdot F}{A\_s} = \frac{1.632 \cdot F}{\pi \cdot WSD^2} \tag{5}$$

$$Q = \frac{F}{3\cos\theta} \cong 0.408 \cdot F \tag{6}$$

F is the applied load on the four ball tribotester, [N]; θ is the angle between the load direction on the main shaft of the four ball machine and the direction of normal load in the contact between the rotating ball and one fixed ball (θ ≈ 35.264°); As is wear area, calculated with the average WSD for the three fixed balls [mm<sup>2</sup> ].

Maps in tribological analysis are useful in assessing trends and determining test regimens for which two or more variables influence the tribological parameters; thus, the tribological behavior of the system is better revealed.

Investigations of the worn surfaces and used lubricants could be done with the help of FTIR (Fourier Transform Infrared) spectrometry, 3D profilometry [73, 74].

#### 3.2 Tribological characteristics of soybean oil

Lubricant properties influence the tribological behavior of a system, one of the most important being the dynamic viscosity.

Georgescu presented a report [75] on different grade of rapeseed and soybean oils. The antiwear characteristics were tested for the following parameters: load on four ball tester—100 N, 200 N, and 300 N; sliding speed—0.46 m/s (1200 rpm), 0.57 m/s (1500 rpm), and 0.69 m/s (1800 rpm); test duration—60 minutes (rpm rotations per minute of the main shaft of the four ball machine). Balls, as delivered by SKF (Swedish Ball Bearing Factory), are mirror-finished, with the arithmetic mean of absolute values of the ordinates z(x), measured from the mean line Ra = 0.02–0.03 μm and made of EN31 steel grade (also named 100Cr6) steel grade, having a hardness of 60–66 HRC and a diameter of 12.7 � 0.0005 mm. Average

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

critical flash temperature, above which a given lubricant does not operate in a convenient manner (it becomes ineffective) under the imposed conditions. Literature offers several relationships for calculating FTP, the authors selecting the one

of the six measured wear scar diameters on the fixed balls in one test. Under constant load, there is an indirect proportionality between FTP and wear scar

where F is the applied load on the four ball tribotester, in N; WSD is the average

FTP allows for evaluating the lubrication capacity of a fluid, especially under high loads, as these generate high temperature on rubbing surfaces, as it is the case of rolling mill and cutting processes. For a lubricant, FTP reflects the lowest temperature at which the liquid evaporates, risking auto-ignition in air. High values of this parameter are associated with a positive characteristic of a lubricant as it does not evaporate if the temperature in contact is low and the fluid film is thick enough to reduce friction and to avoid direct contact of asperities. Thus, the heat flow generated by friction will not be so high. These low temperatures and a reduced friction may also characterize boundary lubrication. Low values of FTP

Oil film strength (OFS) is calculated using the load on a contact between the

<sup>¼</sup> <sup>0</sup>:<sup>408</sup> � <sup>F</sup> As

F is the applied load on the four ball tribotester, [N]; θ is the angle between the load direction on the main shaft of the four ball machine and the direction of normal load in the contact between the rotating ball and one fixed ball (θ ≈ 35.264°); As is wear area, calculated with the average WSD for the three fixed balls [mm<sup>2</sup>

Maps in tribological analysis are useful in assessing trends and determining test regimens for which two or more variables influence the tribological parameters;

Investigations of the worn surfaces and used lubricants could be done with the help of FTIR (Fourier Transform Infrared) spectrometry, 3D profilometry [73, 74].

Lubricant properties influence the tribological behavior of a system, one of the

Georgescu presented a report [75] on different grade of rapeseed and soybean oils. The antiwear characteristics were tested for the following parameters: load on four ball tester—100 N, 200 N, and 300 N; sliding speed—0.46 m/s (1200 rpm), 0.57 m/s (1500 rpm), and 0.69 m/s (1800 rpm); test duration—60 minutes (rpm rotations per minute of the main shaft of the four ball machine). Balls, as delivered by SKF (Swedish Ball Bearing Factory), are mirror-finished, with the arithmetic mean of absolute values of the ordinates z(x), measured from the mean line Ra = 0.02–0.03 μm and made of EN31 steel grade (also named 100Cr6) steel grade, having a hardness of 60–66 HRC and a diameter of 12.7 � 0.0005 mm. Average

<sup>¼</sup> <sup>1</sup>:<sup>632</sup> � <sup>F</sup>

<sup>π</sup> � WSD<sup>2</sup> (5)

].

ffi 0:408 � F (6)

WSD1:<sup>4</sup> <sup>N</sup>=mm1:<sup>4</sup> (4)

FTP <sup>¼</sup> <sup>F</sup>

given by Marcher [72]:

Soybean - Biomass, Yield and Productivity

indicate the damage of the fluid film.

OFS <sup>¼</sup> <sup>Q</sup> As

thus, the tribological behavior of the system is better revealed.

3.2 Tribological characteristics of soybean oil

most important being the dynamic viscosity.

82

<sup>Q</sup> <sup>¼</sup> <sup>F</sup> 3 cos θ

mobile and fix balls, Q , in N:

diameter.

values of friction coefficient (COF) for the 1 hour testing on four ball machine are acceptable for the tested soybean oils (below 0.1), but generally higher than those for mineral oil, a proof for a thinner film generated in contact at least for the tested parameters (Figure 16).

Comparing the wear rates of WSD for the tested oils, one may notice that the two soybean oils produced lower values than those obtained with the transmission mineral oil T90, for the load range 100–200 N (see Figure 17). At F = 100 N, both vegetal oils are acceptable for actual applications, but at F = 200 N, FTP is almost double for vegetal oils as compared to T90 and at high speed, the degummed soybean oil becomes competitive. At highest speed and load, values of FTP are closer, above 800 N/mm1.4. T90 has a more pronounced increase of FTP with load and less with speed. This difference suggests the necessity of testing a lubricant and not to estimate by general considerations.

Based on four ball test data, Georgescu concluded that the vegetal oils could be acceptable and comparable with nonadditivated mineral oils like T90 [75]. The degumming process makes this soybean oil to generate a more intense wear, meaning that the eliminated substances would have contributed to a better tribological behavior. The problem is that the coarse oil is less stable in time and exposed to oxidation.

Values of COF are higher for the soybean oils suggesting a mixt or boundary regime, especially for load of 100 N. FTP was better, its values being greater than 1200 N/mm1.4 for soybean oils, under the load of 200 N. For F = 100–200 N, FTP for T90 was in the range 550–680 N/mm1.4. For F = 300 N, this parameter is kept at 1000–1200 N/mm1.4 for all tested oils, only for speeds of 0.46 m/s and 0.57 m/s. The conclusion of the study presented by Georgescu [75] is that these two soybean oils could be used as lubricants for low loads and moderate speeds, and the degumming process does not influence significantly the tribological behavior, at least for the tested regimes, as evidenced by FTP values in Figure 18 and by those for OFS in Figure 19. Each parameter has values in a narrow range for both coarse and degummed soybean oils. The higher difference in FTP for these soybean oils

#### Figure 16.

Influence of load and sliding speed on the average value of COF [75]. (a) Coarse soybean oil (cold pressed). (b) Degummed soybean oil. (c) Transmission oil T90.

### Figure 17.

Influence of load and sliding speed on the wear rate of WSD (wear scar diameter) [75]. (a) Coarse soybean oil (cold pressed). (b) Degummed soybean oil. (c) Transmission oil T90.

and 1%wt). Figure 20 presents scanning electron microscopy (SEM images) for the

• nanoamorphous carbon—average particle size 13 nm, specific surface area

• graphene—nanoplates with a thickness of 1.4 nm and a particle size of up to 2 μm.

Figure 21 presents the evolution of COF over time, depending on load and speed, for two tests with the same parameters (F, v) when the four ball tribotester is lubricated with soybean oil. One may notice that, at the tested highest speed (v = 0.69 m/s), COF is less influenced by the applied load and performs in a narrow range meaning that speed is more important in generating a continuous fluid film, as argued by Dowson and Higginson for elasto-hydrodynamic lubrication [37].

Scanning electron microscopy for nanoparticles added in soybean oil [41]. (a) Black carbon. (b) Graphite.

nanoadditives that were supplied by PlasmaChem [76]:

Influence of load and sliding speed on the oil film strength (OFS) [75].

• nanographite—average particle radius 400–450 nm,

550 m<sup>2</sup>

Figure 19.

Figure 20.

85

(c) Graphene.

/g,

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

was noticed only for moderate load and that could be explained by the presence of gummy products in coarse soybean oil.

Cristea [41] reported the tribological behavior of soybean oil and soybean oil additivated with carbon-base nanoparticles, in different concentration (0.25, 0.5,

#### Figure 18.

FTP as function of load and sliding speed [75]. SB—coarse soybean oil, SBD—degummed soybean oil, T90—transmission oil. (a) 100 N. (b) 200 N. (c) 300 N.

Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 19. Influence of load and sliding speed on the oil film strength (OFS) [75].

and 1%wt). Figure 20 presents scanning electron microscopy (SEM images) for the nanoadditives that were supplied by PlasmaChem [76]:


Figure 21 presents the evolution of COF over time, depending on load and speed, for two tests with the same parameters (F, v) when the four ball tribotester is lubricated with soybean oil. One may notice that, at the tested highest speed (v = 0.69 m/s), COF is less influenced by the applied load and performs in a narrow range meaning that speed is more important in generating a continuous fluid film, as argued by Dowson and Higginson for elasto-hydrodynamic lubrication [37].

Figure 20.

Scanning electron microscopy for nanoparticles added in soybean oil [41]. (a) Black carbon. (b) Graphite. (c) Graphene.

was noticed only for moderate load and that could be explained by the presence of

Influence of load and sliding speed on the wear rate of WSD (wear scar diameter) [75]. (a) Coarse soybean oil

Cristea [41] reported the tribological behavior of soybean oil and soybean oil additivated with carbon-base nanoparticles, in different concentration (0.25, 0.5,

FTP as function of load and sliding speed [75]. SB—coarse soybean oil, SBD—degummed soybean oil,

T90—transmission oil. (a) 100 N. (b) 200 N. (c) 300 N.

gummy products in coarse soybean oil.

Soybean - Biomass, Yield and Productivity

(cold pressed). (b) Degummed soybean oil. (c) Transmission oil T90.

Figure 17.

Figure 18.

84

The values of friction coefficient for all six oils (Figure 24a) show no clear trend. At 25°C and all speed conditions, epoxidized soybean oil without an antiwear additive has the highest friction coefficient. This is due to the fact that viscosity of

The wear scars obtained with the soybean oil without additives v = 0.69 m/s [41].

Refined soybean oil [41]

Soybean oil [78]

C16:1 0.13 0.15

C17:0 0.05 0.15

Miritic acid C14:0 0.11 0.1 Palmitic acid C16:0 12.7 10.5 7 15

Stearic acid C18:0 5.40 4.1 4 6.78 Oleic acid C18:1 21.60 23.4 83 26.6 Linoleic acid C18:2 52.40 52.6 3 46.3 Linolenic acid C18:3 5.70 7.2 2 2.69 Arachidic acid C20:0 0.25 0.61

Influence of different grades of soybean oil on friction coefficient (a) and wear scar diameter (b). Test conditions: 0.5 h, F = 110 N, v = 900 rpm, NSB—normal soybean oil, ESB—epoxidized soybean oil, HSB

High oleic soybean oil [78]

Soybean oil [79]

Fatty acid Symbol Concentration, %wt

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

Gondoic acid C20:1 0.20

C20:2 0.50

—high-oleic soybean oil, +AW—additivated with 1% ZDDP [78].

The characteristic fatty acid composition for the soybean oil, modified or not.

Figure 23.

Palmitoleic acid

Heptadecanoic acid

Eicosadenic acid

Table 4.

Figure 24.

87

Figure 21.

The evolution of COF over time, depending on load and speed, for two tests with the same parameters (F, v) [41].

A representation of the wear rate of WSD (Figure 22) helps the researcher to observe the evolution trends of the parameter of interest according to two variables, here the tribotester load and the sliding speed of the rotating ball on the three fixed balls. For the range of analyzed loads and speeds, nonadditivated soybean oil had a downward trend with increasing load and speed. This trend is also consistent with Dowson and Higginson's argument on generating the elasto-hydrodynamic film [37] as wear will be reduced if the fluid film interposes between solid triboelements. They have shown that the speed factor U ¼ η0ð Þ U<sup>1</sup> þ U<sup>2</sup> = 2E 0 � Re has the greatest influence on the minimum thickness of the fluid. For low-viscosity oils, the material factor G (α � E 0 ) cannot participate in film formation to the same extent as the viscous oils at the working temperature of the contact [77]. (U1, U2 are the relative speeds of triboelements in contact, η<sup>0</sup> is the lubricat viscosity at areference temperature, E 0 is the equivalent Young modulus of the solid elements and, Re is the equivalent radius of the contacting surfaces, α is the pressure-viscosity coefficient of the lubricant). In addition, vegetal oils are characterized by a high viscosity index, that is, the variation of this characteristic with the temperature is low, especially at temperatures above 50–60°C (see Figure 4). Images of wear scars in Figure 23 point out a change of texture quality, especially when load increases to F = 300 N, even if the wear rate of WSD is the lowest for this load and all the tested speeds.

Cheenkachorn [78] studied three types of soybean oils (two given in Table 4, the third being an epoxidized soybean oil is simply the conventional soybean oil, in which all double bonds are epoxidized to form epoxide rings. Each of these oils was additivated with 1% ZDDP (Zinc dialkyldithiophosphates).

Figure 22. Wear rate of WSD for the nonadditivated soybean oil [41].

The values of friction coefficient for all six oils (Figure 24a) show no clear trend. At 25°C and all speed conditions, epoxidized soybean oil without an antiwear additive has the highest friction coefficient. This is due to the fact that viscosity of

Figure 23.

A representation of the wear rate of WSD (Figure 22) helps the researcher to observe the evolution trends of the parameter of interest according to two variables, here the tribotester load and the sliding speed of the rotating ball on the three fixed balls. For the range of analyzed loads and speeds, nonadditivated soybean oil had a downward trend with increasing load and speed. This trend is also consistent with Dowson and Higginson's argument on generating the elasto-hydrodynamic film [37] as wear will be reduced if the fluid film interposes between solid triboelements. They

The evolution of COF over time, depending on load and speed, for two tests with the same parameters

ence on the minimum thickness of the fluid. For low-viscosity oils, the material factor

the equivalent Young modulus of the solid elements and, Re is the equivalent radius of the contacting surfaces, α is the pressure-viscosity coefficient of the lubricant). In addition, vegetal oils are characterized by a high viscosity index, that is, the variation of this characteristic with the temperature is low, especially at temperatures above 50–60°C (see Figure 4). Images of wear scars in Figure 23 point out a change of texture quality, especially when load increases to F = 300 N, even if the wear rate of

Cheenkachorn [78] studied three types of soybean oils (two given in Table 4, the third being an epoxidized soybean oil is simply the conventional soybean oil, in which all double bonds are epoxidized to form epoxide rings. Each of these oils was

the working temperature of the contact [77]. (U1, U2 are the relative speeds of triboelements in contact, η<sup>0</sup> is the lubricat viscosity at areference temperature, E

) cannot participate in film formation to the same extent as the viscous oils at

0 � Re

has the greatest influ-

0 is

have shown that the speed factor U ¼ η0ð Þ U<sup>1</sup> þ U<sup>2</sup> = 2E

WSD is the lowest for this load and all the tested speeds.

additivated with 1% ZDDP (Zinc dialkyldithiophosphates).

Wear rate of WSD for the nonadditivated soybean oil [41].

G (α � E 0

Figure 22.

86

Figure 21.

Soybean - Biomass, Yield and Productivity

(F, v) [41].

The wear scars obtained with the soybean oil without additives v = 0.69 m/s [41].


#### Table 4.

The characteristic fatty acid composition for the soybean oil, modified or not.

#### Figure 24.

Influence of different grades of soybean oil on friction coefficient (a) and wear scar diameter (b). Test conditions: 0.5 h, F = 110 N, v = 900 rpm, NSB—normal soybean oil, ESB—epoxidized soybean oil, HSB —high-oleic soybean oil, +AW—additivated with 1% ZDDP [78].

epoxidized soybean oil is higher than those of conventional soybean oil and higholeic soybean oil. When the temperature increases, the viscosity of epoxidized soybean oil decreases. This results in a better oil circulation and forming of a multiple-layer film, which reduces the friction coefficient.

oil produces a decrease of WSD as compared to that produced by soybean oil. The friction coefficient seems to depend on the polymerization process, its values being less influenced by the load for the soybean oil PSO2. These better results for PSO2 may be explained by the nitrogen content, higher for PSO2, as result of a different

The problem to be solved with such antiwear additives is their dispersion in oil. Cristea [41] proposed a method of obtaining a good dispersion taking into account that the tested base oil is a mixture of fatty acid triglycerides (see Table 4, first

• mechanical mixing of the additive and an equal amount of guaiacol (supplied

• gradually adding the soybean oil, measured to obtain 200 g of lubricant with the desired additive concentration (0.25%wt, 0.5%wt or 1%wt), by mixing

• ultrasonication + cooling: 200 g of lubricant for 5 minutes using the Bandelin HD 3200 sonicator (Electronic GmbH & KG Berlin) sonicator; the lubricants are heated to about 70°C; the cooling time was 1 hour; this ultrasonic + cooling step is repeated five times to obtain a total of 60 minutes of sonication. The

parameters of the ultrasonic regime are: 100 W power, frequency

Particles of nanoblack carbon on wear scar. Test conditions: v = 0.38 m/s, F = 200 N, time 1 h, lubricant:

methoxyphenol) for 20 minutes; this dispersing agent is compatible with both the additive and the soybean oil (the mass ratio of the additive in the dispersing

by Fluka Chemica) with the chemical formula C6H4(OH)OCH3 (2-

time of polymerization.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

3.3 Soybean additivation with carbonic materials

3.3.1 Laboratory formulations of additivated lubricants

agent is 1:1, with an accuracy of 0.1 mg);

with a magnetic homogenizer during 1 h;

20 kHz 500 Hz, continuous mode.

Figure 26.

89

soybean oil +1% nanoblack carbon [47].

column). The steps followed in this laboratory technology were:

When comparing the results obtained by Cristea for refined soybean oil (see the first column in Table 4) with balls with very close characteristics [41], but for 1 hour test, 100 N at 1000 rpm, the higher value of WSD (0.413 mm) was just a little bit higher than that obtained by Cheenkachorn [78] for half testing time, meaning that during a longer time test, the wearing process is more intense especially in the beginning of the test, and the wearing process is slowing down due to lubricity of the lubricant (boundary lubrication) but also to the accommodation of surface textures in contact. ZDDP showed no clear influence on the trend of friction coefficient. For epoxidized soybean oil and high-oleic soybean oil, the temperature predominantly affected the wear scar diameters. This additive introduced in tested vegetal oils makes the temperature to have less influence on WSD (Figure 24b), and this being explained by the protection offered by the additive to the rubbing textures of the balls.

Zhao et al. [79] tested two types of oils with high viscosity, synthesized by nitrogen plasma polymerization of soybean oil. The nitrogen atoms were incorporated into the molecule of polymerized oil, and these three nitrogen heterocyclic compounds played a key role in improving tribological characteristics of polymerized oils. The lubricating properties of polymerized oils were tested on the four ball tester. The load-carrying capacities of polymerized oils reached 940.8 and 1049 N, respectively, higher than that of the unmodified soybean oil (646.8 N). They showed better antiwear properties under all tested loads and possessed preferable friction-reducing performances when the applied load surpassed 250 N. It was found that the nitrogen heterocyclic structure containing six atoms of nitrogen possessed higher coordination capacity than the ester groups of soybean oil and could form a durable organic nitrogen complex film on the metal surface. Simultaneously, the blended oils with different viscosity grades, which were prepared by diluting the polymerized oil with dioctyl sebacate, show excellent receptivity on the antiwear/extreme pressure additives of zinc dialkyl dithiophosphates and sulfurized isobutylene. Nitrogen plasma was used to open the C=C of soybean oil for polymerization. The values of kinematic viscosity (at 40°C) of the two polymerized soybean oils (PSO1 and PSO2) increased to 285 cSt (100 cSt = 1 cm<sup>2</sup> /s) and 576 cSt from 33.8 cSt, respectively, and the viscosity indexes of PSO1 and PSO2 reached 220 and 283, respectively. The tribological characteristics (wear scar diameter and friction coefficient) are given in Figure 25, showing that the polymerization of soybean

#### Figure 25.

Tribological characteristics of soybean oil, polymerized soybean oils (PSO1 and PSO2) and 150BS (industrial mineral oil with kinematic viscosity 601 cSt at 40°C and 31.4 cSt at 100°C, viscosity index 77) at different loads [79]: wear scar diameter (a), friction coefficient (b).

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

epoxidized soybean oil is higher than those of conventional soybean oil and higholeic soybean oil. When the temperature increases, the viscosity of epoxidized soybean oil decreases. This results in a better oil circulation and forming of a

When comparing the results obtained by Cristea for refined soybean oil (see the first column in Table 4) with balls with very close characteristics [41], but for 1 hour test, 100 N at 1000 rpm, the higher value of WSD (0.413 mm) was just a little bit higher than that obtained by Cheenkachorn [78] for half testing time, meaning that during a longer time test, the wearing process is more intense especially in the beginning of the test, and the wearing process is slowing down due to lubricity of the lubricant (boundary lubrication) but also to the accommodation of surface textures in contact. ZDDP showed no clear influence on the trend of friction coefficient. For epoxidized soybean oil and high-oleic soybean oil, the temperature predominantly affected the wear scar diameters. This additive introduced in tested vegetal oils makes the temperature to have less influence on WSD (Figure 24b), and this being explained

by the protection offered by the additive to the rubbing textures of the balls. Zhao et al. [79] tested two types of oils with high viscosity, synthesized by nitrogen plasma polymerization of soybean oil. The nitrogen atoms were incorporated into the molecule of polymerized oil, and these three nitrogen heterocyclic compounds played a key role in improving tribological characteristics of polymerized oils. The lubricating properties of polymerized oils were tested on the four ball tester. The load-carrying capacities of polymerized oils reached 940.8 and 1049 N, respectively, higher than that of the unmodified soybean oil (646.8 N). They showed better antiwear properties under all tested loads and possessed preferable friction-reducing performances when the applied load surpassed 250 N. It was found that the nitrogen heterocyclic structure containing six atoms of nitrogen possessed higher coordination capacity than the ester groups of soybean oil and could form a durable organic nitrogen complex film on the metal surface. Simultaneously, the blended oils with different viscosity grades, which were prepared by diluting the polymerized oil with dioctyl sebacate, show excellent receptivity on the antiwear/extreme pressure additives of zinc dialkyl dithiophosphates and sulfurized isobutylene. Nitrogen plasma was used to open the C=C of soybean oil for polymerization. The values of kinematic viscosity (at 40°C) of the two polymerized

soybean oils (PSO1 and PSO2) increased to 285 cSt (100 cSt = 1 cm<sup>2</sup>

Figure 25.

88

loads [79]: wear scar diameter (a), friction coefficient (b).

from 33.8 cSt, respectively, and the viscosity indexes of PSO1 and PSO2 reached 220 and 283, respectively. The tribological characteristics (wear scar diameter and friction coefficient) are given in Figure 25, showing that the polymerization of soybean

Tribological characteristics of soybean oil, polymerized soybean oils (PSO1 and PSO2) and 150BS (industrial mineral oil with kinematic viscosity 601 cSt at 40°C and 31.4 cSt at 100°C, viscosity index 77) at different

/s) and 576 cSt

multiple-layer film, which reduces the friction coefficient.

Soybean - Biomass, Yield and Productivity

oil produces a decrease of WSD as compared to that produced by soybean oil. The friction coefficient seems to depend on the polymerization process, its values being less influenced by the load for the soybean oil PSO2. These better results for PSO2 may be explained by the nitrogen content, higher for PSO2, as result of a different time of polymerization.

## 3.3 Soybean additivation with carbonic materials

## 3.3.1 Laboratory formulations of additivated lubricants

The problem to be solved with such antiwear additives is their dispersion in oil. Cristea [41] proposed a method of obtaining a good dispersion taking into account that the tested base oil is a mixture of fatty acid triglycerides (see Table 4, first column). The steps followed in this laboratory technology were:


Figure 26.

Particles of nanoblack carbon on wear scar. Test conditions: v = 0.38 m/s, F = 200 N, time 1 h, lubricant: soybean oil +1% nanoblack carbon [47].

The method of sonication was also used for getting an acceptable dispersion of nanoparticles in lubricants by [80, 81].

evolution of the friction coefficient over time is based on the comments done by Czikos [66]. Thus, the coefficient for the soybean oil with nanocarbon is spread on a large interval for the lowest speed, but at v = 0.69 m/s, after a period with high values, COF performs in a narrow interval, under 0.06, meaning a full lubrication (Figure 27). For additivated lubricants, the tendency is to reduce the friction

Analyzing Figure 28, it is noted that at a concentration of 1.0% of nanocarbon, the

(v = 0.69 m/s). Under the minimum test load (F = 100 N), the COF oscillation range is the largest. Also, this regime gives less influence on wear rate of WSD (see Figure 30). For nanocarbon additivated lubricants, average values of COF below 0.1 were obtained for all tests, except for the regime F = 100 N, v = 0.38 m/s, and v = 0.53 m/s and for F = 300 N, v = 0.38 m/s but just a little over 0.1. Addition of nanocarbon in soybean oil resulted in a COF decreasing trend for extreme test regimes ([F = 100 N, v = 0.38 m/s] and [F = 300 N, v = 0.69 m/s]). In the remaining combinations of test

This antiwear additive does not have a very clear influence on improving the tribological behavior of the soybean oil. Although the friction reduction mechanism

exists in the presence of the additive, which is the interposition of carbon nanoparticles between the friction surfaces, as a third body friction, due to the migration of these particles (because they are not bonded to the surfaces) and to their uneven distribution in the contact, the tribosystem behaves more unstable than that using neat soybean oil. In a statistical approach, at some time moment and area of the contact, it could come in contact with particles sufficiently to reduce friction and wear, but during operation, there could be times when this number is low enough to have a mixt contact, and the oscillations between these two situations could explain the variations in friction coefficient and higher values for WSD.

Wear rate of wear scar diameter (WSD) for amorphous nanocarbon-additivated lubricants [41].

Wear scar obtained with soybean oil +0.25% nanocarbon, F = 300 N (optical microscopy) [82]: v = 0.38 m/s

friction coefficient becomes lower for higher load (F = 300 N) and high speed

coefficient after a period of operation of 10–15 minutes.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

parameters, the influence of additivation on COF is not obvious.

Figure 30.

91

Figure 29.

(a), v = 0.53 m/s (b), v = 0.69 m/s (c)

### 3.3.2 Soybean oil additivated with nano carbon

Investigations by the help of scanning electron microscopy show that nanocarbon particles are on the friction surfaces as nanoagglomerations (Figure 26), on the surface texture of the wear scar. These particles or agglomerations appear to be rolled up and are likely to act as nanorolling elements, which explain low friction coefficients during the test (see Figures 27 and 28). The problem is that these particles are not uniformly distributed over the contact surfaces, producing a preferential wear on the particle-free areas. As the particles migrate in motion, these areas are prone to direct contact. This may be the explanation for the variation of the friction coefficient over time and with large amplitudes (Figure 27) and the variation of the average value of friction coefficient in larger ranges (Figure 28).

The friction coefficient plots of Figure 27 are done using a moving average of 200 values, the recorded samples being of 2 values per second. The discussion of the

Figure 27.

The evolution of COF over time, depending on load and sliding speed for two tests with the same parameters (F, v) Cristea [82].

Figure 28.

Average values of friction coefficient (COF) during a test of 1 hour (two tests with the same parameters) [82].

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

The method of sonication was also used for getting an acceptable dispersion of

Investigations by the help of scanning electron microscopy show that nanocarbon

The friction coefficient plots of Figure 27 are done using a moving average of 200 values, the recorded samples being of 2 values per second. The discussion of the

The evolution of COF over time, depending on load and sliding speed for two tests with the same parameters

Average values of friction coefficient (COF) during a test of 1 hour (two tests with the same parameters) [82].

particles are on the friction surfaces as nanoagglomerations (Figure 26), on the surface texture of the wear scar. These particles or agglomerations appear to be rolled up and are likely to act as nanorolling elements, which explain low friction coefficients during the test (see Figures 27 and 28). The problem is that these particles are not uniformly distributed over the contact surfaces, producing a preferential wear on the particle-free areas. As the particles migrate in motion, these areas are prone to direct contact. This may be the explanation for the variation of the friction coefficient over time and with large amplitudes (Figure 27) and the variation of the average

nanoparticles in lubricants by [80, 81].

Soybean - Biomass, Yield and Productivity

Figure 27.

Figure 28.

90

(F, v) Cristea [82].

3.3.2 Soybean oil additivated with nano carbon

value of friction coefficient in larger ranges (Figure 28).

evolution of the friction coefficient over time is based on the comments done by Czikos [66]. Thus, the coefficient for the soybean oil with nanocarbon is spread on a large interval for the lowest speed, but at v = 0.69 m/s, after a period with high values, COF performs in a narrow interval, under 0.06, meaning a full lubrication (Figure 27). For additivated lubricants, the tendency is to reduce the friction coefficient after a period of operation of 10–15 minutes.

Analyzing Figure 28, it is noted that at a concentration of 1.0% of nanocarbon, the friction coefficient becomes lower for higher load (F = 300 N) and high speed (v = 0.69 m/s). Under the minimum test load (F = 100 N), the COF oscillation range is the largest. Also, this regime gives less influence on wear rate of WSD (see Figure 30).

For nanocarbon additivated lubricants, average values of COF below 0.1 were obtained for all tests, except for the regime F = 100 N, v = 0.38 m/s, and v = 0.53 m/s and for F = 300 N, v = 0.38 m/s but just a little over 0.1. Addition of nanocarbon in soybean oil resulted in a COF decreasing trend for extreme test regimes ([F = 100 N, v = 0.38 m/s] and [F = 300 N, v = 0.69 m/s]). In the remaining combinations of test parameters, the influence of additivation on COF is not obvious.

This antiwear additive does not have a very clear influence on improving the tribological behavior of the soybean oil. Although the friction reduction mechanism exists in the presence of the additive, which is the interposition of carbon nanoparticles between the friction surfaces, as a third body friction, due to the migration of these particles (because they are not bonded to the surfaces) and to their uneven distribution in the contact, the tribosystem behaves more unstable than that using neat soybean oil. In a statistical approach, at some time moment and area of the contact, it could come in contact with particles sufficiently to reduce friction and wear, but during operation, there could be times when this number is low enough to have a mixt contact, and the oscillations between these two situations could explain the variations in friction coefficient and higher values for WSD.

#### Figure 29.

Wear scar obtained with soybean oil +0.25% nanocarbon, F = 300 N (optical microscopy) [82]: v = 0.38 m/s (a), v = 0.53 m/s (b), v = 0.69 m/s (c)

Figure 30.

Wear rate of wear scar diameter (WSD) for amorphous nanocarbon-additivated lubricants [41].

Since particle distribution is not even in contact during operation, this type of antiwear additive cannot help to improve tribological behavior because it does not reduce the friction coefficient and does not reduce the WSD as compared to those produce with neat soybean oil. The authors believe that the additive should be bonded (physically or chemically) for better results.

From Figure 29, it is noticed that the wear pattern did not increase too much with the speed, but the quality of the surface has considerably worsened, which justifies the profilometry study in [41, 73].

The wear rate of wear scar diameter, w(WSD), helps to determine the influence of the concentration of this nanoadditive. In graphs in Figure 30, the neat oil is not given. The additive, either with 0.25% or 1%, makes the wear parameter to visibly decrease with speed only for low load (F = 100N). Comparison with nonadditivated soybean oil is highlighted on the maps in Figure 39, where 0% additive concentration is for the neat oil. It can be noted a decrease of w(WSD) with load for all concentrations and speeds, for the additivated lubricants; the slope of the speed dependence for the same load is lower. At v = 0.38 m/s, the influence of the additive concentration is insignificant and the additivation would be justified in the field of high force for all speeds.

For nanocarbon additivated lubricants, w(WSD) is less sensitive to additive concentration, especially for F = 300 N. The nonadditivated soybean oil can be recommended for light regimes (equivalent to F = 100–200 N and speed v = 0.38– 0.69 m/s). The almost linear dependence of WSD on the concentration of this additive is only observed for combinations with F = 100 N. For the tested regimes (F = 100–300 N and v = 0.38–0.69 m/s), the results are not in the favor of nanocarbon additivation of the soybean oil.

ones due to load and surface texture). It appears that the presence of graphite prevents the generation of EHL (elasto-hydrodinamic lubrication) film as COF has higher values, toward 0.1, especially for F = 300 N. No lower average COF values than those for the soybean oil have been obtained, except for tests: (F = 100 N, v = 0.38 m/s) and (F = 100 N, v = 0.53 m/s), with a graphite concentration of 0.25%wt. But the differences are too small to highlight an influence of the additive or the test regime. High values for wear rate of WSD at low load and speed imply more intense abrasion, which occurs if the lubricant film does not form and/or if the additive does not protect the contact. Maybe local particle agglomerations make the friction

Average values and scattering intervals for two tests performed with the same parameters (F, v, c) [82, 83].

coefficient to oscillate and, when they migrate in contact, they allow one

not encountered the graphite agglomerations.

Figure 32.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 33.

93

with rare adhesive wear spots at higher loads.

Photos of the wear scars of the soybean oil +1% nanographite [82].

triboelement to fall over the other, in direct contact under higher load than if it had

Analyzing the photos in Figure 33, it can be noticed that the nature of the wear pattern does not change significantly, resulting from the abrasive wear process and

### 3.3.3 Soybean oil additivated with nanographite

Figure 31 shows the evolution over time of COF for all tests performed with soybean oil additivated with nanographite. There is a narrowing of its evolution range for v = 0.69 m/s for all loads and a scattering of higher COF values for low speeds and loads.

Analyzing Figure 32, it can be noticed that, at F = 100 N (first horizontal line), the nanoadditive does not dramatically alter COF average. At high load (F = 300 N), COF increased for all additivated soybean oils as compared to the neat oil. The explanation would be that the graphite does not cover the entire surface of the contact but is only present in contact in the form of nanorolls, the reduced friction being zonal. There are also direct friction areas and friction areas with the third body (where nanoparticles or microparticles generated by agglomerating the first

#### Figure 31.

The evolution of COF over time, for different loads and speeds, for two tests with the same parameters (F, v) [82].

## Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 32.

Since particle distribution is not even in contact during operation, this type of antiwear additive cannot help to improve tribological behavior because it does not reduce the friction coefficient and does not reduce the WSD as compared to those produce with neat soybean oil. The authors believe that the additive should be

From Figure 29, it is noticed that the wear pattern did not increase too much with the speed, but the quality of the surface has considerably worsened, which

The wear rate of wear scar diameter, w(WSD), helps to determine the influence of the concentration of this nanoadditive. In graphs in Figure 30, the neat oil is not given. The additive, either with 0.25% or 1%, makes the wear parameter to visibly decrease with speed only for low load (F = 100N). Comparison with nonadditivated soybean oil is highlighted on the maps in Figure 39, where 0% additive concentration is for the neat oil. It can be noted a decrease of w(WSD) with load for all concentrations and speeds, for the additivated lubricants; the slope of the speed dependence for the same load is lower. At v = 0.38 m/s, the influence of the additive concentration is insignificant and the additivation would be justified in the field of

For nanocarbon additivated lubricants, w(WSD) is less sensitive to additive concentration, especially for F = 300 N. The nonadditivated soybean oil can be recommended for light regimes (equivalent to F = 100–200 N and speed v = 0.38– 0.69 m/s). The almost linear dependence of WSD on the concentration of this additive is only observed for combinations with F = 100 N. For the tested regimes

Figure 31 shows the evolution over time of COF for all tests performed with soybean oil additivated with nanographite. There is a narrowing of its evolution range for v = 0.69 m/s for all loads and a scattering of higher COF values for low

Analyzing Figure 32, it can be noticed that, at F = 100 N (first horizontal line), the nanoadditive does not dramatically alter COF average. At high load (F = 300 N), COF increased for all additivated soybean oils as compared to the neat oil. The explanation would be that the graphite does not cover the entire surface of the contact but is only present in contact in the form of nanorolls, the reduced friction being zonal. There are also direct friction areas and friction areas with the third body (where nanoparticles or microparticles generated by agglomerating the first

The evolution of COF over time, for different loads and speeds, for two tests with the same parameters

(F = 100–300 N and v = 0.38–0.69 m/s), the results are not in the favor of

bonded (physically or chemically) for better results.

justifies the profilometry study in [41, 73].

Soybean - Biomass, Yield and Productivity

nanocarbon additivation of the soybean oil.

3.3.3 Soybean oil additivated with nanographite

high force for all speeds.

speeds and loads.

Figure 31.

(F, v) [82].

92

Average values and scattering intervals for two tests performed with the same parameters (F, v, c) [82, 83].

ones due to load and surface texture). It appears that the presence of graphite prevents the generation of EHL (elasto-hydrodinamic lubrication) film as COF has higher values, toward 0.1, especially for F = 300 N. No lower average COF values than those for the soybean oil have been obtained, except for tests: (F = 100 N, v = 0.38 m/s) and (F = 100 N, v = 0.53 m/s), with a graphite concentration of 0.25%wt. But the differences are too small to highlight an influence of the additive or the test regime. High values for wear rate of WSD at low load and speed imply more intense abrasion, which occurs if the lubricant film does not form and/or if the additive does not protect the contact. Maybe local particle agglomerations make the friction coefficient to oscillate and, when they migrate in contact, they allow one triboelement to fall over the other, in direct contact under higher load than if it had not encountered the graphite agglomerations.

Analyzing the photos in Figure 33, it can be noticed that the nature of the wear pattern does not change significantly, resulting from the abrasive wear process and with rare adhesive wear spots at higher loads.

Figure 33. Photos of the wear scars of the soybean oil +1% nanographite [82].

Comparing the graphs in Figure 34, they are similar in appearance, regardless of the concentration of the nanoadditive. The wear rate decreases with increasing load; for load F = 300 N, the wear rate of WSD is less influenced by speed.

3.3.4 Soybean oil additivated with graphene

DOI: http://dx.doi.org/10.5772/intechopen.81234

Tribological Behavior of Soybean Oil

fluid friction).

fluid film.

pointed out.

Figure 37.

Figure 38.

95

w(WSD) of soybean oil additivated with nanographene [41].

the nanoadditive in contact.

The evolution of COF over time is given in Figure 35, better ones being obtained for the highest concentration. COF variations have shortcuts or growth levels, which can be explained by the dynamics of COF components (dry friction, third body rubbing in areas with graphene nanoparticles, and partial

The addition of graphene does not improve COF but keeps it very close to the

values of neat soybean oil. At v = 0.38 m/s, the highest values were obtained irrespective of the concentration of the additive, suggesting that the improvement in friction (in the sense of reducing it) is due to the increase in speed (Figure 36) [41] and not on the additive, but the graphene does not prevent the formation of the

WSD does not significantly increase but the texture of the surface visibly changes (Figure 37), and the wear rate of WSD indicates a better tribological behavior of additivated soybean oil with graphene, but for more severe regimes (F = 200–300 N and v = 0.53–0.69 m/s), from this set of observations, the importance of correlation in the interpretation of several tribological parameters is

High values were obtained for the mildest test regime (F = 100 N, v = 0.38 m/s). One could argue that a low loaded contact does not keep the additive in contact (pressed and hung on the texture). The lowest value for the most severe regime (F = 300 N, v = 0.69 m/s) was explained by forming the EHD film and maintaining

Optical microscope photos of wear scar diameter, after testing with soybean oil +0.5% nanographene [41].

Figure 34. Wear rate of WSD for nanographite additivated lubricants [82].

Figure 35. The evolution of COF in time, depending on load and speed, for two tests with the same parameters (F, v) [41].

Figure 36.

Average values and spread range of friction coefficient (COF) for two tests performed with the same parameters (F, v, C) [41].

## 3.3.4 Soybean oil additivated with graphene

Comparing the graphs in Figure 34, they are similar in appearance, regardless of the concentration of the nanoadditive. The wear rate decreases with increasing load;

Average values and spread range of friction coefficient (COF) for two tests performed with the same parameters

The evolution of COF in time, depending on load and speed, for two tests with the same parameters (F, v) [41].

for load F = 300 N, the wear rate of WSD is less influenced by speed.

Wear rate of WSD for nanographite additivated lubricants [82].

Soybean - Biomass, Yield and Productivity

Figure 34.

Figure 35.

Figure 36.

94

(F, v, C) [41].

The evolution of COF over time is given in Figure 35, better ones being obtained for the highest concentration. COF variations have shortcuts or growth levels, which can be explained by the dynamics of COF components (dry friction, third body rubbing in areas with graphene nanoparticles, and partial fluid friction).

The addition of graphene does not improve COF but keeps it very close to the values of neat soybean oil. At v = 0.38 m/s, the highest values were obtained irrespective of the concentration of the additive, suggesting that the improvement in friction (in the sense of reducing it) is due to the increase in speed (Figure 36) [41] and not on the additive, but the graphene does not prevent the formation of the fluid film.

WSD does not significantly increase but the texture of the surface visibly changes (Figure 37), and the wear rate of WSD indicates a better tribological behavior of additivated soybean oil with graphene, but for more severe regimes (F = 200–300 N and v = 0.53–0.69 m/s), from this set of observations, the importance of correlation in the interpretation of several tribological parameters is pointed out.

High values were obtained for the mildest test regime (F = 100 N, v = 0.38 m/s). One could argue that a low loaded contact does not keep the additive in contact (pressed and hung on the texture). The lowest value for the most severe regime (F = 300 N, v = 0.69 m/s) was explained by forming the EHD film and maintaining the nanoadditive in contact.

Figure 37. Optical microscope photos of wear scar diameter, after testing with soybean oil +0.5% nanographene [41].

Figure 38.

w(WSD) of soybean oil additivated with nanographene [41].

The wear rate of WSD (Figure 38) is similar for 0.25 and 1%, meaning the additive concentration (0.25–1%) does not influence to much the wear. It seems that the wear is smaller for longer sliding distances and higher sliding speeds.

and c [%]), where F is the normal load on the four ball tribotester, v is the sliding

Friction coefficient and wear rate of wear scar diameter are important tribological characteristics, and they are compared in Figures 40 and 41 for neat soybean oil and the same oil additivated with nanocarbonic additives. COF has higher average values for soybean oil with graphite. This fact could be explained by local agglomerations of the nanosheets of graphite that migrate in contact, causing a mixt regime especially when the COF values overpass 0.1. Agglomeration of nanoparticles could also explain the balls. The high values in light regimes could be explained by the fact that the particles are not pressed

The downward trend of wear rate of wear scar diameter, w(WSD), had a higher gradient for lubricants with 1% nanoadditive (Figure 41), which would recommend further testing for more severe regimes, where additives are likely to better

Analyzing these tribological parameters, the authors consider that a combination (a low and constant evolution in time of friction coefficient, a small WSD, and a high value of FTP) makes the lubricant to have a good reliability in functioning. These laboratory test results have to be carefully applied when designing an actual applications with such a lubricants as in practice, the range of parameter variations is larger because of perturbations like vibrations, mechanical shocks, operator's

4. Conclusions and new trends in using soybean oil as lubricant

speed, and c is the mass concentration of nanoadditive.

enough to fill and remain on the surface texture).

errors, humidity, higher temperature gradients, etc.

Influence of additive in concentration of 1% on the friction coefficient [41].

Maps of the wear rate of WSD for lubricants additivated with 1% nanoadditive [41].

protect the surface of the contact.

Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

Figure 41.

97

Figure 40.

## 3.4 Maps for tribological parameters

The influence of the quality of the additive is manifested not only by the minimum value but also by the map area for which the minimum values of w(WSD) are spread (Figure 39). The lower surface of the map was noticed for graphene at 1% wt, between F = 200 N and F = 300 N and v = 0.69 m/s, less influenced by the amount of additive. For carbon, the low wear rate area is narrower. At v = 0.38 m/s and the lowest tested load, the lowest value of w(WSD) is obtained for graphite. The concentration of 1% nanoadditive enlarges the domain of reduced wear rate, meaning the load and speed have less influence on the test regime, especially for higher values for both parameters.

Maps were represented using a spline interpolation, and the surfaces are "compelled" to include the experimental data. A point on a wear rate map area is the wear rate of WSD for a test characterized by the set of input parameters (F [N], v [m/s],

Figure 39. Maps of w(WSD) for lubricants tested at two sliding speeds [41].

The wear rate of WSD (Figure 38) is similar for 0.25 and 1%, meaning the additive concentration (0.25–1%) does not influence to much the wear. It seems that the wear is smaller for longer sliding distances and higher sliding speeds.

The influence of the quality of the additive is manifested not only by the minimum value but also by the map area for which the minimum values of w(WSD) are spread (Figure 39). The lower surface of the map was noticed for graphene at 1% wt, between F = 200 N and F = 300 N and v = 0.69 m/s, less influenced by the amount of additive. For carbon, the low wear rate area is narrower. At v = 0.38 m/s and the lowest tested load, the lowest value of w(WSD) is obtained for graphite. The concentration of 1% nanoadditive enlarges the domain of reduced wear rate, meaning the load and speed have less influence on the test regime, especially for

Maps were represented using a spline interpolation, and the surfaces are "compelled" to include the experimental data. A point on a wear rate map area is the wear rate of WSD for a test characterized by the set of input parameters (F [N], v [m/s],

3.4 Maps for tribological parameters

Soybean - Biomass, Yield and Productivity

higher values for both parameters.

Figure 39.

96

Maps of w(WSD) for lubricants tested at two sliding speeds [41].

and c [%]), where F is the normal load on the four ball tribotester, v is the sliding speed, and c is the mass concentration of nanoadditive.

## 4. Conclusions and new trends in using soybean oil as lubricant

Friction coefficient and wear rate of wear scar diameter are important tribological characteristics, and they are compared in Figures 40 and 41 for neat soybean oil and the same oil additivated with nanocarbonic additives. COF has higher average values for soybean oil with graphite. This fact could be explained by local agglomerations of the nanosheets of graphite that migrate in contact, causing a mixt regime especially when the COF values overpass 0.1. Agglomeration of nanoparticles could also explain the balls. The high values in light regimes could be explained by the fact that the particles are not pressed enough to fill and remain on the surface texture).

The downward trend of wear rate of wear scar diameter, w(WSD), had a higher gradient for lubricants with 1% nanoadditive (Figure 41), which would recommend further testing for more severe regimes, where additives are likely to better protect the surface of the contact.

Analyzing these tribological parameters, the authors consider that a combination (a low and constant evolution in time of friction coefficient, a small WSD, and a high value of FTP) makes the lubricant to have a good reliability in functioning. These laboratory test results have to be carefully applied when designing an actual applications with such a lubricants as in practice, the range of parameter variations is larger because of perturbations like vibrations, mechanical shocks, operator's errors, humidity, higher temperature gradients, etc.

Figure 40. Influence of additive in concentration of 1% on the friction coefficient [41].

Figure 41.

Maps of the wear rate of WSD for lubricants additivated with 1% nanoadditive [41].

Soybean - Biomass, Yield and Productivity

## Author details

Constantin Georgescu<sup>1</sup> , Lorena Deleanu<sup>1</sup> \* and George Catalin Cristea<sup>2</sup>

1 Department of Mechanical Engineering, Faculty of Engineering, "Dunarea de Jos", University of Galati, Romania

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agrobiobase.com/en/

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Tribological Behavior of Soybean Oil

DOI: http://dx.doi.org/10.5772/intechopen.81234

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[8] Adhvaryu A, Erhan SZ. Epoxidized soybean oil as a potential source of hightemperature lubricants. Industrial Crops and Products. 2002;15:247-254. DOI: 10.1016/S0926-6690(01)00120-0

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s11746-006-1174-2

AMM.538.19

2017.05.022

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[Accessed: 2018-02-21]

2 National Institute for Aerospace Research "Elie Carafoli"—INCAS, Bucharest, Romania

\*Address all correspondence to: lorena.deleanu@ugal.ro

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

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[6] Ibrahim A, Ishak SSM, Kamaruddin MF. Comparison between sunflower oil and soybean oil as gear lubricant. Applied Mechanics and Materials. 2015; 699:443-448. DOI: 10.4028/www. scientific.net/AMM.699.443

[7] Peng D-X. Room temperature tribological performance of biodiesel (soybean oil). Industrial Lubrication and Tribology. 2016;68(6):617-623. DOI: 10.1108/ILT-10-2015-0143

[8] Adhvaryu A, Erhan SZ. Epoxidized soybean oil as a potential source of hightemperature lubricants. Industrial Crops and Products. 2002;15:247-254. DOI: 10.1016/S0926-6690(01)00120-0

[9] Castro W, Perez JM, Erhan SZ, Caputo F. A Study of the oxidation and wear properties of vegetable oils: soybean oil without additives. Journal of the American Oil Chemists' Society. 2006;83:47-52. DOI: 10.1007/ s11746-006-1174-2

[10] Fang JH, Xia DY, Chen BS, Wu J, Wang J. Friction and wear performances of magnesium alloy against steel under lubrication of soybean oil with scontaining additive. Applied Mechanics and Materials. 2014;538:19-23. DOI: 10.4028/www.scientific.net/ AMM.538.19

[11] Consumption of vegetable oils worldwide from 2013/14 to 2017/2018, by oil type [Internet]. 2017. Available from: https://www.statista.com/ statistics/263937/vegetable-oils-globalconsumption/ [Accessed: 2018-04-11]

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[13] Biresaw G, Bantchev G. Effect of chemical structure on film-forming properties of seed oils. Journal of Synthetic Lubrication. 2008;25:159-183. DOI: 10.1002/jsl.58

Author details

Romania

98

Constantin Georgescu<sup>1</sup>

Jos", University of Galati, Romania

Soybean - Biomass, Yield and Productivity

provided the original work is properly cited.

, Lorena Deleanu<sup>1</sup>

\*Address all correspondence to: lorena.deleanu@ugal.ro

1 Department of Mechanical Engineering, Faculty of Engineering, "Dunarea de

2 National Institute for Aerospace Research "Elie Carafoli"—INCAS, Bucharest,

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\* and George Catalin Cristea<sup>2</sup>

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indcrop.2014.01.030

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[16] Erhan SZ. Industrial Uses of Vegetable Oils. Peoria: AOCS Press; 2005. 184 p. ISBN: 1-893997-84-7

Boca Raton: CRC Press; 2006. pp. 353-360. ISBN: 1-57444-723-8

[18] Luna FMT, Rocha BS, Rola JEM, Albuquerque MCG, Azevedo DCS, Cavalcante JCL. Assessment of

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Environmentally adapted lubricants in Swedish forest industry: A critical review and case study. Industrial Lubrication and Tribology. 2000;52(3):

de Chimie. 2018;69(3):668-673

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116-125. DOI: 10.1108/ 00368790010326438

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[48] Fessenbecker A, Roehrs I, Pegnoglou R. Additives for environmentally acceptable lubricants. NLGI Spokesman. 1996;60(6):9-25

[49] Shahnazar S, Bagheri S, Hamid SBA. Enhancing lubricant properties by nano particle additives. International Journal of Hydrogen Energy. 2016;41:3153-3170. DOI: 10.1016/j.ijhydene.2015.12.040

[50] Zainal NA, Zulkifli NWM, Gulzar M, Masjuki HH. A review on the chemistry, production, and technological potential of bio-based lubricants. Renewable and Sustainable Energy Reviews. 2018;82:80-102. DOI: 10.1016/j.rser.2017.09.004

[51] Wu YY, Tsui WC, Liu TC. Experimental analysis of tribological properties of lubricating oils with nanoparticle additives. Wear. 2007;262: 819-825. DOI: 10.1016/j. wear.2006.08.021

[52] Wu H, Zhao J, Xia W, Cheng X, He A, Yun JH, et al. A study of the tribological behaviour of TiO2 nanoadditive water-based lubricants. Tribology International. 2017;109: 398-408. DOI: 10.1016/j. triboint.2017.01.013

[53] Wo H, Hu K, Hu XG. Tribological properties of MoS2 nanoparticles as additive in a machine oil. Tribology. 2004;24:33-37

[61] Lee K, Hwang Y, Cheong S, Choi Y, Kwon L, Lee J, et al. Understanding the

DOI: http://dx.doi.org/10.5772/intechopen.81234

different normal loads. Journal of Zhejiang University - Science A

13:633-640. DOI: 10.1631/jzus.

[69] Spanu C, Ripa M, Stefanescu I, Deleanu L. A comparation of

standardized methods for lubrication failure determination. The Annals of "Dunarea de Jos" University of Galati, Fascicle VIII, Tribology. 2007;XIII:

[70] Holmberg K. Quality of reporting empirical results in tribology [Internet]. 2005. Available from: http://virtual.vtt. fi/virtual/proj3/irg/docs/quality\_of\_ reporting\_kh190805 \_020905.doc

[71] Blok H. The flash temperature concept. Wear. 1963;6:483-494. DOI: 10.1016/0043-1648(63)90283-7

[72] Marscher WD. A critical evaluation of the Flash-Temperature concept. Journal ASLE Transactions. 1982;25:

[73] Deleanu L, Cristea GC, Georgescu C, Suciu C. Texture investigation of scars resulted from lubrication with

nanographite. In: Proceedings of the 2nd International Conference on Tribology (TURKEYTRIB'18), 18–20 April 2018,

[74] Georgescu C, Cristea CG, Dima S, Deleanu L. Evaluating lubricating capacity of vegetal oils using Abbott-Firestone curve. IOP Conference Series: Materials Science and Engineering. 2017;174:012057. DOI: 10.1088/ 1757-899X/174/1/012057

[75] Georgescu C. Use of vegetable oils to

[postdoctoral report]. Galati: Dunarea de Jos University of Galati; 2015

obtain ecological lubricants

[Accessed: 2018-05-12]

157-174. DOI: 10.1080/ 05698198208983077

soybean oil additivated with

Istanbul, Turkey

A1200021

99-103

(Applied Physics & Engineering). 2012;

[62] Tevet O, von-Huth P, Popovitz-Biro R, Rosentsveig R, Wagner HD, Tenne R. Friction mechanism of individual multilayered nanoparticles. Proceedings of the National Academy of Sciences of United States of America. 2011;108:

role of nanoparticles in nano-oil lubrication. Tribology Letters. 2009;35: 127-131. DOI: 10.1007/s11249-009-

Tribological Behavior of Soybean Oil

19901-19906. DOI: 10.1073/

350-354. DOI: 10.1016/j. triboint.2005.09.021

Coupling experimental and

2012;23:375701. DOI: 10.1088/ 0957-4484/23/37/375701

Springer Handbook of Materials

ISBN: 9783540303008

(European conditions)

103

[63] Akbulut M. Nanoparticle-based lubrication systems. Journal of Powder Metallurgy and Mining. 2012;1:e101. DOI: 10.4172/2168-9806.1000e101

[64] Jayadas NH, Nair KP, Ajithkumar G. Tribological evaluation of coconut oil as an environment-friendly lubricant. Tribology International. 2007;40:

[65] Lahouij I, Bucholz EW, Vacher B, Sinnott SB, Martin JM, Dassenoy F. Lubrication mechanisms of hollow-core inorganic fullerene-like nanoparticles:

computational works. Nanotechnology.

[66] Czichos H, Saito T, Smith L, editors.

Measurement Methods. Berlin: Springer Science-Business Media; 2006. 1208 p.

[67] EN ISO 20623:2017. Petroleum and related products. Determination of the extreme-pressure and anti-wear properties of fluids. Four ball method

[68] Tiong CI, Azli Y, Kadir MRA, Syahrullail S. Tribological evaluation of refined, bleached and deodorized palm stearin using four-ball tribotester with

pnas.1106553108

9441-7

[54] Wu JF, Zhai WS, Jie GF. Preparation and tribological properties of WS2 nanoparticles modified by trioctylamine. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology. 2009;223:695-703. DOI: 10.1243/ 13506501JET494

[55] Chinas-Castillo F, Spikes HA. Mechanism of action of colloidal solid dispersions. Journal of Tribology. 2003; 125:552-557. DOI: 10.1115/1.1537752

[56] Alves SM, Barros BS, Trajano MF, Ribeiro KSB, Moura E. Tribological behavior of vegetable oil-based lubricants with nanoparticles of oxides in boundary lubrication conditions. Tribology International. 2013;65:28-36. DOI: 10.1016/j.triboint.2013.03.027

[57] Gu C, Zhu G, Li L, Tian X, Zhu G. Tribological effects of oxide based nanoparticles in lubricating oils. Journal of Marine Science and Applications. 2009;8:71-76. DOI: 10.1007/ s11804-009-8008-1

[58] Iliuc I. Tribology of thin layers. 1st ed. New York: North Holland; 1980. 224 p. ISBN: 0-444-99768-7

[59] Yu H, Xu Y, Shi P, B-s X, Wang X, Liu Q. Tribological properties and lubricating mechanisms of Cu nanoparticles in lubricant. Transactions of Nonferrous Metals Society of China. 2008;18:636-641. DOI: 10.1016/ S1003-6326(08)60111-9

[60] Liu G, Li X, Qin B, Xing D, Guo Y, Fan R. Investigation of the mending effect and mechanism of copper nanoparticles on a tribologically stressed surface. Tribology Letters. 2004;17: 961-966. DOI: 10.1007/s11249-004- 8109-6

Tribological Behavior of Soybean Oil DOI: http://dx.doi.org/10.5772/intechopen.81234

[61] Lee K, Hwang Y, Cheong S, Choi Y, Kwon L, Lee J, et al. Understanding the role of nanoparticles in nano-oil lubrication. Tribology Letters. 2009;35: 127-131. DOI: 10.1007/s11249-009- 9441-7

viscosity modifiers. Tribology International. 2014;69:110-117. DOI: 10.1016/j.triboint.2013.08.016

Tribology of polymeric

978-0-444-53155-1

Romania: Iasi; 2018

[48] Fessenbecker A, Roehrs I, Pegnoglou R. Additives for

environmentally acceptable lubricants. NLGI Spokesman. 1996;60(6):9-25

[49] Shahnazar S, Bagheri S, Hamid SBA. Enhancing lubricant properties by nano particle additives. International Journal of Hydrogen Energy. 2016;41:3153-3170. DOI: 10.1016/j.ijhydene.2015.12.040

[50] Zainal NA, Zulkifli NWM, Gulzar M, Masjuki HH. A review on the chemistry, production, and

technological potential of bio-based lubricants. Renewable and Sustainable Energy Reviews. 2018;82:80-102. DOI:

10.1016/j.rser.2017.09.004

819-825. DOI: 10.1016/j. wear.2006.08.021

398-408. DOI: 10.1016/j. triboint.2017.01.013

102

[51] Wu YY, Tsui WC, Liu TC. Experimental analysis of tribological properties of lubricating oils with nanoparticle additives. Wear. 2007;262:

[52] Wu H, Zhao J, Xia W, Cheng X, He

A, Yun JH, et al. A study of the tribological behaviour of TiO2 nanoadditive water-based lubricants. Tribology International. 2017;109:

[46] Friedrich K, Schlarb AK, editors.

Soybean - Biomass, Yield and Productivity

[53] Wo H, Hu K, Hu XG. Tribological properties of MoS2 nanoparticles as additive in a machine oil. Tribology.

[54] Wu JF, Zhai WS, Jie GF. Preparation and tribological properties of WS2

2004;24:33-37

13506501JET494

nanoparticles modified by trioctylamine. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology. 2009;223:695-703. DOI: 10.1243/

[55] Chinas-Castillo F, Spikes HA. Mechanism of action of colloidal solid dispersions. Journal of Tribology. 2003; 125:552-557. DOI: 10.1115/1.1537752

[56] Alves SM, Barros BS, Trajano MF, Ribeiro KSB, Moura E. Tribological behavior of vegetable oil-based

lubricants with nanoparticles of oxides in boundary lubrication conditions. Tribology International. 2013;65:28-36. DOI: 10.1016/j.triboint.2013.03.027

[57] Gu C, Zhu G, Li L, Tian X, Zhu G. Tribological effects of oxide based nanoparticles in lubricating oils. Journal of Marine Science and Applications.

[58] Iliuc I. Tribology of thin layers. 1st ed. New York: North Holland; 1980. 224

[59] Yu H, Xu Y, Shi P, B-s X, Wang X, Liu Q. Tribological properties and lubricating mechanisms of Cu

nanoparticles in lubricant. Transactions of Nonferrous Metals Society of China. 2008;18:636-641. DOI: 10.1016/

[60] Liu G, Li X, Qin B, Xing D, Guo Y, Fan R. Investigation of the mending effect and mechanism of copper nanoparticles on a tribologically stressed surface. Tribology Letters. 2004;17: 961-966. DOI: 10.1007/s11249-004-

2009;8:71-76. DOI: 10.1007/

s11804-009-8008-1

p. ISBN: 0-444-99768-7

S1003-6326(08)60111-9

8109-6

nanocomposites–Friction and wear of bulk materials and coatings. 1st ed. Oxford: Elsevier; 2008. 568 p. ISBN:

[47] Cristea GC, Cazamir D, Dima D, Georgescu C, Deleanu L. Influence of TiO2 as nano additive in rapeseed oil. In: Proceedings of the 8th International Conference on Advanced Concepts in Mechanical Engineering (ACME).

[62] Tevet O, von-Huth P, Popovitz-Biro R, Rosentsveig R, Wagner HD, Tenne R. Friction mechanism of individual multilayered nanoparticles. Proceedings of the National Academy of Sciences of United States of America. 2011;108: 19901-19906. DOI: 10.1073/ pnas.1106553108

[63] Akbulut M. Nanoparticle-based lubrication systems. Journal of Powder Metallurgy and Mining. 2012;1:e101. DOI: 10.4172/2168-9806.1000e101

[64] Jayadas NH, Nair KP, Ajithkumar G. Tribological evaluation of coconut oil as an environment-friendly lubricant. Tribology International. 2007;40: 350-354. DOI: 10.1016/j. triboint.2005.09.021

[65] Lahouij I, Bucholz EW, Vacher B, Sinnott SB, Martin JM, Dassenoy F. Lubrication mechanisms of hollow-core inorganic fullerene-like nanoparticles: Coupling experimental and computational works. Nanotechnology. 2012;23:375701. DOI: 10.1088/ 0957-4484/23/37/375701

[66] Czichos H, Saito T, Smith L, editors. Springer Handbook of Materials Measurement Methods. Berlin: Springer Science-Business Media; 2006. 1208 p. ISBN: 9783540303008

[67] EN ISO 20623:2017. Petroleum and related products. Determination of the extreme-pressure and anti-wear properties of fluids. Four ball method (European conditions)

[68] Tiong CI, Azli Y, Kadir MRA, Syahrullail S. Tribological evaluation of refined, bleached and deodorized palm stearin using four-ball tribotester with

different normal loads. Journal of Zhejiang University - Science A (Applied Physics & Engineering). 2012; 13:633-640. DOI: 10.1631/jzus. A1200021

[69] Spanu C, Ripa M, Stefanescu I, Deleanu L. A comparation of standardized methods for lubrication failure determination. The Annals of "Dunarea de Jos" University of Galati, Fascicle VIII, Tribology. 2007;XIII: 99-103

[70] Holmberg K. Quality of reporting empirical results in tribology [Internet]. 2005. Available from: http://virtual.vtt. fi/virtual/proj3/irg/docs/quality\_of\_ reporting\_kh190805 \_020905.doc [Accessed: 2018-05-12]

[71] Blok H. The flash temperature concept. Wear. 1963;6:483-494. DOI: 10.1016/0043-1648(63)90283-7

[72] Marscher WD. A critical evaluation of the Flash-Temperature concept. Journal ASLE Transactions. 1982;25: 157-174. DOI: 10.1080/ 05698198208983077

[73] Deleanu L, Cristea GC, Georgescu C, Suciu C. Texture investigation of scars resulted from lubrication with soybean oil additivated with nanographite. In: Proceedings of the 2nd International Conference on Tribology (TURKEYTRIB'18), 18–20 April 2018, Istanbul, Turkey

[74] Georgescu C, Cristea CG, Dima S, Deleanu L. Evaluating lubricating capacity of vegetal oils using Abbott-Firestone curve. IOP Conference Series: Materials Science and Engineering. 2017;174:012057. DOI: 10.1088/ 1757-899X/174/1/012057

[75] Georgescu C. Use of vegetable oils to obtain ecological lubricants [postdoctoral report]. Galati: Dunarea de Jos University of Galati; 2015

[76] Nanomaterials and related products [Internet]. 2016. Available from: http:// www.plasmachem.com/ download/PlasmaChem-General\_ Catalogue\_Nanomaterials.pdf [Accessed: 2018-05-12]

Chapter 6

Abstract

506,500 seeds ha<sup>1</sup>

1. Introduction

row spacing or wider [1].

105

Row Spacing and Seeding Rate

Effects on Soybean Seed Yield

Soybean growers in the northern latitudes of the United States plant the crop in a

), and two soybean varieties at each location. Soybean had

wide range of row spacings although there has been a shift toward wider rows (>50 cm) in some Upper Midwest states in the last 5 years. The objective of this study was to evaluate the impact of row spacing and seeding rate on the performance of soybean and to determine whether these management practices interact to influence soybean yield. A row spacing study was conducted at Aberdeen and Beresford, South Dakota, USA, in 2014 and 2015. The study had two row spacings

greater stand establishment in 19 cm rows (6–10% higher) compared with 76 cm rows. Soybean in 19 cm rows yielded 0.8–10% more than in 76 cm rows depending on the location or year. Seed yield increased with increasing seeding rate with the highest seeding rate of 506,000 seeds ha<sup>1</sup> yielding greatest. The increase in seed yield due to the increase in seeding rate ranged from 3 to 7%. At each location, the longer duration soybean variety yielded higher than the shorter duration variety.

Soybean (Glycine max) is the second most planted crop after corn worldwide and is the second most important source of crop revenue in South Dakota [1]. Research conducted in the Upper Midwest of the United States documents a con-

narrow row spacings (<50 cm) when compared to those grown at wider row spacings (50–76 cm) [2–4]. Another research, however, showed no yield advantage to narrow row spacing [5]. Cox and Cherney [6] reported that soybean drilled in 19 cm rows yielded 7% more than soybeans planted with a row crop planter in 38 cm rows and 17% more than soybean planted in 76 cm rows in Northeastern United States. Even with these reports of yield advantage or no yield difference, 69% of soybean growers in South Dakota, 54% in Nebraska, and 49% in Iowa grow soybean in 76 cm

Lee [7] reported that in Central and Southern United States row spacing studies

usually found no increase in yield in narrow rows over wider rows. This was confirmed by Thompson et al. [8] who reported that yield responses to narrow row spacing in the Mid-South United States were inconsistent and mainly influenced by weather. The increase in yield from narrow row spacings in the Northern United

, for soybean grown in

(19 and 76 cm), four seeding rates (247,000, 333,500, 420,000, and

Keywords: soybean, Glycine max, row spacing, seeding rate, seed yield

sistent yield advantage, in the range of 134–604 kg ha<sup>1</sup>

Matthew Schutte and Thandiwe Nleya

[77] Cameron A. Basic Lubrication Theory. 3rd ed. Chichester: Ellis Horwood Ltd.; 1983. 256 p. ISBN: 978-0470275542

[78] Cheenkachorn K. A study of wear properties of different soybean oils. Energy Procedia. 2013;42:633-639. DOI: 10.1016/j.egypro.2013.11.065

[79] Zhao X, Yang J, Tao D, Xu X. Tribological study of nitrogen plasma polymerized soybean oil with nitrogen heterocyclic structures. Industrial Crops and Products. 2013;51:236-243. DOI: 10.1016/j.indcrop.2013.08.074

[80] Battez AH, Rico JEF, Arias AN, Rodriguez JLV, Rodriguez RC, Fernandez JMD. The tribological behaviour of ZnO nanoparticles as an additive to PAO6. Wear. 2006;261: 256-263. DOI: 10.1016/j. wear.2005.10.001

[81] Zulkifli NWM, Kalam MA, Masjuki HH, Yunus R. Experimental analysis of tribological properties of biolubricant with nanoparticle additive. Procedia Engineering. 2013;68:152-157. DOI: 10.1016/j.proeng.2013.12.161

[82] Cristea GC, Dima C, Georgescu C, Dima D, Deleanu L, Solea LC. Evaluating lubrication capability of soybean oil with nano carbon additive. Tribology in Industry. 2018;40(1): 66-72. DOI: 10.24874/ti.2018.40.01.05

[83] Cristea GC, Dima C, Dima D, Georgescu C, Deleanu L. Nano graphite as additive in soybean oil. MATEC Web of Conferences. 2017;112:04023. DOI: 10.1051/matecconf/201711204023

## Chapter 6

[76] Nanomaterials and related products [Internet]. 2016. Available from: http://

Soybean - Biomass, Yield and Productivity

download/PlasmaChem-General\_ Catalogue\_Nanomaterials.pdf [Accessed: 2018-05-12]

[77] Cameron A. Basic Lubrication Theory. 3rd ed. Chichester: Ellis Horwood Ltd.; 1983. 256 p. ISBN:

[78] Cheenkachorn K. A study of wear properties of different soybean oils. Energy Procedia. 2013;42:633-639. DOI:

10.1016/j.egypro.2013.11.065

[79] Zhao X, Yang J, Tao D, Xu X. Tribological study of nitrogen plasma polymerized soybean oil with nitrogen heterocyclic structures. Industrial Crops and Products. 2013;51:236-243. DOI: 10.1016/j.indcrop.2013.08.074

[80] Battez AH, Rico JEF, Arias AN, Rodriguez JLV, Rodriguez RC, Fernandez JMD. The tribological behaviour of ZnO nanoparticles as an additive to PAO6. Wear. 2006;261:

[81] Zulkifli NWM, Kalam MA, Masjuki HH, Yunus R. Experimental analysis of tribological properties of biolubricant with nanoparticle additive. Procedia Engineering. 2013;68:152-157. DOI: 10.1016/j.proeng.2013.12.161

[82] Cristea GC, Dima C, Georgescu C,

Dima D, Deleanu L, Solea LC. Evaluating lubrication capability of soybean oil with nano carbon additive. Tribology in Industry. 2018;40(1): 66-72. DOI: 10.24874/ti.2018.40.01.05

[83] Cristea GC, Dima C, Dima D, Georgescu C, Deleanu L. Nano graphite as additive in soybean oil. MATEC Web of Conferences. 2017;112:04023. DOI: 10.1051/matecconf/201711204023

104

256-263. DOI: 10.1016/j. wear.2005.10.001

www.plasmachem.com/

978-0470275542

## Row Spacing and Seeding Rate Effects on Soybean Seed Yield

Matthew Schutte and Thandiwe Nleya

## Abstract

Soybean growers in the northern latitudes of the United States plant the crop in a wide range of row spacings although there has been a shift toward wider rows (>50 cm) in some Upper Midwest states in the last 5 years. The objective of this study was to evaluate the impact of row spacing and seeding rate on the performance of soybean and to determine whether these management practices interact to influence soybean yield. A row spacing study was conducted at Aberdeen and Beresford, South Dakota, USA, in 2014 and 2015. The study had two row spacings (19 and 76 cm), four seeding rates (247,000, 333,500, 420,000, and 506,500 seeds ha<sup>1</sup> ), and two soybean varieties at each location. Soybean had greater stand establishment in 19 cm rows (6–10% higher) compared with 76 cm rows. Soybean in 19 cm rows yielded 0.8–10% more than in 76 cm rows depending on the location or year. Seed yield increased with increasing seeding rate with the highest seeding rate of 506,000 seeds ha<sup>1</sup> yielding greatest. The increase in seed yield due to the increase in seeding rate ranged from 3 to 7%. At each location, the longer duration soybean variety yielded higher than the shorter duration variety.

Keywords: soybean, Glycine max, row spacing, seeding rate, seed yield

## 1. Introduction

Soybean (Glycine max) is the second most planted crop after corn worldwide and is the second most important source of crop revenue in South Dakota [1]. Research conducted in the Upper Midwest of the United States documents a consistent yield advantage, in the range of 134–604 kg ha<sup>1</sup> , for soybean grown in narrow row spacings (<50 cm) when compared to those grown at wider row spacings (50–76 cm) [2–4]. Another research, however, showed no yield advantage to narrow row spacing [5]. Cox and Cherney [6] reported that soybean drilled in 19 cm rows yielded 7% more than soybeans planted with a row crop planter in 38 cm rows and 17% more than soybean planted in 76 cm rows in Northeastern United States. Even with these reports of yield advantage or no yield difference, 69% of soybean growers in South Dakota, 54% in Nebraska, and 49% in Iowa grow soybean in 76 cm row spacing or wider [1].

Lee [7] reported that in Central and Southern United States row spacing studies usually found no increase in yield in narrow rows over wider rows. This was confirmed by Thompson et al. [8] who reported that yield responses to narrow row spacing in the Mid-South United States were inconsistent and mainly influenced by weather. The increase in yield from narrow row spacings in the Northern United

States has been attributed to a shorter growing season meaning soybean has limited time to reach maximum radiation interception prior to flowering. Narrow rows therefore increase radiation interception during the critical periods for grain set resulting in earlier canopy closure and less light being usable for weeds if initial weed control is satisfactory [9–12]. Along with higher rate of light interception, less evapotranspiration was reported in narrow rows due to faster canopy closure and thus resulted in a higher water-use efficiency [13]. However, in years of drought stress, narrow rows can deplete soil water sooner by increased vegetative growth and result in insufficient soil water availability during reproductive stages and therefore no yield advantage over wider rows [2, 14].

2. Materials and methods

Row Spacing and Seeding Rate Effects on Soybean Seed Yield

DOI: http://dx.doi.org/10.5772/intechopen.80748

season are shown in Table 1.

Average monthly temperature (°C)

2018.

Table 1.

107

The study was conducted at two locations, Southeast Research Farm, Beresford, South Dakota (SD) (43.052548°N, 96.904135°W), and Aberdeen, SD (45.464698° N, 98.486483°W) in 2014 and 2015. At Beresford, the soil textural classification was Egan-Clarno-Chancellor complex, fine silty, and fine loam [27]. At Aberdeen, the soil textural classification was Great Bend fine silty, mixed, superactive, and frigid calcic Hapludolls [28]. The experimental fields were plowed in the fall and cultivated twice in the spring before planting soybean. The soybean was grown under dryland conditions. The total rainfall and mean air temperature for each growing

The experimental design was a randomized complete block in a split-plot arrangement, with four replications. The main plots were two row spacings. Subplot treatments were four seeding rates of 247,000, 333,500, 420,000, and 506,500 viable seeds ha<sup>1</sup> and two soybean varieties arranged in a factorial design. The two row spacings were 19 and 76 cm rows. The soybean varieties were different at each location based on maturity grouping ideal for the area and were also slightly different in resistance to white mold. At the Aberdeen location, the varieties were 0906R2 and 1108R2 and at Beresford were 2306R2 and 2408R2 (Channel, St. Louis, MO). At each specific location, varieties 0906R2 and 2306R2 were of shorter duration than 1108R2 and 2408R2. The rating for white mold were 3 for 0906R2, 4 for 1108R2, 3 for 2306R2, and 6 for 2408R2 on a scale of 1–9 (1 resistant and 9 susceptible) [29]. In 2014, the planting dates were June 9 and May 28 at Aberdeen and Beresford, respectively. In 2015, the planting dates were June 9 at Aberdeen and June 10 at Beresford. For the 76 cm row spacing, soybean was planted in four rows that was 6.4 m long and trimmed back to 5.5 m when they reached the V3 stage. The center

Location Year May June July August September October Average Aberdeen 2014 12.89 17.53 19.61 19.58 15.33 9.14 15.68 Aberdeen 2015 12.94 20.56 22.58 20.42 18.39 10.44 17.56 30-year average 13.55 18.65 21.80 20.56 14.95 7.29 16.1 Beresford 2014 15.31 20.19 20.50 21.14 16.47 10.31 17.32 Beresford 2015 14.58 20.83 22.14 20.22 19.61 11.42 18.13 30-year average 15.03 20.53 22.81 21.56 16.58 9.41 16.2 Monthly rainfall (mm) Total Aberdeen 2014 55.37 84.07 17.78 157.23 25.40 6.60 346.46 Aberdeen 2015 162.31 53.34 103.12 74.68 9.40 41.66 444.50 30-year average 78.99 93.98 75.95 61.72 55.63 50.55 416.60 Beresford 2014 62.99 342.90 27.18 75.18 61.47 34.54 604.27 Beresford 2015 89.66 90.42 150.11 179.07 92.46 26.42 628.14 30-year average 92.46 110.74 83.31 72.39 74.42 54.61 487.90 Source: High Plains Regional Climate Center, University of Nebraska, http://xmacis.rcc-acis.org/#, last accessed 6/13/

Monthly average air temperature and rainfall at Aberdeen and Beresford, SD, for 2014 and 2015.

Some studies have reported row spacing seeding rate interactions with soybean yielding greater with higher seeding rates and narrow rows when compared to wide rows [3, 6, 15, 16]. Cox et al. [3] reported a greater profit of US\$30 ha<sup>1</sup> with a seeding rate of 420,000 seeds ha<sup>1</sup> in 19 cm rows compared to 321,000 seeds ha<sup>1</sup> in 76 cm rows due to yield increase outweighing seed costs. Other studies have reported similar optimum seeding rates between narrow and wide rows and therefore no interaction between row spacing and seeding rate [17–19]. Ricks et al. [20] reported that the optimum seeding rates for South Dakota typically range between 355,000 seeds ha<sup>1</sup> and 381,000 seeds ha<sup>1</sup> . However, they also reported that higher yields have been reported with seeding rates greater than 406,000 seeds ha<sup>1</sup> .

Carpenter and Board [21] reported that soybean plants compensate for space in the canopy by adding branches, and they found no yield response to increased seeding rates. This was supported by Cox and Cherney [6] who found that not only did soybean plants compensate with biomass, pods, and seeds per plant at lower seeding rates but also found that soybean compensated for wider rows (>38 cm) as well. They also found that though soybean plants do compensate for both lower seeding rates and wider rows, they were less efficient at compensating for wider rows than for lower seeding rates, meaning that row spacing had a greater effect on yield than seeding rate. Wiatrak and Chen [22] found that increasing seeding rate may improve soybean growth at early vegetative stages, which in turn can result in increase in yield. However, they found that seeding rates above 272,000 seeds ha<sup>1</sup> did not follow this trend and did not increase vegetative growth.

White mold (also called Sclerotinia stem rot), a disease caused by the fungus Sclerotinia sclerotiorum, is a yield-limiting soybean disease in North Central United States. Management practices such as narrow row spacing, increased plant populations, early planting dates, and high-soil fertility can increase soybean yields but have the unintended consequence of increasing white mold development within the soybean canopy [23, 24]. While fungicides are available to control white mold, complete control of the disease using only chemical management is usually not possible [24]. Thus, in addition to fungicides, management strategies for controlling white mold in soybean include cultivars selection and management practices to reduce canopy density [24, 25]. Planting in wide row spacings or at lower plant populations delays canopy closer, reduces canopy density, and thus prevents favorable conditions for white mold development [24, 26].

With increase in soybean planted in wider rows (50–76 cm) in South Dakota and neighboring states in the Upper Midwest, there is a need to evaluate the value of this practice especially with recent research results suggesting that narrow rows have an advantage or at least yield the same as wider rows in the Upper Midwest. The objectives of this study were to (i) determine the effect of row spacing and seeding rate on soybean yield and (ii) measure the interactions between the two management practices.

## 2. Materials and methods

States has been attributed to a shorter growing season meaning soybean has limited time to reach maximum radiation interception prior to flowering. Narrow rows therefore increase radiation interception during the critical periods for grain set resulting in earlier canopy closure and less light being usable for weeds if initial weed control is satisfactory [9–12]. Along with higher rate of light interception, less evapotranspiration was reported in narrow rows due to faster canopy closure and thus resulted in a higher water-use efficiency [13]. However, in years of drought stress, narrow rows can deplete soil water sooner by increased vegetative growth and result in insufficient soil water availability during reproductive stages and

Some studies have reported row spacing seeding rate interactions with soybean yielding greater with higher seeding rates and narrow rows when compared to wide rows [3, 6, 15, 16]. Cox et al. [3] reported a greater profit of US\$30 ha<sup>1</sup> with a seeding rate of 420,000 seeds ha<sup>1</sup> in 19 cm rows compared to 321,000 seeds ha<sup>1</sup> in 76 cm rows due to yield increase outweighing seed costs. Other studies have reported similar optimum seeding rates between narrow and wide rows and therefore no interaction between row spacing and seeding rate [17–19]. Ricks et al. [20] reported that the optimum seeding rates for South Dakota typically range between

yields have been reported with seeding rates greater than 406,000 seeds ha<sup>1</sup>

the canopy by adding branches, and they found no yield response to increased seeding rates. This was supported by Cox and Cherney [6] who found that not only did soybean plants compensate with biomass, pods, and seeds per plant at lower seeding rates but also found that soybean compensated for wider rows (>38 cm) as well. They also found that though soybean plants do compensate for both lower seeding rates and wider rows, they were less efficient at compensating for wider rows than for lower seeding rates, meaning that row spacing had a greater effect on yield than seeding rate. Wiatrak and Chen [22] found that increasing seeding rate may improve soybean growth at early vegetative stages, which in turn can result in increase in yield. However, they found that seeding rates above 272,000 seeds ha<sup>1</sup>

did not follow this trend and did not increase vegetative growth.

able conditions for white mold development [24, 26].

management practices.

106

Carpenter and Board [21] reported that soybean plants compensate for space in

White mold (also called Sclerotinia stem rot), a disease caused by the fungus Sclerotinia sclerotiorum, is a yield-limiting soybean disease in North Central United

populations, early planting dates, and high-soil fertility can increase soybean yields but have the unintended consequence of increasing white mold development within the soybean canopy [23, 24]. While fungicides are available to control white mold, complete control of the disease using only chemical management is usually not possible [24]. Thus, in addition to fungicides, management strategies for controlling white mold in soybean include cultivars selection and management practices to reduce canopy density [24, 25]. Planting in wide row spacings or at lower plant populations delays canopy closer, reduces canopy density, and thus prevents favor-

With increase in soybean planted in wider rows (50–76 cm) in South Dakota and neighboring states in the Upper Midwest, there is a need to evaluate the value of this practice especially with recent research results suggesting that narrow rows have an advantage or at least yield the same as wider rows in the Upper Midwest. The objectives of this study were to (i) determine the effect of row spacing and seeding rate on soybean yield and (ii) measure the interactions between the two

States. Management practices such as narrow row spacing, increased plant

. However, they also reported that higher

.

therefore no yield advantage over wider rows [2, 14].

355,000 seeds ha<sup>1</sup> and 381,000 seeds ha<sup>1</sup>

Soybean - Biomass, Yield and Productivity

The study was conducted at two locations, Southeast Research Farm, Beresford, South Dakota (SD) (43.052548°N, 96.904135°W), and Aberdeen, SD (45.464698° N, 98.486483°W) in 2014 and 2015. At Beresford, the soil textural classification was Egan-Clarno-Chancellor complex, fine silty, and fine loam [27]. At Aberdeen, the soil textural classification was Great Bend fine silty, mixed, superactive, and frigid calcic Hapludolls [28]. The experimental fields were plowed in the fall and cultivated twice in the spring before planting soybean. The soybean was grown under dryland conditions. The total rainfall and mean air temperature for each growing season are shown in Table 1.

The experimental design was a randomized complete block in a split-plot arrangement, with four replications. The main plots were two row spacings. Subplot treatments were four seeding rates of 247,000, 333,500, 420,000, and 506,500 viable seeds ha<sup>1</sup> and two soybean varieties arranged in a factorial design. The two row spacings were 19 and 76 cm rows. The soybean varieties were different at each location based on maturity grouping ideal for the area and were also slightly different in resistance to white mold. At the Aberdeen location, the varieties were 0906R2 and 1108R2 and at Beresford were 2306R2 and 2408R2 (Channel, St. Louis, MO). At each specific location, varieties 0906R2 and 2306R2 were of shorter duration than 1108R2 and 2408R2. The rating for white mold were 3 for 0906R2, 4 for 1108R2, 3 for 2306R2, and 6 for 2408R2 on a scale of 1–9 (1 resistant and 9 susceptible) [29].

In 2014, the planting dates were June 9 and May 28 at Aberdeen and Beresford, respectively. In 2015, the planting dates were June 9 at Aberdeen and June 10 at Beresford. For the 76 cm row spacing, soybean was planted in four rows that was 6.4 m long and trimmed back to 5.5 m when they reached the V3 stage. The center


#### Table 1.

Monthly average air temperature and rainfall at Aberdeen and Beresford, SD, for 2014 and 2015.

two rows were harvested for yield data, while the outer two rows were buffers. For the 19 cm row spacing, soybean was planted in 16 rows that is 6.5 m long and trimmed back to 5.5 m at V3 stage. The eight center rows were harvested for yield data with eight buffer rows on either side. The data collected included the number of plants ha<sup>1</sup> at the V4 growth stage determined by counting the number of plants in the middle two rows for the 76 cm row spacing and eight rows for the 19 cm row spacing and converting to plants ha<sup>1</sup> . Seed yield was determined by harvesting two center rows (76 cm spacing) and eight center rows (19 cm spacing) with a smallplot combine (Massey Ferguson 8XP, Duluth, Georgia, USA). Seed subsamples from each plot were taken to determine moisture, protein, and oil content. Seed moisture was determined by weighing seed samples before drying at 60°C for 48 hours and reweighing the samples after drying to adjust seed moisture to 13% or 130 g kg<sup>1</sup> . Seed protein and seed oil were determined using a near-infrared transmittance (NIT) spectroscopy (Infratec 1229 Grain Analyzer, Foss Tecator AB).

Weeds were managed with a preemergent herbicide application of S-metolachlor (Dual II) (Bayer CropScience, Research Triangle Park, NC) and two in-season application of glyphosate (PowerMax) (Monsanto Company, St. Louis, MO). The insecticide Baythroid [cyano(4-fluoro-3-phenoxyphenyl)methyl-3- (2,2-dichloro-ethenyl)-2,2-dimethyl-cyclopropanecarboxylate] (Bayer CropScience, Research Triangle Park, NC) was applied when soybean aphids (Aphis glycines) reached economic thresholds.

Data were analyzed using PROC MIXED of SAS (SAS Research Institute, NC). Years and blocks were treated as random, and all other effects were considered fixed. Levene's test was used to test for the homogeneity of variance. After combined analysis revealed interactions between location and year, the data were split by year and then by location to analyze the significant interactions between row spacing, variety, and seeding rate within each location. Mean separation was performed using Fisher's protected LSD (0.05).

## 3. Results and discussion

### 3.1 Climate and weather

Average temperatures were slightly warmer at Beresford compared to Aberdeen, although in 2015, September was much warmer compared to 2014 at both locations (Table 1). Rainfall amounts and timing varied considerably for each location and each year. Aberdeen was drier (70.1 mm less rain) than long-term average in 2014 and wetter (28.1 mm more) than long-term average in 2015. Beresford was wetter than long-term average in both years with June 2014 receiving 132.1 mm more rain than average. The warmer and wetter conditions at Beresford in both years were conducive to overall better soybean growth and yield when compared to Aberdeen.

### 3.2 Established plant population

In 2014, the effects of row spacing on number of plants ha<sup>1</sup> and percent stand establishment (relative to seeding rate) were significant (<0.001) at both locations, while in 2015, row spacing effects were significant for the two traits (P = 0.02 and 0.01, respectively) only at Aberdeen (Table 2). Overall, plant establishment was greater in narrow rows compared with wide rows. On average, the difference in stand establishment between the two row spacings was greater at the Aberdeen location (10% points) compared to Beresford (6% points). Greater stand

2014

109

Aberdeen

Plants (ha1)

> Row spacing (S) (cm)

19 76

Seeding rate (RS) (seeds ha1

247,000 333,500 420,000 506,500 Variety (V)#

0906R2/2306R2 1108R2/2408R2

318,313b Analysis of variance

<0.001 <0.001 <0.001

0.048 0.748 0.524 0.758

<0.001 <0.001 <0.001

0.028 0.688 0.172 0.722

0.025 <0.001

0.316 0.811 0.539 0.992 0.451

0.009 <0.001

0.069 0.850 0.560 0.993 0.538

0.020 <0.001

0.036 0.141 0.086 0.424 0.946

0.016 0.091 0.604 0.091 0.062 0.166 0.928

0.079 0.243 0.181 0.631

0.075 <0.001 0.444

0.097

<0.001

0.521

0.053

0.232

0.197

0.512

S SR S SR

V V S

V SR V SR S \*Within each column and each treatment, means followed by the same letter are not significantly different (P 0.05).

#Soybean varieties 0906R2 and 1108R2 were grown at Aberdeen and 2306R2 and 2408R2 at Beresford.

Table 2. Established

 plant population

 and percentage

 (%) established

 plants (relative to seeding rate) at Aberdeen and Beresford locations, SD, in 2014 and 2015.

323,733a

87.1a 85.3b

301,981 300,374

80.9 80.7

302,467 310,203

80.5 82.2

306,690 317,678

82.3

85.6

230,821d 288,003c 345,634b 419,634a

93.4 a 86.3b 82.8c 82.2c

208,247d

281,575c 334,048b 380,840a

84.4a 84.3a 79.5b 75.2b

204,585d 276,940c 345,335b 398,480a

82.8 83.0 82.2 76.7

220,431d 290,395c 346,755b 391,155a

89.2a

Row Spacing and Seeding Rate Effects on Soybean Seed Yield

87.0ab

82.6b

77.2c

)

352,975a\* 279,071b

96.7a 75.7b

315,660a 286,695b

85.1a 76.6b

324,032a 288,638b

86.2a 77.1b

316,557 307,811

85.3

82.7

DOI: http://dx.doi.org/10.5772/intechopen.80748

 Percentage (%) stand

 Plants (ha1)

 Percentage (%) stand

 Plants (ha1)

 Percentage (%) stand

 Plant (ha1)

 Percentage (%) stand

Beresford

2015

Aberdeen

Beresford

