**3. Comparison between synthetic ESTER and B100 or FAME (fatty acid methyl Ester)**

#### **3.1 Synthetic Ester**

**Esters** are the result of the chemical reaction of an organic acid and an alcohol. Acid with two carboxyl groups (a functional group characteristic of organic acids) is called a diacid and the product of its reaction with alcohol is called diester. The alcohol that has more than one hydroxyl group (functional group characteristic of alcohols) is called a polyol. The product of the reaction of an organic acid with a polyol is called a polyol ester [13].

**Diester** These are mostly used among synthetic esters. They are more stable to oxidation and heat than hydrocarbons, beginning to decompose at 200°C. They contain two carboxyl, (C = 0) responsible for the characteristic of the polar substance (**Figure 2**).

#### **3.2 B100 or Fame (fatty acid methyl Ester)**

They contain three carboxyl (C = 0), responsible for the characteristic of the polar substance. These various adsorbed layers of biodiesel molecules (3 esters, 3(c = o)), constitute the key to the performance of B100 as a biolubricant, which allows it to withstand high pressures and high shear rate (HPHS), in any lubrication regimen and engine workload (**Figure 3**).

When machine surfaces interact with higher pressures and temperatures, additives mitigate the typical effects of metal-to-metal contact (wear) by creating initial molecular layers on the machine surface that are more ductile. These friction control layers directly reduce shear resistance during contact and are sacrificed.

The first layers can mitigate friction by allowing the weaker molecular bonds in the lubricant to be released with less force compared to the strong bonds that result from film boundary conditions due to metal-to-metal contact of surface asperities. The formation of low shear strength films is also affected by the type of base oil and the metallurgy of the surfaces.

There are three types of lubricant additives that help reduce this friction and control wear: friction modifiers, anti-wear additives, and extreme pressure additives [14].


**Figure 2.** *Diester: Two carbonyl.* *Bio-Circular Engine: Simultaneous and Successive Use of BioDiesel as Bio-Lubricant… DOI: http://dx.doi.org/10.5772/intechopen.103663*

#### **Figure 3.**

*Triester: (biodiesel). Transesterification process.*

In this tribological scenario, the main characteristic of B100 as biolubricant becomes important (B100 is Tri-Ester). This means that B100 has an adsorption intermolecular force 50% higher than commercial fossil synthetic ester bases (Di-Ester). This condition of intermolecular power superiority translates into a constant presence of the lubricant film, even in extreme lubrication conditions such as those mentioned here.

It is also important to highlight that most additives for motor oils, for the different functions required (detergents, dispersants, anti-wear, anti-rust, high pressure, etc.), are polar substances (eg. ZDDP); the vast majority are also based on sulfur, phosphorus, zinc, and others that are highly polluting the environment, in addition to triggering chemical processes that deteriorate the quality of the oils inside the engines.

#### *3.2.1 Fatty acid composition*

**Table 1** shows the composition of fatty acids, in the central column, it is shown in yellow, half corresponds to saturated fatty acids and the other half to unsaturated


#### **Table 1.**

*Fatty acid composition of palm oil.*

fatty acids. This represents the connection key that, from the concept of biofuel, brings us closer to the concepts of biolubricants.

The unsaturated compounds have an iodine value close to 85 g I/100 g of sample, while the saturated ones have an almost zero value. Unsaturated oils have a low viscosity and a lower pour point than their saturated counterparts.

Cold properties are strongly influenced by the degree of unsaturation; unsaturated compounds remain liquid at temperatures below 0°C, while saturated compounds are solid at room temperature. Saturated compounds have higher oxidative stability due to the absence of double bonds, but poor cold properties. Only unsaturated compounds are suitable for use as lubricants, but they can only be used under operating conditions that do not require high oxidative stability [15].

#### **3.3 Common characteristics**

Some characteristics between diesters (synthetics) and triester (B100). Diesters and triester have natural properties of lubricity and high detergency and dispersance, so they receive the name of clean operating lubricants. Their thermal stability allows them to work up to 180°C. They can operate at low temperatures since its freezing points are between –50 and –60°C (only some B100s). The viscosity index is high, close to 140. They have low volatility, high solvency for both additives and tanks, cleaning the sludge left previously; they tend to dissolve varnishes and lacquers. Soften the elastomers of the seals, therefore, it is recommended to use with these oils, viton seals and medium to high nitrile buna N. They are compatible with mineral oils and are biodegradable [12].
