Author details

In another study [45], a multi-function additive as detergent/dispersant/antioxidant/anti-wear was developed from L-histidine (HDS) for bio-lubricant applications. Two types additives namely, Ca-HDS-L and Ca-HDS-M were synthesized by esterification with lauroyl chloride and myristoyl chloride, respectively. Using the products in a polyol base oil indicated that Ca-HDS-L worked as a better detergent and dispersant, but Ca-HDS-M functioned as a more effective antioxidant. The oxidative properties obtained by the two additives (ca. 1–3 g/l

Lubricant TAN (soluble) Total sludge (%) Total oxidation products (%)

Polyol 2.019 32.454 34.416 Polyol +1000 ppm Ca-HDS-L 1.598 0.497 3.530 Polyol +2000 ppm Ca-HDS-L 1.514 0.022 1.300 Polyol +3000 ppm Ca-HDS-L 1.402 0.013 1.579 Polyol +1000 ppm Ca-HDS-M 0.476 0.065 2.423 Polyol +2000 ppm Ca-HDS-M 1.514 0.076 1.282 Polyol +3000 ppm Ca-HDS-M 1.458 0.021 1.183

Competent and creative research is still needed in the study of oil antioxidants. Some important questions as why one type of antioxidant is efficient in one kind of oil and inefficient in another is often puzzling. Lubricants can affect the environment to various extents; thus, the development of new environmentally friendly lubricant formulations is required. Moreover, new types of antioxidants are still being developed and further improvement in the design of high temperature antioxidants is required. Furthermore, several key issues in the field of lubrication and their relation to recent improvements are revealed as follows: corrosive properties of oily additives, shear strength and durability of high pressure agents, internal cohesion and viscosity of organic liquids, improvements in the viscosity index scale, and synthetic oils

Table 4. The effect of multi-function additives (Ca-HDS-L and Ca-HDS-M) on quality properties of a polyol lubricant in

In the future, along with improvement in lubricants performance, the service change lifetime also is intended to be extended. Polybutenes play a key role for control the viscosity in an extensive range of automotive and industrial lubricants. The disadvantages of using lowviscosity polybutenes are due to restrictions in volatility and oxidation resistance limit for base oil applications. ZnDTPs, hindered phenols, alkylated diphenylamines, organomolybdenum compounds and dithiocarbamates are antioxidants that are used for the protection of lubricants against oxidation. On the other hand, future antioxidants should be developed with consideration related the to environmental and emissions concerns, improved fuel/energy

efficiency, higher performance standards, and new base stocks [1].

addition to the oil) are presented in Table 4.

38 Lubrication - Tribology, Lubricants and Additives

7. Future of antioxidants

universal oxidation test (IP 306); TAN: Total acid number [45].

and their improvement [14].

Majid Soleimani1 \*, Leila Dehabadi<sup>2</sup> , Lee D. Wilson<sup>2</sup> and Lope G. Tabil1

\*Address all correspondence to: mas233@mail.usask.ca

1 Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK, Canada

2 Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada
