Conclusions
The widespread use of plant oils as biolubricant
basestocks will depend largely on how well they perform
during high-temperature oxidation and low-temperature
applications. Oxidative stability and low-temperature
characteristics of plant oils should be improved before
these oils are considered for universal biolubricant application. The complexity of plant oil oxidation is primarily
due to the involvement of different structural parameters
in the fatty acid chain. Different structural parameters
participate in the reaction at different stages of oxida tion. Based on the results obtained from this work, the
chemical modification of ricinoleic acid led to decreased
pour points because of, the increased ability to disrupt
crystalline formation at reduced temperatures; increased
viscosity index because of, the increased molecular
weight of the synthesized compounds; increased onset
temperature together with decreased volatile loss and
insoluble deposits because of, elimination of the
double bonds of ricinoleic acid; and decreased coeffi nts of friction because of, the increasing number of
polar functional groups in the structures of the synthe sized compounds. These changes led to stronger adsorption onto the metal surface and enhanced lateral
interactions. For example, elimination of the double
bonds together with attachment of mid- and end-chain
ester groups generally led to improved physicochemical and tribological properties of the synthesized
products.