Comparative study of tribological properties of trimethylolpropane-based biolubricants derived from methyl oleate and canola biodiesel

A class of industrial-grade biolubricants was synthesized from methyl oleate and canola (Brassica napus) biodiesel by transesterification with trimethylolpropane (TMP) using sodium methoxide as catalyst. Model transesterification reactions were performed with methyl oleate to optimize the reaction conditions to obtain maximum yield of TMP trioleate. Methyl oleate-derived biolubricant with TMP triester composition of 91.2% was obtained after 5 h. Under similar reaction conditions, canola biodiesel-derived biolubricant comprising of 90.9% of TMP triesters was obtained. Both biolubricants were evaluated for their tribological properties using ASTM and AOCS standards. They exhibited very high viscosity indices, excellent low temperature properties and moderate oxidative stabilities. The lubricity of the biolubricants was tested on a High Frequency Reciprocating Rig (HFRR) apparatus by measuring wear scar diameter on a test sample. Canola biodiesel-derived biolubricant was found to perform better than methyl oleate-derived biolubricant based on HFRR test. Both biolubricants met ISO VG 46 specifications.