In the present study, various properties, viz. physiochemical, rheological, tribological and thermal properties of polyolester (POE) lubricant, a widely used lubricant in household refrigerator compressor, is evaluated by loading it with alumina nanoparticles and also blending it with sesame oil (SESO)-an environment-friendly lubricant and the results are compared in order to visualize the effects. The mass fraction of alumina nanoparticles used is from 0.05 to 0.15% and the blend ratio of sesame oil is from 12.5 to 87.5%. The rheological properties were evaluated for the temperature ranges from 25 to 100 degrees C. High-frequency reciprocating rig is used to perform tribological studies. The results show that the values of viscosity, viscosity index, flash and fire point enhanced for all the synthesized lubricants with an increase in alumina nanoparticles proportion and the sesame oil ratio in the base POE oil and all of the synthesized lubricants showed Newtonian behaviour as well. The thermal stability (TGA results) of the POE + SESO blend and POE + Al2O3 nanolubricant was found increasing with the increase in the proportion of sesame oil and the alumina nanoparticles in the base POE oil. The contact angle and surface tension of the synthesized lubricants were initially found decreasing with the addition of sesame oil and alumina nanoparticles to the base POE oil and then increased, as the sesame oil and alumina nanoparticles proportion in the base oil approached the maximum limit. Among the POE + Al2O3 nanolubricants, the POE + 0.125%Al2O3 and among the POE + SESO blend 15POE + 25SESO exhibited much better results in tribological studies. The sesame oil-blended POE oil was found less toxic and more biodegradable when compared to the POE + Al2O3 nanolubricant.
