Original Article

A comparative study of polymeric additives as biodegradable viscosity boosters for biolubricant formulations S Rani, ML Joy and K Prabhakaran Nair Vegetable oils are regarded as renewable energy for future generations due to its biodegradability, high thermal proper-ties, and good lubricity. Some of the disadvantages of vegetable oil are high pour point, low oxidative stability, and limited viscosity range. In this paper, we evaluate and compare the rheological properties of rice bran oil (RBO) with various proportions of low-density polyethylene (LDPE) and ethyl vinyl acetate (EVA) separately. The thermal stability also has been tested in this paper. Both the polymers have different mode of improving the viscosity and LDPE is found to be a viscosity index booster. The percentage improvement in viscosity for various proportions of polymers has been eval-uated at various temperatures. It is seen that LDPE is more suited for engine oil applications since the high temperature rheology is more important in the selection of these lubricants. The viscosity variation of biolubricant formulations with temperature were validated with Walther equation. The biodegradability of both the polymers was estimated and compared with a commercially available mineral oil. The addition of EVA and LDPE in RBO reduces the biodegradability to a smaller extent but it is better than commercially available mineral oil SAE20W40