Rheological and Tribological Characteristics of Chemically Modified Rapeseed Oil

Abstract

Vegetable oils are environmentally friendly base stocks. They have excellent lubricity, but poor oxidative stability because of double bonds. The double bonds in the vegetable oils could decrease through chemically modified reaction in the existence of the catalyst, and the oxidative stability of the vegetable oils can be improved obviously. A series of chemically modified rapeseed oils (alcohol modified rapeseed oils) were prepared by reacting epoxidized rapeseed oil with different carbon chain length alcohols through ring-opening reaction followed by transesterification, and their molecular structures were identified by Fourier transform infrared (FT-IR) spectrophotometer. The rheological characteristics (viscosity, viscosity index, pour point)and tribological characteristics(the coefficient of friction at different load, the wear scare diameter \( \left( {D_{30'}^{294N} } \right) \),the load carrying capacity (PB))of alcohol modified rapeseed oils were evaluated and analyzed. The results show that the pour point increases with the length of carbon chain of linear alcohol, and gradually decreases with the degree of isomerization of the molecule; the tribological characteristics increase with the length of carbon chain decrease with the degree of isomerization at the same length of carbon chain. The iso-octanol modified rapeseed oil has the best synthetic properties of the chemically modified rapeseed oils (the viscosity is 25.2mm2/s, the viscosity index is 140, and the pour point is −29°, the load carrying capacity is 862.4N, the wear scare diameter is 0.50mm), and its oxidative stability is obviously better than rapeseed oil and mineral oil, it can be used as a kind of base lubricant with excellent quantity. Their molecular structures were identified by Fourier transform infrared (FT-IR) spectrophotometer.