Oxidation and low temperature stability of polymerized soybean oil-based lubricants

Abstract

Oxidation and low temperature stability of polymerized soybean oil (PSO)-based lubricants have been investigated by the pressurized differential scanning calorimetry (PDSC) method. It was found that PSO samples have lower oxidative stability than their precursor, soybean oil. The main reason for the decreased stability is the generation of tertiary carbons during polymerization. By using antioxidant additives, the PSO samples responded very well and increased their onset temperature (OT) by 70–80 °C. Thermogravimetric analyses have been performed on the PSO samples and it was observed that they are thermally stable at temperatures up to 250 °C. Cold flow property data shows that the PSO samples are good for use in formulating high temperature lubricants. Two model compounds which have terminal double bonds, triacyl-10-undecenoate and allyl 10-undecenoate, have been polymerized. The oxidation stability of these two compounds was investigated by the PDSC method and compared to that of the PSO samples. This study will help us understand the relationships between oxidation stability and molecular structure of PSO-based lubricants. In addition, oxidation stability data of polyethylene (PE) and polypropylene (PP) were used in helping to explain the oxidation stability results of the PSO samples.