Effect of crosslinking on the friction and wear behavior of soybean oil-based polymeric materials

Abstract

In this study, the friction and wear behavior of soybean oil-based polymers prepared by cationic polymerization of low saturated soybean oil (LSS) with divinyl benzene and polystyrene are evaluated as a function of crosslink density. Tribological measurements were performed on samples of three crosslink densities (10%, 15% and 20% of crosslinking agent concentration by weight) using a ball-on-flat reciprocating microtribometer with normal loads ranging from 0 to 800 mN. Friction and wear behavior during dry sliding was evaluated using a spherical (1.2 mm radius) silicon nitride probe as well as a conical (100 μm radius, 90° cone angle) diamond probe. Friction behavior was evaluated from single strokes at ramped normal loads, whereas wear experiments were evaluated from 10 to 500 reciprocating cycles at fixed normal loads. All samples showed comparable coefficients of friction. In general a higher crosslinking density resulted in lower adhesive wear. Increased abrasive wear was observed for the lowest and highest crosslinking densities. Atomic force microscopy and scanning electron microscopy of wear tracks were used to elucidate deformation mechanisms in the various samples. These results provide some insight into the friction and wear behavior of soybean oil-based polymers.