Micro- and nano-tribological behavior of soybean oil-based polymers of different crosslinking densities

Biobased polymers produced from renewable and inexpensive natural resources, such as natural oils, have drawn considerable attention over the past decades, due to their low cost, ready availability, environmental compatibility, and their inherent biodegradability. In this study, the micro/nanotribological wear behavior of biopolymers with different crosslinking densities prepared from low saturated soybean oil (LSS) by cationic copolymerization with divinyl benzene and polystyrene are evaluated and compared. Microtribological measurements were performed using a ball-on-flat reciprocating microtribometer using two different probes −1.2 mm radius Si3N4 spherical probe and a 100 μm radius conical diamond probe with 90° cone angle. Nanoscale wear tests were performed using a DLC coated antimony (n) doped silicon probe of radius ∼200 nm in an atomic force microscope (AFM). Wear volumes were estimated from AFM topography maps of groove geometry and wear coefficients were evaluated for the materials. Elastic modulus and hardness information were evaluated using nanoindentation tests. Correlations between crosslinking density and observed wear behavior across scales are discussed. These results provide some insight into the wear behavior of soybean oil-based polymers.