Micro- and Nano-Tribological Behaviour of Soybean Oil-Based Polymers of Different Crosslinking Densities

Biopolymers produced from renewable and inexpensive natural resources, such as natural oils, have drawn considerable attention over the past decade, due to their low cost, ready availability, environmental compatibility, and their inherent biodegradability. In this study, the micro/nanotribological wear behavior of biopolymers of different crosslinking densities prepared from low saturated soy-bean oil (LSS) by Rh-catalyzed isomerization 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 micron radius conical diamond probe with 90° cone angle. Nanoscale tests were done using a DLC coated antimony (n) doped silicon probe of radius ∼200 nm. Wear volumes were estimated from groove geometry using Atomic Force Microscope (AFM) and adhesive and abrasive wear coefficients were evaluated for the materials. Elastic modulus and hardness information were evaluated using tensile test and microhardness tests respectively. Correlations between cross-linking density and wear behavior were observed. These results provide some insight into the wear behavior of biorenewable materials.