Tribological and mechanical properties of nano ZnO-filled epoxy resin composites

Epoxy resin composites filled with nano ZnO particulates were prepared by proper curing, using KH-560 silane coupling agent to enhance the interfacial bonding between the inorganic reinforcing agent and the polymer matrix in the presence of ultrasonic agitation. The mechanical properties of the resulting composites were measured, while their friction and wear behaviors under dry sliding against a stainless steel were examined on an M-2000 friction and wear tester. Moreover, the effect of friction on the microstructure of the composites was investigated based on the analysis of the free volume features of the composites by means of positron annihilation lifetime spectroscopy (PALS). As a result, the filled epoxy resin composites showed better wear resistance than the epoxy resin matrix, and the composite filled with 10% ZnO had the smallest wear rate. This was attributed to the strengthening function of the nanometer particulate filler which was well bonded to the polymer matrix in the presence of the coupling agent. Friction led to an increase in the free volume hole size of the composites, while the average size of free volume holes tended to increase with the increase of ZnO content.