A Comparative Study of the Effect of Thermo-Oxidative Aging on the Physical Properties of Rice Husk Ash and Commercial Fillers in Epoxidized Natural Rubber Compounds

Abstract

The effect of thermo-oxidative aging on physical properties viz. modulus, tensile strength, elongation at break, tear strength and hardness of rice husk ash (RHA) and commercial fillers in ENR compounds have been studied. While the modulus and hardness increased with aging, other properties, i.e., tensile strength, elongation at break and tear strength decreased. The poor retention in properties indicates that thermo-oxidative aging process has resulted in permanent damage to the vulcanizates. The hardening and brittleness of the aged vulcanizates provides clear evidence for the aging process. The comparable retention values of both white rice husk ash (WRHA), black rice husk ash (BRHA), carbon black and silica filled vulcanizates indicates that the thermo-oxidative aging behaviour is determined predominantly by the ENR matrix. Scanning electron microscopy on fracture surfaces after aging shows the filler particles were poorly wetted by the rubber matrix. This explains the dramatic reduction in tensile strength, elongation at break and tear strength after aging.