An investigation on the potential of rice husk ash as fillers for epoxidized natural rubber (ENR)

Abstract

Burnt rice husk ash yields two grades of fillers, namely white rice husk ash, WRHA and black rice husk ash, BRHA. WRHA used in this study has been analysed to have about 96% silica content, while the BRHA has a lower silica content, typically about 54%, and a substantial carbon content, i.e. about 44%. These ashes were incorporated into epoxidized natural rubber, ENR (50 mol.% epoxidation grade) using a laboratory size two roll mixing mill. Curing using a semi-efficient vulcanization (semi-EV) was chosen and cure studies were carried out on a Monsanto rheometer. The physical testing of the ENR vulcanizates involves the determination of tensile, tear and hardness properties. The effect of the coupling agent on the curing and physical properties of the vulcanizates has been investigated using γ-mercapto-propyltrimethoxysilane. For comparison purpose, two commercial fillers, i.e. precipitated silica (grade Vulcasil-S) and carbon black (grade N330) were used. WRHA exhibits the best overall vulcanizates properties as compared to BRHA, though it is still inferior to commercial fillers especially with regard to tensile strength and tear strength. The present of the silane coupling agent has enhanced the cure times ( t 90), tensile and tear strengths of filled ENR vulcanizates.