Design and analysis of experiments in silica filled natural rubber compounds - effect of castor oil

The potential of castor oil fatty acid as an activator for the vulcanization reaction in silica filled natural rubber (NR) compounds was investigated. Design and analysis of experiments were carried out by keeping constant the concentrations of silica and the other ingredients while the amounts of stearic acid, castor oil and poly(ethylene glycol) were varied. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI-100 oscillating disk rheometer at 150, 160 and 170 degreesC. The overall rates and the apparent activation energies for the vulcanization process were calculated for each compound, assuming that vulcanization follows first-order kinetics. The results show that the simple addition of castor oil does not significantly change the vulcanization process. (C) 2003 Elsevier Science Ltd. All rights reserved.