Relaxation behavior of natural rubber composites based on mooney stress relaxation and rheometer data

Abstract

Studies on relaxation behavior of natural rubber composites were conducted by Mooney stress relaxation coupled with rheometer data. The effect of filler (carbon black N-330) and sulphur loading was monitored on the relaxation behavior. Elasticity of the composites was also determined in term of elongation at break and hardness, as confirmation to the relaxation behavior. The experiments were conducted by varying the N-330 30, 35, 40 and 45 phr with the sulphur baseline of 2 phr. While sulphur loading was varying from 1, 2, 3 and 4 phr with the N-300 baseline of 30 phr. Mooney experiments were carried out at 100 ºC, while rheometer experiments were conducted in a moving die rheometer at 150ºC. Results finding showed that the relaxation rate was reduced with N-330 loading or sulphur loading due to restriction of rubber molecule chain mobility by crosslinking formation. N-330 provided higher effect on stress relaxation rate compared to sulphur. Elongation of the composites was found to decrease upon filler or sulphur loading, while hardness was inversely.