The effect of compounding ingredients on microbial degradation of vulcanized natural rubber

Abstract

A series of natural rubber vulcanizates containing varied amounts of sulfur and an accelerator (N‐cyclohexyl‐2‐benzothiazyl sulfenamide, CBS) were prepared and their resistance to attack by a strain of Nocardia, capable of utilizing natural rubber as carbon substrate, was examined. The higher the content of sulfur or CBS, the less the weight loss of the vulcanizates after microbial attack. In this system of curing without a filler, the rate of microbial degradation was suggested to depend on the cross‐link density estimated from the swelling. Addition of calcium carbonate as a filler did not affect the microbial degradation, and in some cases slightly enhanced it. Addition of carbon black, however, made the vulcanizate apparently more resistant to microbial attack. The specimens with HAF grade carbon black loading were more resistant than those with SRF grade.