Influence of filler network on thermo-chemical de-vulcanization efficiency of carbon black filled natural rubber

Abstract

Carbon black is often used as the reinforcing filler in tires since it plays an important role in improvement of tires mechanical properties such as abrasion, stiffness, modulus and fatigue life. In this study, natural rubber (NR) filled with various loadings of carbon black was prepared. Then, the NR vulcanizates were de-vulcanized via thermo-chemical method using diphenyl disulfide as de-vulcanization aid. The de-vulcanization efficiency was analyzed by relationship between sol fraction and crosslink density of the de-vulcanizates. It is found that the de-vulcanization efficiency is influenced by filler loading. This is attributed to the degree of filler network formation in a rubber matrix which is depended on the filler loadings. In the unfilled de-vulcanizates the results showed that almost 100% of sol fraction and the crosslink density reduced to almost zero are observed. Adding carbon black results in a decrease of sol fraction and increase of crosslink densities. This is due to during de-vulcanization some occurred reactive radicals reacted with active site of carbon black surfaces in filler network to form gels of complex compound. Hence, the de-vulcanization efficiency is lower with increasing carbon black loadings.