Factors influencing shrinkage of natural rubber/EPDM blend

Abstract

In this research work, various factors influencing the shrinkage of natural rubber/EPDM blends (ratio of 70:30) and the physical properties of vulcanized rubber were studied. The types and concentrations of filler and vulcanization systems were also investigated. It was found that the shrinkage of the clay filled compound was the lowest, while the shrinkage of calcium carbonate filled compound was the highest. The results also showed that the carbon black filled compound and silica filled compound had similar trend. For all vulcanizates, the increased amount of filler resulted in decreasing shrinkage due to the decrease in rubber content. The change of shrinkage was consistent with the linear coefficient of thermal expansion of each filled compound. It was also found that the efficient vulcanized compound shrinkage was lower than semi-efficient and conventional vulcanized compound, respectively. This is due to the fact that the efficient vulcanized compound exhibited the highest crosslink density. The stiff vulcanizates yielded a low shrinkage value.