Effect of wheat starch as filler on NR/SBR blends

Abstract

Carbon black (CB) has been used for over one-hundred years as a reinforcing filler in rubber matrix. In order to reduce our dependence on fossil resources, attempts have been made to develop renewable biofillers such as starch in the rubber industry. In this study, NR/SBR blends (50/50) were prepared with different loading of wheat starch (5, 10, 20, 35 and 50 phr). A semi-efficient sulphur vulcanization system (semi-EV) was employed. The curing characteristics of the compounds were determined with a Monsanto Rheometer at 130, 140 and 150 °C. The properties of unfilled and filled NR/SBR blends prepared at 150 °C were evaluated by swelling measurements, tensile tester, dynamic mechanical analyser (DMA) and scanning electron microscope (SEM). The results showed that the optimal cure time, minimum torque, and maximum torque of filled NR/SBR blends were improved. It was found that the tensile strength and the elongation at break of wheat starch filled NR/SBR blends were maximal with the incorporation of 20 phr of wheat starch. The chemical crosslink densities were found to follow the mechanical properties. The results of DMA indicated that incorporation of wheat starch led to an increase in the glass transition temperature whilst reducing the mobility of macromolecular chains of NR/SBR mixtures, and on the other hand improved their slip resistance on wet surfaces, thus indicating its potential application in the manufacture of tyre tread.