Preparation of natural rubber/polypyrrole composites by chemical oxidative polymerization

Abstract

In this study, the natural rubber/polypyrrole composites were prepared by the chemical oxidative polymerization of pyrrole in natural rubber latex. The reactions were carried out at 0oC for 1 hour using FeCl3 solution as an oxidant and FeCl3: pyrrole ratio was kept constant at 2.5 by mole. After reaction, the thoroughly washed and dried composites were weighed in order to determine the amount of polypyrrole in the composites. The electrical conductivity of the composites was measured with a home-made four-point probe apparatus. Parameters affecting the electrical conductivity of the composites were studied, i.e. the amount of natural rubber, the types of natural rubber, the addition sequence of pyrrole and ferric chloride, the addition of stabilizer, and the addition of montmorillonite. It was found that pyrrole prior addition gave the composite with higher electrical conductivity than FeCl3 prior addition. The natural rubber/polypyrrole composite at natural rubber to pyrrole ratio of 0.8 (by weight) with pyrrole prior addition was selected to be the most appropriate one. The higher electrical conductivity was obtained when deproteinized protein was used, but the addition of polyethylene glycol gave lower electrical conductivity. In the presence of montmorillonite, the composites exhibited higher electrical conductivity with increasing montmorillonite content. The morphology and thermal stability of the composites were also investigated.