A mechanical, thermal and electrical properties study of novel vulcanised blends of poly(epichlorohydrin) elastomer with polyaniline dodecylbenzenesulfonate

Abstract

With good mechanical and thermal properties, elastomers having appreciable electrical conductivity may potentially be developed as smart materials for applications such as strain sensors, artificial muscles or flexible biosensors. With such applications in mind, the purpose of this study was to investigate the structure-properties relationships of new vulcanised blends of a poly (epichlorohydrin) elastomer (PECH) and electrically-conducting polyaniline dodecylbenzenesulfonate salt (PAni.DBSA). PAni.DBSA, synthesised by a published method, was blended with PECH and vulcanised with a commercial sulfur cross-linking agent in an internal mixer. The morphological, mechanical, thermal and electrical properties were examined as a function of the amount of PAni.DBSA in the blends. The electrical conductivities increased with the proportion of polyaniline, showing a low percolation threshold of about 1 wt. % (1.07 vol %) PAni.DBSA (from about 10−12 to 10−10 S cm−1), and a second stage of percolation around 5 wt.%, ultimately reaching around 3 × 10−8 S cm−1. The results from microscopy and other techniques indicated that a mixture of micro- and nano-sized PAni.DBSA particles was dispersed in the elastomer matrix at compositions above 5 wt. % PAni.DBSA. The infrared spectra of vulcanised PECH-PAni.DBSA blends showed features of the pure polymers, with some notable peak shifts due to intermolecular interactions between the constituents. Thermal properties of the conductive blends were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal stabilities of the blends were strongly dependent on the ratio of PAni.DBSA to PECH, and the two components inhibited the thermal decomposition of each other. The elastomer’s glass transition temperature (Tg) was determined by thermomechanical analysis (TMA); each blend showed only one such transition, at temperatures that increased monotonically with the proportion of PAni.DBSA present, indicating a significant degree of molecular interaction between the two polymers.