The effects of composition and processing variables on the properties of thermoplastic polyaniline blends and composites

Pure polyaniline (PANI) has a high electrical conductivity and can be made soluble and thermoplastic, but it still lacks adequate mechanical properties for large-scale commercial use and therefore, it has been blended with other polymers such as poly(methyl methacrylate) (PMMA). In the work described in this paper, the scaled up synthesis of conductive polyaniline by an oxidative chemical method under controlled pH and temperature has been optimised. Re-doping of deprotonated insulating base with excess of the mono-functional organic acids such as p-toluenesulfonic (TSA) or dodecylbenzenesulfonic (DBSA) in aqueous media was successful. A wide range of techniques including TGA, GPC, EA, FTIR, XRD and SEM were employed for the characterisation of PANI powders and blends. Compositions of PANI-HCI, TSA or DBSA and thermoplastic matrix PMMA with or without a plasticiser were melt-processed by compression moulding for 3 min at 210 degreesC to produce plaques. The effectiveness of four different phenolic plasticisers was compared and hydroquinone was found to produce the blends with the highest conductivities. A few preliminary injection-moulded plaques were made and their conductivities were compared with those of the compression-moulded samples. (C) 2001 Kluwer Academic Publishers.