Adverse effects of thermal dissociation of alkyl ammonium ions on nanoclay exfoliation in epoxy–clay systems

It has been shown recently that storage modulus of intra-gallery epoxy plays a crucial role in producing exfoliated clay structures in epoxy-nanoclay systems. In this study, the possibility of thermal dissociation of alkyl ammonium ions used as cation exchange agents of layered silicate clays and its effects on plasticization of epoxy networks and the growth of storage modulus of intra-gallery epoxy were investigated. It was found that at cure temperatures higher than the dissociation temperature, primary amines were generated from the thermal dissociation of alkyl ammonium ions and the excess chloride salt, which reacted readily with the epoxy molecules and formed linear chains. In addition, such reactions resulted in an excess of diamine curing agents, which in turn caused additional plasticization of epoxy networks and lowered the values of intra-gallery storage modulus. In such cases, only intercalated epoxy composites were produced.