Plasticization of cross-linked epoxy networks by hydrocarbon chains of quaternary ammonium ions and its effect on exfoliation behavior of nanoclay particles in mixtures of aromatic and aliphatic epoxies were investigated. It was found that quaternary ammonium ions, apart from catalyzing epoxy curing reactions, are capable of plasticizing cross-linked epoxy chains, the effect of which was observed in terms of large reduction in glass transition temperature and lowering of the values of storage modulus of cured epoxy networks. The effect of plasticization on storage modulus was found to be small for aromatic epoxy and large for aliphatic epoxy. As a consequence, the aromatic epoxy−clay system produced complete exfoliation of clay galleries, while the systems with mixtures of aliphatic and aromatic epoxy resulted in intercalated systems, even though the extent of curing of epoxy was the same in all cases.
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