Homopolymerization effects in polymer layered silicate nanocomposites based upon epoxy resin: Implications for exfoliation

• Published in: Journal of applied polymer science 2009-10, Vol.114 (2), p.1040-1047
• Main Authors: Pustkova, Pavla, Hutchinson, John M, Román, Frida, Montserrat, Salvador
• Format: Article
• Language: English
• Subjects: Activated; Applied sciences; Clay (material); Composites; epoxy resin; Epoxy resins; Exact sciences and technology; Exfoliation; Forms of application and semi-finished materials; homopolymerization; montmorillonite; Nanocomposites; PLS nanocomposites; Polymer industry, paints, wood; Polymers; Resins; Silicates; Technology of polymers
• ISSN: 0021-8995; 1097-4628; 1097-4628
• DOI: 10.1002/app.30697

Exfoliation of polymer layered silicate nanocomposites based upon epoxy resin has previously been reported to be enhanced by allowing some homopolymerization of the resin to occur, catalyzed by the onium ion of the organically modified clay, before the addition of the cross-linking agent and the curing of the nanocomposite. In this work we examine the effects of homopolymerization induced by pre-conditioning the resin/clay mixtures by storing them at various temperatures, from room temperature to 100°C, prior to curing. It is found that pre-conditioning results in similar increases in both the epoxy equivalent (EE) and the glass transition temperature (Tg) of the resin as a consequence of homopolymerization, with a linear relationship between EE and Tg that depends on the pre-conditioning temperature. This is attributed to two different homopolymerization reaction mechanisms, activated monomer (AM) and activated chain end (ACE), the former dominating at high temperature and the latter at low temperature. The effects of these homopolymerization reactions on the network and nanostructure of the nanocomposite are discussed, the important aspect emerging being that the ACE mechanism is the one that most significantly enhances the exfoliation process.