Highly exfoliated nanostructure in trifunctional epoxy/clay nanocomposites using boron trifluoride as initiator

Epoxy/clay nanocomposites based upon a trifunctional epoxy resin, triglycidyl p-amino phenol (TGAP), have been prepared by intercalating an initiator of cationic homopolymerization, a boron trifluoride monoethylamine (BF3·MEA) complex, into the montmorillonite clay galleries before the addition of the TGAP and the curing agent, 4,4-diamino diphenyl sulfone (DDS), and effecting the isothermal curing reaction. The BF3·MEA enhances the intragallery cationic homopolymerization reaction, which occurs before the extragallery cross-linking reaction of the TGAP with the DDS, and which hence contributes positively to the mechanism of exfoliation of the clay. The effects of isothermal cure temperature and of BF3·MEA content have been studied, in respect of both the reaction kinetics, monitored by differential scanning calorimetry, and the nanostructure, as identified by small-angle X-ray scattering and transmission electron microscopy. It is shown that the use of BF3·MEA in this way as an initiator of intragallery homopolymerization significantly improves the degree of exfoliation in the cured nanocomposites.The authors are grateful to Huntsman Corporation for the epoxy resin and curing agent. This work was supported financially by MINECO Project MAT2011-27039-C03 and the Generalitat de Catalunya (2009-SGR-1512). FS is grateful for a grant from the Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR), FI-DGR 2011 and XF-F acknowledges the contract JCI-2010-06187.Peer ReviewedPostprint (author's final draft