Crosslinkable poly(vinyl acetate)/clay nanocomposite films cast from soap-free emulsion-polymerized latices

Exfoliated poly(vinyl acetate) (PVAc)/montmorillonite (MMT) and poly(vinyl acetate-co-glycidyl methacrylate) [P(VAc-co-GMA)]/MMT nanocomposite latices, prepared by soap-free emulsion polymerization, were able to be cast into films, and the latter was crosslinked with diethylene triamine as a curing agent. The glass-transition temperature of the crosslinked P(VAc-co-GMA)/MMT nanocomposite films was higher than that of the PVAc/MMT counterparts. Although both the Young's modulus and yield stress for the PVAc/MMT nanocomposite films increased with the content of MMT, the extent of the increase was greater for the crosslinked P(VAc-co-GMA)/MMT nanocomposites. The exfoliated MMT nanoplatelets retarded the cold drawing of the PVAc matrix during tensile testing, resulting in a decrease of the elongation. However, crosslinked P(VAc-co-GMA)/MMT nanocomposite films still had more elongation than the PVAc/MMT counterparts. The drastic decrease of the water vapor permeability with the content of MMT for both types of nanocomposite films suggested that the exfoliated MMT nanoplatelets were dispersed evenly and flattened completely along the film surface. After all the nanocomposite film samples were burned, the inflammable residues for the samples with an MMT content higher than 5 wt% could preserve the original film profile with stiffness, and this indicated that the exfoliated MMT nanoplatelets acted as inflammable scaffolds. (C) 2008 Wiley Periodicals, Inc.