Cone calorimeter combustion and gasification studies of polymer layered silicate nanocomposites

Polymer composites based on organically modified phyllosilicates (organoclay) and poly(ethylene-co-vinyl acetate) (EVA) were prepared by melt processing to study their combustion behavior. Their degrees of dispersion and intercalation spacings as determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD) were typical of either a microcomposite or an exfoliated nanocomposite, depending on the type of organoclay. Combustion experiments showed that the microcomposite burns in the same way as pure EVA, whereas the heat release is reduced by 70-80% when nanocomposites with low silicate loadings (2-5%) are burned, because a protective charred ceramic surface layer is formed as a result of reassembly of the clay layers and catalyzed charring of the polymer. A chemical mechanism for this charring is proposed.