Thermal stability and flammability of polypropylene/montmorillonite composites

Abstract

Smectite clays, such as montmorillonite, are of great industrial value because of their high aspect ratio, plate morphology, intercalative capacity, natural abundance and low cost. In the present work, polypropylene/montmorillonite (PP/MMT) composites have been prepared and their thermal stability and flammability have been investigated. Although the composites are not nano-dispersed, they exhibit higher thermal stability and considerably reduced peak heat release rate (PHRR). This is probably due to physico-chemical adsorption of the volatile degradation products on the silicates. On the other hand, the addition of MMT can catalyse the initial decomposition of PP matrix and accelerate its ignition in combustion. It has been observed that a ceramic-like char formed on the surface of the composites during the combustion test. The characterization of the char surface prior to ignition indicates that it is an inorganic-rich surface, leading to improvement of the thermal stability and reduction of flammability of the composites because of its better barrier properties.