Pyrolysis-GC-MS and TGA-FT-IR methods have been used to perform a comparative degradation study of polystyrene and a polystyrene-clay composite. An abnormally high yield of a-methylstyrene has been detected for the composite. This and other differences in degradation products have been explained by enhanced intermolecular interaction of the grafted PS chains, forming, a brush structure. A conceptual model of the process has been suggested.