PVC: polystyrene alloys of varying compositions were prepared by the film casting technique. Thermogravimetric analysis of these materials showed that the decomposition patterns of the alloys are quite different from those of the constituent polymers. These results are explained in terms of polymer interaction phenomena.The blending of two or more polymers to form novel materials is an operation that usually reduces composition non-uniformity [1]. This has important technological implications, as chemical, physical and mechanical properties, as well as appearance, all depend upon composition uniformity. In fact, it is known [2-4] that these alloys very often exhibit a synergism in properties achievable only through this technique. Blending methods usually [5] involve solid -to -liquid, solid -to -solid or liquid -to -liquid mixing.The two polymers chosen for this investigation have extensive industrial and household applications. In a recent article [6], we showed by means of DSC that PVC and polystyrene (PSt) are a compatible macromolecular pair (single Tg when blended). The present paper reports the results of TG studies on this blend. Experimental MaterialsThe PVC and PSt samples were supplied by Aldrich Ltd., and have intrinsic viscosities of 0.75 and 0.86, respectively. Analytical grade tetrahydrofuran (TFH) solvent was procuced from BDH.