Ternary blends to improve heat distortion temperature and rheological properties of PVC

Binary and ternary blends of PVC mixed with α-methylstyrene/ acrylonitrile-butadiene-styrene copolymer (AMS-ABS) and ethylene/vinyl acetate/carbon monoxide terpolymer (EVA-CO) are investigated, with the aim to obtain a new PVC based material with an improved heat distortion temperature and good processability. Dynamic Mechanical Thermal Analysis (DMTA) reveals that ternary PVC/AMS-ABS/EVA-CO blends exhibit two glass transition temperatures: the lower T_g corresponds to a PVC/EVA-CO phase and the higher one to a PVC/AMS-ABS phase. An analysis of PVC respective interactions with AMS-ABS and EVA-CO leads to assert that the distribution of PVC in the ternary PVC/AMS-ABS/EVA-CO system is basically controlled by the binary immiscible blend composition, taken as Φ AMS-ABS/Φ EVA-CO ratio. The inclusion of AMS-ABS and EVA-CO to form ternary blends based on PVC, allows to improve heat distortion temperature (owed to the presence of AMS-ABS), maintaining a low viscosity in the molten state, due to the plasticizing effect of EVA-CO.