MORPHOLOGICAL STABILITY, INTERFACIAL-TENSION, AND DUAL-PHASE CONTINUITY IN POLYSTYRENE-POLYETHYLENE BLENDS

The morphological stability of polystyrene high-density polyethylene ( PS/PE) blend is investigated in the region of dual-phase continuity. T he effect of the addition of a triblock SEES copolymer to the blends o n the stability of these morphologies, is examined. The results show t hat the morphology of the unmodified blends changes from co-continuous to droplet matrix for PS-rich blends whereas the morphology of a 50/5 0 blend maintains continuity but coarsened significantly upon annealin g at 200 degrees C. In the presence of the copolymer, these morphologi es are much more stable. Selective solvent extraction of polystyrene i n di-ethyl ether reveals that the level of PS continuity in the 50/50 blend is higher for the unmodified system than for the modified one. U pon annealing, the level of PS continuity significantly increases for the unmodified 50/50 PS/PE blend. The effect of the copolymer content in the blend on the interfacial tension between the two components is also investigated using the breaking thread method. The interfacial te nsion is found to be reduced from 5.6 to 1.1 mN/m by the addition of 2 0 parts of the copolymer to the blend. (C) 1997 John Wiley & Sons, Inc .