THERMAL AND MECHANICAL-PROPERTIES FOR BINARY BLENDS OF METALLOCENE POLYETHYLENE WITH CONVENTIONAL POLYOLEFINS

The thermal and mechanical properties for four binary blends, high-den sity polyethylene (HDPE)-metallocene polyethylene (MCPE), polypropylen e (PP)-MCPE, poly(propylene-co-ethylene) (CoPP) -MCPE, and poly( propy lene-co-ethylene-co-1-butene) (TerPP) -MCPE were investigated to compa re the compatibility and molecular micromechanism of the blends. We re port in this work all the blend systems that are thermodynamically imm iscible but mechanically compatible which have been understood by thei r thermal and mechanical behaviors. A lower content of MCPE (up to 50% ) in PP-MCPE, CoPP-MCPE, and TerPP-MCPE blends showed discernibly two beta transitions, whereas beta relaxation was shifted to a lower tempe rature with the MCPE content in the HDPE-MCPE system. These results co nclude that the degree of compatibility in the HDPE-MCPE blend is the largest among the blend systems that we have studied, which also can b e explained in terms of the similar chemical structure of polyolefins. (C) 1998 John Wiley & Sons, Inc.