Thermal and dynamic mechanical analysis on metallocene ULDPE/PP blends to optimize impact properties

Metallocene polymerized ultralow density polyethylenes (ULDPE) were found t o be effective impact modifiers for rigid matrices such as polypropylene (P P). This is mainly due to the very high level of comonomer incorporation wi th homogeneous short chain branching distributions (SCBD) brought about by the single site metallocene catalysts. However, a very heterogeneous Ziegle r Natta copolymer of 0.88 specific gravity was found to be surprisingly eff ective in impact modification efficiency. A variety of thermal and morphological techniques were used in this study i ncluding differential scanning calorimetry (DSC), dynamic mechanical analys is (DMA), and low voltage scanning electron microscopy (LVSEM). It was foun d that the modulus difference between the two phases, degree of coupling as evidenced by morphology at the phase boundaries, and crystallizable fracti on of the rubber phase all played an important role in impact modification. (C) 2000 Elsevier Science B.V. All rights reserved.