Structure and properties of polypropylene/poly(ethylene-co-propylene in-situ blends synthesized by spherical Ziegler-Natta catalyst

A polypropylene/poly(ethylene-co-propylene) (iPP/EPR) in-situ blend synthes ized by spherical Ziegler-Natta catalyst was fractionated by temperature-gr adient extraction fractionation. The fractions were characterized using FTI R, C-13 NMR, DSC and WAXD. The in-situ blend was found to contain mainly th ree portions: an ethylene-propylene random copolymer, a series of segmented copolymer with PE and PP segments of different length, and propylene homop olymer. The impact strength of in-situ blends of different structural heter ogeneity was measured, and the results show that increasing the amount of s egmented copolymer has a positive effect on the impact strength. The segmen ted copolymer portion alone is found to increase the impact strength at roo m temperature greatly, while the low temperature impact strength can be mar kedly enhanced only when random copolymer coexists with the segmented copol ymer. (C) 2001 Elsevier Science Ltd. All rights reserved.