Flow‐induced solidification of high‐impact polypropylene copolymer compositions: Morphological and mechanical effects

Polypropylene‐based impact copolymers are a complex composition of matrix material, a dispersed phase and many optional modifiers. The final heterophasic morphology of such systems is influenced significantly by the processing step, adding an additional level of complexity to understanding the structure‐property relation. This topic has hardly been studied so far. The effect of thermal history and shear flow on the solidification process of three different compositions of a polypropylene‐based impact copolymer, i.e., one base material and two compounds with either high density polyethylene or ethylene‐co‐octene added, is investigated. Samples are examined using differential scanning calorimetry, extended dilatometry, transmissions electron microscopy, and finally, tensile testing. With flow, the materials show pronounced flow‐enhanced crystallization of the matrix material and deformed filler content. Compared to the base polymer, the stress–strain response of the compounded samples shows a lower yield stress and more pronounced influence of shear, reflected in the increasing strain hardening modulus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42040.