Crystallization behavior of impact copolymer polypropylene revealed by fast scanning chip calorimetry analysis

The crystallization behaviors of two impact copolymer polypropylenes (ICP) were investigated by using fast scanning chip calorimetry (FSC) and micro-focus wide-angle X-ray diffraction (WAXD) techniques. Different crystallization peaks of these two samples during cooling were observed at cooling rates from 50 to 4000 K/s. For ICP-A, the crystallization of polypropylene (PP) matrix into α crystallites, polyethylene (PE) sequences in ethylene-propylene segmented copolymer (EsP), PP segments in ethylene-propylene block copolymer (EbP), and PP matrix into mesophase successively occurred from high to low temperatures. As the cooling rate increased, the crystallization of PP matrix into α crystallites, PP segments, and mesophase were suppressed one by one. Nevertheless, the crystallization of PE segments was hardly suppressed. For ICP-B, it showed almost the same crystallization behavior as ICP-A, except for the absence of independent crystallization peak of PP segments. The different crystallization performance in these two samples could be ascribed to their different chain microstructures.