A Highly Efficient β-Nucleating Agent for Impact-Resistant Polypropylene Copolymer

In this work, we reported calcium tetrahydrophthalate as a high efficient beta-nucleating agent (beta-NA) for impact-resistant polypropylene copolymer (IPC). The relative fraction of the beta-crystal can reach as high as 93.5% when only 0.03% beta-NA is added. The non-isothermal and isothermal crystallization behaviors, morphology, lamellar structure and mechanical properties of IPCs with various beta-NA contents were studied. During non-isothermal crystallization, the cooling rate has an important influence on the relative fraction of the beta-crystal, which decreases remarkably as the cooling rate increases. The beta-NA also greatly accelerates crystallization rate of IPC, resulting from both more crystal nuclei and larger Avrami exponent. The small angle X-ray scattering characterization shows that more amorphous components are included into the inter-lamellae after addition of beta-NA. Dynamical mechanical analysis (DMA) reveals that the storage modulus at low temperature and the loss factor above 0 degrees C from the PP component can be enhanced upon addition of beta-NA and reach a maximum at the beta-NA content of 0.05 wt %. Impact test shows that the impact strength of the IPC at 0 degrees C can be improved as much as 40% when the content of calcium tetrahydrophthalate is 0.10 wt %. (C) 2014 Wiley Periodicals, Inc.