Influence of nucleation on the brittle-ductile transition temperature of impact-resistant polypropylene copolymer: From the sight of phase morphology

Influence of α‐ and β‐nucleation on brittle‐ductile transition temperature (BDTT) of impact‐resistant polypropylene copolymers (IPCs) and their phase morphologies were comparatively investigated. Impact test showed that the BDTT of β‐nucleated IPC (β‐IPC) is ∼ 24°C lower than that of α‐nucleated one (α‐IPC). Structural characterizations including atomic force and scanning electron microscopic observations, small angle X‐ray scattering examination, and dynamical mechanical analysis revealed that dispersion of the ethylene‐propylene random copolymer‐rich (EPR‐rich) phase was finer in β‐IPC in comparison with that in α‐IPC. For the reason of looser lamellar arrangement, the portion of EPR‐rich components included in the interlamellar region of β‐IPC was higher than those of α‐IPC, which led to improved mobility for the amorphous polypropylene chains. It was proposed that the finer distribution of EPR‐rich phase, which might result from faster growth rate of the β‐crystal and looser lamellar arrangement of β‐spherulite, should be responsible for the improved impact‐resistance and lower BDTT in β‐IPC samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012