Cavitation in the impact copolymer polypropylene (ICP) and its corresponding homo-isotactic polypropylene (homo-iPP) during stretching was investigated using ultra-small angle X-ray scattering technique. Different from the iPP showing a suppressed cavitation around yielding at high deformation temperature (T_d), the ICP presented a more intensive cavitation at elevated T_d. This unusual T_d dependency of cavitation around yielding observed in ICP was suggested to be caused by the changes of the stability of the rubber particles dispersed in iPP matrix. The rubber particles exhibit a multi-phase core-shell structure which contains crystallizable polyethylene segments in the core layer, the amorphous polymer of ethylene-propylene random copolymer in the inner shell layer, and the crystallizable polypropylene segments in the outer shell layer. The softening and melting from the inner shell to the core and the outer shell took place as the T_d increased. It can be envisaged that the fraction of unstable regions inside the rubber particles and the debonding between the iPP matrix and the dispersed phase gradually increased providing more nucleation sites for cavities at high T_d, a more intensive cavitation was thus observed.

使用超小角度X射线散射技术研究了抗冲共聚物聚丙烯（ICP）及其相应的均等规聚丙烯（homo-iPP）在拉伸过程中的空化现象。与iPP相比，在高变形温度（T _d）下屈服附近的空化受到抑制，而ICP在T _d升高时表现出更强烈的空化。这个不寻常的T _dICP中观察到的气蚀与屈服的依赖性被认为是由于分散在iPP基体中的橡胶颗粒稳定性的变化引起的。橡胶颗粒表现出多相核-壳结构，其在核层中包含可结晶的聚乙烯链段，在内壳层中包含乙烯-丙烯无规共聚物的无定形聚合物，并且在外壳层中包含可结晶的聚丙烯链段。随着T _d的增加，从内壳到芯和外壳的软化和熔化发生。可以设想，橡胶颗粒内部不稳定区域的比例以及iPP基体与分散相之间的脱胶逐渐增加，从而为高腔体提供了更多的成核点T _d，因此观察到更强烈的空化。