Low-modulus polypropylene (LMPP) with controlled stereoregularity was prepared based on the original catalyst technology [Minami et al. (Polym J 47:227–34, 2015)]. The LMPP showed elastic recovery, while plastic deformation was dominant in isotactic polypropylene. To understand the underlying mechanism, changes in the morphology of LMPP under cyclic uniaxial elongation were investigated using in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). During the first cycle, yielding appeared in the stress–strain (S–S) curve, and the residual strain was large. The SAXS pattern is a ring pattern at strain zero and then changes to a four-point pattern and a two-point pattern with increasing strain. This four-point pattern is derived from the undulating structure of the crystal lamellae. During the stretching process, this undulation is large, and fragmentation of the lamellae occurs. Therefore, the residual strain increases. During the second cycle, no yield appeared in the S–S curve, and the residual strain was small. The SAXS pattern changed quickly from a four-point pattern to a two-point pattern. This result suggests that little fragmentation of the lamellae occurs and that only the lamellae were rotating under elongation. Thus, plastic deformation hardly occurs, and the residual strain decreases. Based on these results, lamella fragmentation has a significant effect on the elastic-recovery rate. Low-modulus polypropylene (LMPP) with controlled stereoregularity showed elastic recovery. To understand the underlying mechanism, changes in the morphology of LMPP under cyclic uniaxial elongation were investigated using in situ SAXS and WAXD. During the first cycle, the undulating structure of the crystal lamellae is large, and fragmentation of the lamellae occurs. On the other hand, during the second cycle, the little fragmentation of the lamellae occurs and that only the lamellae were rotating under elongation. Based on these results, lamella fragmentation has a significant effect on the elastic-recovery rate.

中文翻译：

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单轴循环拉伸下低模量聚丙烯形貌变化的X射线散射研究

基于原始催化剂技术制备了具有可控立构规整性的低模量聚丙烯 (LMPP) [Minami et al. (Polym J 47:227–34, 2015)]。LMPP 表现出弹性恢复，而塑性变形在等规聚丙烯中占主导地位。为了了解其潜在机制，使用原位小角 X 射线散射 (SAXS) 和广角 X 射线衍射 (WAXD) 研究了循环单轴拉伸下 LMPP 形态的变化。在第一个循环中，应力-应变（S-S）曲线出现屈服，残余应变较大。SAXS 模式是应变为零时的环形模式，然后随着应变的增加变为四点模式和两点模式。这种四点图案源自水晶薄片的起伏结构。在拉伸过程中，这种起伏很大，发生薄片破碎。因此，残余应变增加。在第二个循环中，S-S曲线没有出现屈服，残余应变很小。SAXS 模式从四点模式迅速转变为两点模式。该结果表明薄片很少发生碎裂，并且只有薄片在伸长下旋转。因此，几乎不发生塑性变形，残余应变减小。基于这些结果，薄片破碎对弹性恢复率有显着影响。具有受控立构规整性的低模量聚丙烯 (LMPP) 显示出弹性恢复。为了了解其潜在机制，使用原位 SAXS 和 WAXD 研究了循环单轴拉伸下 LMPP 形态的变化。在第一个循环中，晶体片晶的起伏结构较大，片晶发生碎裂。另一方面，在第二个循环中，薄片发生了很小的碎裂，并且只有薄片在伸长下旋转。基于这些结果，薄片破碎对弹性恢复率有显着影响。