Crystallization of isotactic polypropylene under shear flow observed in a wide spatial scale

アイソタクチックポリプロピレンの流動場下での結晶化の広範囲な空間スケールにおける観察

荻野 慈子*; 福島 一*; 高橋 伸明; 松葉 豪*; 西田 幸次*; 金谷 利治*

Ogino, Yoshiko*; Fukushima, Hajime*; Takahashi, Nobuaki; Matsuba, Go*; Nishida, Koji*; Kanaya, Toshiji*

アイソタクチックポリプロピレン(iPP)の流動場における結晶化を時間分割広角X線(WAXS),小角X線(SAXS),偏光解消光散乱(DPLS),偏光光学顕微鏡(POM)測定により観察し、いわゆるシシ・ケバブ構造の形成過程を0.1nmから数十ミクロンに及ぶ広範囲な空間スケールにおいて研究した。時間分割DPLS, SAXS, WAXS測定からはシシ・ケバブそれぞれの結晶核形成,結晶成長過程が明らかとなった。また、結晶が異方的成長を示すひずみ速度の臨界値が存在することがわかった。実験結果を踏まえてシシ・ケバブ構造の形成過程の一つの可能性を提案した。

We studied crystallization process of isotactic polypropylene (iPP) under shear flow as a function of shear rate using time-resolved wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), depolarized light scattering (DPLS) and polarized optical microscope (POM) to elucidate the formation mechanism of the so-called shish-kebab structure in a wide spatial scale from 0.1 nm to several tens micro-m. In the time-resolved DPLS, SAXS and WAXS measurements we observed the formation processes of the shish-like structure, the kebab structure and the crystalline lattice (mostly in the kebab), respectively, and found that there were critical shear rates for the anisotropic structure formation in the DPLS, SAXS and WAXS measurements. The values are very close each other, suggesting the anisotropic structure formations in both of the shish and the kebab are dominated by a common origin. Furthermore, comparing the onset times of intensities in DPLS, SAXS and WAXS, we found that the onset of DPLS intensity is the most accelerated by the shear among the three. On the basis of the observations, we propose a possible mechanism for the shish-kebab structure.