Morphology and Growth of Single Crystals of Isotactic Polypropylene from the Melt |
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| Authors: | Koji Yamada Hiroshi Kajioka Koji Nozaki Akihiko Toda |
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| Affiliation: | 1. Kawasaki Development Center , SunAllomer Ltd. , Kawasaki-ku, Kawasaki, Japan;2. Graduate School of Integrated Arts and Sciences , Hiroshima University , Higashi-Hiroshima, Japan;3. Graduate School of Science and Engineering , Yamaguchi University , Yamaguchi, Japan |
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| Abstract: | Isolated single crystals of isotactic polypropylene (iPP) grown from the melt were studied by optical microscopy and atomic force microscopy (AFM). The single crystals had a well-known rectangular shape when crystallized at high temperatures (Tc) above 155°C. The width increased with decreasing Tc, and the shape became hexagonal below 130°C. The single crystals were sectored with thickness difference between them. The growth rate along the a*-axis, Ga*, agreed well with the growth rate of spherulites, as expected. Ga* had two inflection points on the plots against (TΔT)?1. The lower temperature inflection corresponds to the regime II-III transition, and the higher temperature one is accompanied by an inflection of the growth rate in the b-axis direction, Gb, which has been measured for the first time. The inflection of Gb at the lower inflection temperature of Ga* was much smaller than that of Ga* and may not exist. The crystals are basically surrounded with flat surfaces and no indications of kinetic roughening in the regime III were recognized in the AFM images. The inflections of Ga* and Gb caused a complicated shape change of the aspect ratio, having a minimum at around 135°C. |
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| Keywords: | growth rate isotactic polypropylene morphology single crystal |
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