Temperature Dependence of Crystal Growth Rate for α and β Forms of Isotactic Polypropylene
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In this paper, the growth rate of the α1, α2 and β forms of isotactic polypropylene (iPP) and their morphological changes were studied in a wide range of crystallization temperatures.Abstract:
The crystal growth rate of the α1, α2 and β forms of isotactic polypropylene (iPP) and their morphological changes were studied in a wide range of crystallization temperatures. The temperature dependence of the crystal growth rate of the α1 form showed a bell-shaped curve with the maximum growth rate (Gmax) at 70 °C. The crystal growth rate of the β form induced by calcium pimelate also showed a bell-shaped curve with Gmax at 79 °C. Two crossover points on the growth rate curve from the α1 form to the β form or vice versa were observed at 90 °C and 133 °C, respectively. Tear-drop shaped spherulites were observed at temperatures between the two crossover points. Electron diffraction patterns showed the high ordered structure of the α2 form for thin films crystallized at 140 °C. The α2 fraction became detectable in X-ray diffraction pattern for temperatures above 110 °C. The α2 fraction increased with crystallization temperature and saturated to 100% at about 140 °C. In the temperature region from 110 °C to 140 °C, several crystal growth rates were found at the same crystallization temperature. The growth rate variations could be associated with the co-crystallization of the α1 and α2 forms. Above 140 °C, the growth rate variations disappeared, since the fraction of the α2 reached to 100%. The extrapolated Gmax of the α2 showed at 72 °C.read more
Citations
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Molecular Ordering and Molecular Dynamics in Isotactic-Polypropylene Characterized by Solid State NMR
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Crystal Polymorphism and Morphology of Polylactides
TL;DR: The crystal structures of poly(l-lactic acid) (PLLA), its stereocomplexes, and some features of its crystallization process are reviewed in this article, where a number of unusual crystallization features (increased growth rate, thicker lamellae, structural disorder) are reviewed.
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Extensional Flow-Induced Dynamic Phase Transitions in Isotactic Polypropylene.
Jianzhu Ju,Zhen Wang,Fengmei Su,Youxin Ji,Haoran Yang,Jiarui Chang,Sarmad A Ali,Xiangyang Li,Liangbin Li +8 more
TL;DR: The violent competitions among four phases near the boundary of crystal-melt may frustrate crystallization and result in the non-crystalline shish winning out.
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Temperature‐dependent selective crystallization behavior of isotactic polypropylene with a β‐nucleating agent
Ziwei Cai,Yao Zhang,Jingqing Li,Yingrui Shang,Hong Huo,Jiachun Feng,Sérgio S. Funari,Shichun Jiang +7 more
TL;DR: In this article, the authors investigated the crystallization behavior of isotactic polypropylene (iPP) induced with various concentrations of the β-form nucleating agent aryl amide derivative (TMB-5) at different temperatures.
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Solid-State NMR Characterization of the Chemical Defects and Physical Disorders in α Form of Isotactic Poly(propylene) Synthesized by Ziegler−Natta Catalysts
TL;DR: In this article, the order-disorder phenomenon and spatial heterogeneity of chain packing, partitions of stereodefects, and molecular dynamics of α form of isotactic polypropylene (iPP) samples, which are synthesized by Zieglar-Natta catalysts, are investigated by solid-state (SS) NMR.
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TL;DR: A survey of spherulites formed by the isothermal crystallization of polypropylene from the melt in the temperature range 110°−148°C is given in this paper. But their structural morphology, optical properties, melting behavior, and growth rates have not been examined.