Melt Temperature and Initial Polymorphs Dependencies of Polymorphs Selection during Subsequent Crystallization in Propylene-ethylene Random Copolymer

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• 作者：Jiayi Zhao ; Yingying Sun ; Yongfeng Men
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2017
• 出版时间：January 11, 2017
• 年：2017
• 卷：56
• 期：1
• 页码：198-205
• 全文大小：565K
• ISSN：1520-5045

文摘

Subsequent crystallization behavior during cooling for two random propylene-ethylene copolymers with 6 mol % ethylene co-units but different molecular weights initially in a pure α-form or pure γ-form processed at different melt temperatures was investigated using differential scanning calorimetry and wide-angle X-ray diffraction techniques. The onset crystallization temperature (T_onset) and fraction of the two polymorphs after crystallization depended on the molecular weight, initial polymorph, and melt temperature (T_melt). At high T_melt (120–160 °C), T_onset and the fraction of the γ-form (f_γ) increased with decreasing T_melt. For the high molecular weight sample initially in α-form, a higher T_onset and f_γ than the one in the γ-form was observed because a higher T_melt was needed to fully homogenize the melt for samples initially in the α-form due to the different morphology between the samples of different polymorphs. For the low molecular weight sample, the initial polymorph did not affect this process.