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Further study on double-melting endotherms of isotactic polypropylene

机译：等规聚丙烯双熔融吸热的进一步研究

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The origins of the single- and double-melting endotherms of isotactic polypropylene crystallized at different temperatures were studied carefully by differential scanning calorimetry, wide-angle X-ray diffraction, and small-angle X-ray scattering. The experimental data show that spontaneous crystallization occurs when the crystallization temperature is lower than 117 degrees C; thus the lamellae formed are imperfect. At a lower heating rate, the recrystallization or reorganization of these imperfect lamellae leads to double endotherms. On the other hand, when the crystallization temperature is higher than 136 degrees C, two major kinds of lamellae with different thickness are developed during the isothermal process, which also results in the double-melting endotherms. In the intermediate temperature range the lamellae formed are perfect, and there is only a single peak in the distribution of lamellar thickness. This explains the origin of the single-melting endotherm. (C) 2000 John Wiley & Sons, Inc. [References: 29]
机译：通过差示扫描量热法，广角X射线衍射和小角X射线散射，仔细研究了在不同温度下结晶的等规聚丙烯单熔融和双熔融吸热的起源。实验数据表明，当结晶温度低于117℃时，发生自发结晶。因此形成的薄片是不完美的。在较低的加热速率下，这些不完美薄片的重结晶或重组导致了双重吸热。另一方面，当结晶温度高于136℃时，在等温过程中会产生两种厚度不同的主要薄片，这也导致了两次熔化的吸热。在中间温度范围内，形成的薄片是完美的，并且在薄片厚度的分布中仅存在一个峰。这解释了单熔化吸热的起源。 （C）2000 John Wiley＆Sons，Inc. [参考：29]

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