The structural evolution of high-crystallinity polyglycolide (PGA) during hot-stretching from 50 °C to 150 °C was investigated using synchrotron in-situ WAXD/SAXS techniques. The structural evolution during stretching at different temperatures can be divided into three stages. The stage preceding the yield point, the lamellar crystals undergo extensive slip due to shear forces. The crystallite size decreases by 43.9 % during stretching at 50 °C, while it only decreases by 23.8 % at 150 °C. In this stage, cavities with their long axes vertical to the stretching direction form between the lamellar stacks parallel to the stretching direction. Higher stretching temperatures are less favorable for the formation of these cavities. Stage from yield point to onset of strain hardening, some of the small crystals formed in the previous stage accumulate in the oblique direction. After reaching the critical strain, they reorient towards the stretching direction. This reorientation causes fragmentation and recrystallization, promoting the further development of cavities. Both the cavities and the recrystallized crystals align along the stretching direction. In the strain-hardening stage, new crystal formation occurs under stress, and higher temperatures favor the formation of highly oriented crystals. As a result, the crystallinity and crystal orientation of PGA at the end of stretching are positively correlated with the stretching temperature.

中文翻译：

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可生物降解聚乙交酯中的晶体结构演化和空化：热拉伸过程中的原位 WAXD/SAXS 研究


使用同步加速器原位 WAXD/SAXS 技术研究了高结晶度聚乙交酯 (PGA) 在 50 °C 至 150 °C 热拉伸过程中的结构演化。不同温度拉伸过程中的结构演变可分为三个阶段。在屈服点之前的阶段，层状晶体由于剪切力而经历广泛的滑移。在 50 °C 拉伸过程中，微晶尺寸减小了 43.9%，而在 150 °C 拉伸时仅减小了 23.8%。在此阶段，在平行于拉伸方向的层状堆叠体之间形成长轴垂直于拉伸方向的空腔。较高的拉伸温度不太有利于这些空腔的形成。从屈服点到应变硬化开始的阶段，前一阶段形成的一些小晶体沿倾斜方向聚集。达到临界应变后，它们会重新定向到拉伸方向。这种重新取向导致碎裂和再结晶，促进空腔的进一步发展。空腔和重结晶晶体均沿拉伸方向排列。在应变硬化阶段，在应力作用下会形成新的晶体，较高的温度有利于形成高度取向的晶体。结果表明，拉伸结束时PGA的结晶度和晶体取向与拉伸温度呈正相关。