ABSTRACT Semi-crystalline polymers are observed to change their mechanical properties upon processing due to the changes in the crystallinity of the polymer. This paper investigates the changes in the crystallinity and mechanical properties of biaxially stretched polyethylene terephthalate, PET, for different stretch ratios (or strains). Each stretched PET sample was heated to 100°C in a biaxial stretching machine before being stretched to the desired stretch ratio. The same strain rate of 2/s was used for the stretching and mode of deformation was simultaneous on either side. Differential Scanning Calorimetry (DSC) was used to investigate the variation of induced crystallinity with stretch ratio. Tensile tests were used to determine the variation of the processing stretch ratios with mechanical properties. The results show that the higher the stretch ratio, the higher the amount of induced crystallinity in the PET sample. Also, the higher the stretch ratio, the better the mechanical properties.

中文翻译：

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拉伸比对双轴拉伸PET诱导结晶度和力学性能的影响

摘要 由于聚合物结晶度的变化，观察到半结晶聚合物在加工过程中会改变其机械性能。本文研究了双轴拉伸聚对苯二甲酸乙二醇酯 (PET) 在不同拉伸比（或应变）下结晶度和机械性能的变化。每个拉伸的 PET 样品在拉伸至所需拉伸比之前在双轴拉伸机中加热至 100°C。拉伸使用相同的应变速率 2/s，变形模式在两侧同时进行。差示扫描量热法 (DSC) 用于研究诱导结晶度随拉伸比的变化。拉伸试验用于确定加工拉伸比随机械性能的变化。结果表明拉伸比越高，PET样品中的诱导结晶量越高。此外，拉伸比越高，机械性能越好。