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用升温在位偏振红外光谱测量方法，研究了不同取向态的聚对苯二甲酸乙二酯（ＰＥＴ）膜在热弛豫过程中的尺寸变化以及分子链构象和取向的变化．结果说明，ＰＥＴ小尺度取向链段的热弛豫较大尺度取向分子链的热弛豫在较低的温度下发生，取向ＰＥＴ膜的热收缩主要与分子链大尺度取向的弛豫有关，而其后的自发伸长是结晶过程引起的，分子链的取向程度对结晶伸长的幅度有着重要影响．
The changes in the dimensional changes and the conformations and orientations of polyethylene terephthalate (PET) films with different orientation states during thermal relaxation were studied by the method of temperature-rising in situ polarized infrared spectroscopy. The results show that the thermal relaxation of PET oriented small-scale segments is related to the thermal relaxation of larger-scale oriented molecular chains at lower temperatures. The thermal contraction of oriented PET films is mainly related to the relaxation of large scale oriented molecular chains. The subsequent spontaneous elongation is caused by the crystallization process, and the degree of orientation of the molecular chains has an important influence on the magnitude of the crystal elongation.