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α’-晶型聚乳酸(PLA)膜被制备和单轴拉伸.通过凝胶渗透色谱仪(GPC)、全反射红外光谱(ATR-IR)、差示扫描量热仪(DSC),X射线衍射(XRD)及Raman光谱等测试技术研究了拉伸温度梯度变化对α’-晶型PLA膜的分子量及其分布、分子链构象、结晶度、晶型转变和取向行为的影响.在恒定拉伸速度与应变下,拉伸温度对PLA膜的应力-应变曲线,特别是屈服强度、拉伸模量产生了较大的影响,其值随拉伸温度的增加而降低.GPC测试结果表明,在不同的温度下拉伸后,PLA会发生一定程度的降解,分子量降低;ATR-IR,XRD,DSC和Raman光谱测试结果表明,在不同的温度下拉伸后α’-型PLA没有发生晶型的转变,即没有由α’-晶体转变为α-或β-晶体.结果表明PLA的结晶度、分子链取向程度强烈依赖于拉伸温度:当拉伸温度低于100℃时,α’-型PLA膜的结晶度与沿着拉伸方向的变形程度随拉伸温度的增加而增加,分子链的高度取向诱导了PLA结晶;当拉伸温度超过100℃后,PLA的分子链沿着拉伸方向上的有序度与结晶度将降低.
α’-Crystalline Polylactic Acid (PLA) film was prepared and uniaxially stretched by gel permeation chromatography (GPC), total reflection infrared spectroscopy (ATR-IR), differential scanning calorimeter (DSC), X Ray diffraction (XRD) and Raman spectroscopy were used to investigate the effect of temperature gradient on the molecular weight, distribution, molecular chain conformation, crystallinity, crystal transition and orientation of α’-PLA film. At tensile speed and strain, the tensile temperature has a significant effect on the stress-strain curve, especially the yield strength and tensile modulus of PLA films, and its value decreases with the increase of stretching temperature.The results of GPC test , The PLA will degrade to a certain extent after being stretched at different temperatures, and the molecular weight decreases. The results of ATR-IR, XRD, DSC and Raman spectroscopy show that the α’-PLA did not occur after stretching at different temperatures The change of the crystal form, that is, the transition from α’-to α-or β-crystal, shows that the degree of crystallinity and molecular orientation of PLA strongly depends on the stretching temperature: when the stretching temperature is below 100 ℃, α ’- PLA film, the degree of crystallinity along the stretching direction and the degree of deformation increases with the increase of stretching temperature, the molecular chain The high degree of orientation induced the crystallization of PLA. When the stretching temperature exceeded 100 ℃, the degree of ordering and the degree of crystallinity along the stretching direction of the molecular chain of PLA decreased.