PET类共聚酯的玻璃化转变

用DSC,IR和DLI(解偏振光法)等方法研究了聚(对苯二甲酸/间苯二甲酸)乙二醇酯P(ET/EI)]和聚对苯二甲酸(乙二醇/丁二醇)酯P(ET/BT)]系列共聚酯的玻璃化转变.结果表明,共聚酯的玻璃化转变是玻璃态有序结构解序后的一种转变.随ET链段含量的减少,两系列共聚酯的玻璃化转变在DSC中均表现出由拐折渐变为峰形,这是由于需要维持构象转变的ET链段在数量上的减少所致.玻璃态共聚酯的有序结构与分子链末端的游离羟基有关,游离羟基与羰基形成氢键是PET及可结晶共聚酯在结晶时必须经历的一个过程,而不能结晶的共聚酯(IPA30)则因该氢键的形成导致其玻璃化转变的消失.

The Glass Transition of Copolyester

The glass transition of poly(ethylene tetrephthalate/isophthalate) and poly-(ethylene/teramethylene tetrephthalate) copolyesters were studied by using DSC,DLI (depolarized light intensity) and IR analysis. It was shown that the glass transition of copolyesters was a change after the disorientation of the order in their glassy state. The forms of glass transition in DSC thermograms of the two serial copolyesters transformed from step change to endothermic peak with the increase of ET segments in the molecular chains. This is caused by the decrease in the number of ET segments which need to maintain their conformation change. The order of glassy P(ET/EI) copolyester relates to the free hydroxy at the end of the chains. The formation of hydrogen bond between free hydroxy and carbonyl is a necessary process when PET and crystallizable copolyester crystallizing, and the glass transition of uncrystallizable copolyester(IPA 30) will disappear after the formation of these hydrogen bonds.