PET固相缩聚前后的结晶行为

聚对苯二甲酸乙二酯(PET)固相缩聚过程存在聚合反应与结晶偶合的现象。利用自制的固相缩聚实验装置结合差示扫描量热法(DSC)对PET固相缩聚反应中的结晶行为进行了研究。结果表明:DSC升温速率增加使PET冷结晶峰温度明显升高,结晶峰面积减小,而熔融峰温度和面积随升温速率的变化很小;等温结晶时不同结晶温度的结晶形态存在差异,结晶形态取决于温度和结晶历史;PET固相缩聚过程中结晶度随反应温度和反应时间的增加而增加,并且缩聚反应的进程促进新结晶体的生成。

Crystallization Behavior of Poly(ethylene terephthalate) before and after Solid State Polycondensation

There is an interference effect between reaction and crystallization in solid state polycondensation(SSP) of poly(ethylene terephthalate)(PET).The crystallization behavior of PET with SSP was investigated using self-made oil-both reactor and differential scanning calorimetry(DSC).The crystallization temperature of the peak for PET pellets is higher and the enthalpy is smaller as the DSC heating rate increases.The results indicate that there is the melting-recrystallization-remelting process for PET at low DSC heating rate.The imperfect crystallites formed at lower crystal temperature.The crystallization structure has been observed by Nikon E600 polarizing microscope(with heating and freezing stage).The fractional crystallinity increases as the increase of the SSP temperature and reaction extent.There is a new crystal formation with the development of solid state polycondensation for PET pellets.