聚對苯二甲酸丙酯結晶行為之研究

Abstract

聚對苯二甲酸丙酯（Polypropylene terephthalate, PPT）為一新的聚酯類結晶性材料。在本研究中利用了示差掃描式熱分析儀研究 PPT之結晶動力學。採用了等溫結晶以及非等溫結晶的方式來決定其 Avrami指數，根據 Avrami指數顯示 PPT其結晶化的過程包括了瞬間成核以及均相成核兩種機構的組合。並且以偏光顯微鏡觀察其結晶過程中的形態變化。 在等溫結晶過程以及之後的回火過程中，藉由其熔融行為的觀察，可得知 PPT的結晶微結構有明顯的變化。並且利用 Hoffman-Weeks 方程式可求得ppt的平衡熔點為 226℃ 。 PET, PPT以及PBT三者在結構上極為類似，在此利用了非等溫結晶的觀察，比較其結構對其結晶速率的影響。

Polypropylene terephthalate (PPT) is a newly developed crystalline polyester. This study utilized differential scanning calorimetry(DSC) to investigate the kinetics of PPT crystallization. The Avrami constant was determined by using both isothermal and non-isothermal crystallizations. Based on the obtained Avrami constant, the crystallization, mechanism of PPT includes instantaneous nucleation and homogeneous nucleation. Process of crystal growth was observed by using the polarized optical microscopy. During isothermal crystallization and annealing thereafter,the microstructure of crystals has been altered through observation of its melt behavior. The equilibrium melting temperature was determined at 226°C by means of Hoffman-Weeks equation. Three polyesters,PET, PPT, and PBT are structurally similar. We compare their relative relative rate of crystallization based on their difference in chemical structure. Transesterification occurs when polyesters are melt blended. The copolyesters from the transesterification tend to retard crystallization.Degree of transesterification of PPT/PET blend and is influence on crystallization behavior have been investigated.