聚對苯二甲酸乙酯與POB/PET共聚酯之聚摻合研究

Abstract

PET的結晶速率慢，因此不能用於如射出成型的高速率加工工程上。在 PET內摻入高分子成核劑可以提高其結晶速率。一系列不同組成的POB/PET 共聚酯如P28、P46、P64和P82，將由聚對苯二甲酸乙酯(Polyethylene Terephthalate, 簡稱PET)與對羧基苯甲酸(p-acetoxybenzoic acid, 簡稱 PAB)聚縮合反應 (polycondensation)而成。PET再與1 ~ 50 wt % 的共聚 酯進行聚摻合。 利用微差掃描式熱分析儀(DSC)及偏光顯微鏡來研究PET摻合物的結晶 行為。結果顯示，摻入15 wt % 以下的共聚酯可提高PET的結晶速率，又以 摻合10 wt % P28的效果最顯著，由POM的研究亦獲得相同的結果。 由掃描式電子顯微鏡(SEM)的觀察得知，所有PET摻合物皆為兩相系統， 共聚酯的組成與PET越相近，兩相間的相容性和黏著性越好。由氫核磁共振 光譜儀(proton NMR)的分析，確認有酯交換反應的發生。酯交換造成PET熔 點、熔化熱、結晶溫度和結晶熱的降低。酯交換程度隨著摻合時間的增加 而增加，而酯交換反應速率常數k的大小與酯交換溫度、共聚酯的組成及含 量有關。另一方面，酯交換可 改善兩相間的相容性。 Polyethylene terephthalate (PET) has not been considered for application involving high-speed processing such as injection molding because it crystallizes or solidifies very slowly from melt. Crystallization can be increased by the addition of polymeric nucleating agent. A series of co[poly(ethylene terephthalate-p-oxybenzoate)] copolyester, designated P28, P46, P64, and P82, were synthesized from various ratios of two different moieties of either poly(ethylene terephthalate) with p-acetoxybenzoic acid through polycondensation process. PET was melt-blended with these copolyesters in the range of 1 ~ 50 wt %. The crystallization behavior of blends were then studied by DSC and polarizing optical microscope (POM). Crystallization rate and crystallization temperature of PET are increased for blends consisting of less than 15 wt % of copolyesters. The significantest acceleration of crystallization rate is at 10 wt % P28. The fact was more confirmed by the photomicrographs obtained from cooling cycle. Two-phase morphology was observed by scanning electron microscopy (SEM) micrographs in all the blends. It was observed that the more similar the composition between the copolyester and PET in the blends is the better the miscibility or interfacial adhesion between the two phases. The transesterification detected by proton NMR analysis occur during the processing at a greater level if the blending time increases. These interchange reactions hinder the crystallization processes of PET and result in a decrease of the melting point, the heat of fusion, crystallization temperature and the heat of crystallization of the neat PET. On the other hand, the miscibility between the two phases can be improved owing to the transesterification. The transesterification rate constant k is as a function of the reaction temperature, the composition of copolyester and the content of copolyester in the blend.