固态缩聚法改性聚对苯二甲酸丁二酯的反应动力学

The Reaction Kinetics of Modification of Poly(butylene terephthalate) via Solid State Polymerization

研究了芳香族二醇单体与聚对苯二甲酸丁二酯(PBT)的固态缩聚反应及其反应动力学.采用的二醇单体是对苯二甲酸二羟乙酯(BHET).一定配比的PBT和BHET混合物在185°C下进行固态缩聚(SSP)反应,分别利用凝胶色谱(SEC)、核磁共振氢谱(1H-NMR)和核磁共振碳谱(13C-NMR)对缩聚产物的数均分子量、分子结构进行了表征.SEC表征的结果表明:反应起始阶段聚合物的数均分子量快速下降,这是由于酯交换导致PBT链的断裂,形成了低聚物;0.5 h后,所有自由的BHET单体都已参与了酯交换反应;此后,所得到的低聚物重新缩聚,导致数均分子量上升,最终得到高数均分子量共聚物.1H-NMR表征结果表明,随着固相反应的进行乙二醇基团在体系中趋于无规分布.13C-NMR表征结果表明:在反应起始阶段,体系自由度快速上升;反应4 h后,自由度开始趋于缓和,所得共聚物的化学结构趋于稳定.

The kinetics of the solid-state polymerization （SSP） of 2-（hydroxyethylterephthalate） （BHET） in poly（butylene terephthalate） （PBT） was studied. The 70 ： 30 mol% PBT ： BHET mixtures were polymerized via SSP at a reaction temperature of 185 ℃ while the reaction time was varied. The SEC results show that the molecular weight decreases during the initial stage of SSP reaction, due to the scission of PBT chains. During the first half hour, almost all of the free BHET monomers are polymerized. After that, the polymer chains start to recombine and result in the increasing of molecular weight. Consequently, high molecular weight final products are obtained. The 1^H-NMR sequence distribution analysis indicates that the distribution of ethylene glycol units （EG） become increasingly random as the reaction processing. The degree of randomness （R） of copolymer is calculated from 13^C-NMR results. R starts with a value below 1, and increases dramatically in the initial stage of SSP reaction. It levels off after tSSP =4 h, which indicates the stabilization of copolymer＇s chemical structure.