【作者】 王嫄；

【导师】 李光；

【作者基本信息】 东华大学 ， 高分子化学与物理， 2008， 硕士

【摘要】 本文以对苯二甲酸（PTA）、乙二醇（EG）以及1,4-环己烷二甲醇（CHDM）为原料,采用直接酯化法合成了一系列不同配比的PET-PCT共聚酯。此外,还以3～5mol%的5-磺酸钠-1,3-间苯二甲酸二甲酯（SIPM）取代部分对苯二甲酸二甲酯（DMT）与EG及CHDM进行反应的基础上,以酯交换法制得了一组不同离子基团含量的PET-PCT离聚物（SPET-PCT）,其中CHDM的添加量为10mol%。采用核磁共振技术对PET-PCT共聚酯的分子结构进行了分析,结果表明产物为无规嵌段共聚酯,共聚酯中PCT链段的实际含量大于CHDM/EG的投料比,共聚酯中PET链段和PCT链段的平均序列长度与其含量成正比。SPET-PCT的红外光谱在628cm^-1处存在的C-S键伸缩振动峰表明离子基团被成功引入到共聚物大分子链上。利用差示扫描量热仪（DSC）分析了共聚酯的热性能。随CHDM含量的增加,共聚酯的结晶能力下降,CHDM的加入量至15mol%时已基本可以获得非晶共聚酯;PET-PCT共聚酯的玻璃化转变随CHDM的增加向高温移动;PCT链节含量低的样品在退火后于低温处和高温处出现了两个熔融吸热峰,且Tm和△Hm随PCT含量的增加而降低。因此,可以通过控制EG/CHDM的比例制备不同结晶程度乃至非晶的共聚酯。对于SPET-PCT,无论热处理与否均未出现熔点,说明此离聚物是非晶态的。广角X-射线衍射的结果也进一步证明在CHDM含量较低的情况下,共聚酯可以结晶且结晶衍射峰与PET一致,随CHDM含量的增加,共聚物变为非晶态;SPET-PCT没有显示结晶衍射峰,与DSC及偏光显微镜观察的结果一致。用密度梯度法测试了共聚酯及其离聚物的密度,发现随CHDM含量增加,PET-PCT共聚酯的密度逐渐变小;SPET-PCT的密度小于相应的PET-PCT的密度值。对共聚酯不同升温速率的热失重（TG）分析表明,在N₂气氛中共聚酯具有良好的热分解稳定性,所有样品的起始分解温度大于400℃,最大分解温度均大于435℃。用Friedman法对共聚酯的热分解动力学分析表明:与PET相比,PET-PCT共聚酯的E值、n值有所降低,但各共聚酯间的E值、n值差别不大,这表明在CHDM含量较少的范围内,CHDM对共聚酯的热稳定性影响不大。对离聚物的TG分析表明,离子基团的引入使共聚酯的热稳定性稍有下降。对共聚酯及其离聚物的裂解-气相色谱-质谱的分析表明在不同的裂解温度下,产物的组成差别很大。在550℃裂解时,在总离子流图上的各特征裂解产物明显,为PET-PCT共聚酯及其离聚物的结构鉴定提供了丰富的信息。采用高级转矩流变仪（ARES-RFS）和动态力学分析仪（DMA）研究PET-PCT共聚酯及其离聚物的微观相态结构。动态流变测试表明G’～freq曲线出现明显的末端区效应,随PCT含量的增加G’偏离线性关系的频率移向高频;动态力学性能测试发现DMA图谱中tand曲线上显示出两个玻璃化转变峰,且即使试样经充分热定型处理后仍呈现双玻璃化转变,由此证明PET-PCT共聚酯呈现微相分离相态结构特征。更多还原

【Abstract】 A series of poly（ethylene-co-1,4-cyclohexylenedimethylene terephthalate） copolymers （PET-PCTs） were prepared through direct esterification technique from terephthalic acid, ethylene glycol （EG） and 1,4-cyclohexane dimethanol （CHDM）. Furthermore, two sulfonated PET-PCTs （SPET-PCTs） containing ionic groups were prepared via interchange esterification from dimethyl terephalate （DMT）, 5-sulfoisophthalate’ sodium salt （3～5mol%, with respect to DMT）, EG and 10mol% of CHDM.The chemical composition and sequence length distribution of the copolyesters were investigated by means of ¹H-NMR and ¹³C-NMR. The results demonstrated that PET-PCTs were random block copolyesters and the content ratio of PCT/PET was always greater than the loading ratio of CHDM/EG, moreover, the number-average sequence length of each kind of block was in proportion to its content in the copolymer. SPET-PCT samples were analyzed via FT-IR, the appearance of absorption peak located at 628cm^-1, which was characteristic of the stretching vibrations of C-S bond, confirmed that the ionic group -SO₃Na had been chemically linked in the polymer chains.The crystallization behavior of the copolyesters was studied by means of DSC. It was found that the glass transition temperature（Tg） of PET-PCT increased with the increasing content of PCT units, non-crystallization polymer would be obtained when the CHDM content reached to 15mol%. On the other hand, the annealed samples with low PCT content showed two melting temperatures（Tm） within the low and high temperature region respectively, furthermore, the values of Tm and melting enthalpy decreased with the content of PCT units. Therefore, copolyesters with different crystallinities or even the amorphous products could be obtained by controlling the loading ration of EG/CHDM. Concerning the SPET-PCT samples, no melting points have been found in their DSC curves, indicating that those ionomers were amorphous.The WXRD results showed that with the low content of CHDM, the copolyester possessed a similar crystalline diffraction to that of PET, and then gradually became amorphous with the increasing of CHDM content. However, SPET-PCTs never showed crystalline diffraction peaks. These results were all in concordance with those of DSC and POM.The densities of PET-PCTs and SPET-PCTs were measured in a density gradient column. The density of PET-PCT decreased with the increscent content of CHDM while the density of ionomer was lower than that of PET-PCT with a same CHDM content. TGA showed that PET-PCTs possessed an excellent thermal stability, i.e., the onset degradation temperatures were higher than 400℃and the temperature of the maximum weight loss rate were higher than 435℃. The analysis on thermal decomposition kinetics of PET-PCTs has also been performed with Friedman method, the activation energy and the reactive constant of thermal degradation of PET-PCT decreased slightly in contrast with PET, so did the ionomers. However, the thermal stability difference between any copolyester was little.Pyrolysis gas chromatograph-mass spectrogram has been used to investigate of pyrolysates of the copolymers. It has been found the components of pyrolysate were rather different under various temperatures. Especially, the characteristic pyrolysate products were distinct, affording rich information to identify the structure of those copolymers.The micro-phase structures of copolymers have been investigated by using dynamic rheology measurement （ARES-RFS） and dynamic mechanical analysis （DMA）. A divergence from the linear relationship between storage modulus（G’） and frequency（freq） has been found within the low freq region, and this terminal region effect would shift to higher freq region with the increasing content of PCT in the copolymers. Moreover, two Tg’s have been observed from DMA curves for the samples soever annealed or not. Therefore, it could be concluded that the micro-phase separation had taken place in PET-PCT copolyesters.更多还原