PET固相缩聚进展

固相缩聚是20世纪60年代开始发展起来的新型缩聚反应方式,有利于降低反应过程中的降解反应和副反应;对常规聚对苯二甲酸乙二醇酯(PET)切片进行固相缩聚处理可以大幅提高PET分子量,其产品的性能得到较大幅度的提升。文中首先对PET固相缩聚的反应过程、速度控制等反应机理进行了介绍,然后从原料粒子内部和外部两方面对PET固相缩聚反应的影响因素进行了分析,最后指出PET固相缩聚目前的研究情况和研究趋势。     

固相缩聚与PET的熔融性能

应用差示扫描量热法（ＤＳＣ）和广角Ｘ射结衍射（ＷＡＸＤ）研究了低温干燥高温固相缩聚ＰＥＴ的熔融行为和结晶结构。根据ＤＳＣ结果分析了固相缩聚反应温度和时间对熔融双峰的影响,得到熔点与固相缩聚反应温度有红性关系,熔点和结晶度与固相缩聚反应时间的对数呈线性关系。利用ＷＡＸＤ研究了固相缩聚反应温度和时间对表观晶粒尺寸的影响。结果说明低温结晶时形成的不完善晶体在固相缩聚过程中发生部分熔融、重结晶,结晶结构趋     

固相缩聚与PET的熔融性能

应用差示扫描量热法（ＤＳＣ）和广角Ｘ射线衍射（ＷＡＸＤ）研究了低温干燥高温固相缩聚ＰＥＴ的熔融行为和结晶结构。根据ＤＳＣ结果分析了固相缩聚反应温度和时间对熔融双峰的影响,得到熔点与固相缩聚反应温度有线性关系,熔点和结晶度与相缩聚反应时间的对数呈线性关系。利用ＷＡＸＤ研究了固相缩聚反应温度和时间对表观晶粒尺寸的影响。结果说明低温结晶时形成的不完善晶体在固体缩聚过程中发生部分熔融、重结晶,结晶结构趋于     

聚酯－聚醚嵌段共聚物的合成及抗静电性能研究

研究和分析了ＰＥＧ分子量、加料次序、反应时间和温度、物料比例、分散剂和固相缩聚等因素对ＰＥＴ－ＰＥＧ嵌段共聚物分子量和耐水性的影响。合成的嵌段共聚酯醚与ＰＥＴ共混纺丝可以显著改善ＰＥＴ纤维的抗静电性能。     

聚酯—聚醚嵌段共聚物的合成及抗静电性能研究

研究和分析了ＰＥＧ分子量、加料次序、反应时间和温度、物料比例、分散剂和固相缩聚等因素对ＰＥＴ－ＰＥＧ嵌段共聚物分子量和耐水性的影响。合成的嵌段共聚酯醚与ＰＥＴ共混纺丝可以显著改善ＰＥＴ纤维的抗静电性能。     

含介晶基因的半刚性共聚酯的合成及其性能研究

通过介晶单体４,４’联苯分别与对苯二甲酰氯及４,４’（对苯二甲酰氧基）二苯甲酰氯进行高温溶液缩聚反应合成了两种含介晶基团的半刚性共聚酯ＢＨＨＢＰ／ＴＰＣ与ＢＨＨＢＰ／ＴＯＢＣ。利用ＤＳＣ、ＴＧ－ＤＴＡ、偏光显微镜和Ｘ射线衍射等手段对介晶体ＢＨＨＢＰ与共酯的相变行为以及共聚酯的热分解动力学及结晶性能进行了研究。结果表明,两共聚酯均为结晶性聚合物,其中ＢＨＨＢＰ／ＴＯＢＣ具有向列相液晶相存在;共聚酯Ｂ     

制备新型相容剂——聚丙烯固相接枝苯乙烯的研究

用固相接枝共聚方法制备聚丙烯接枝苯乙烯共聚物（ＰＰ－ｇ－ＰＳ），详细考察了聚丙烯与引发剂的品种、反应温度、苯乙烯与引发剂的浓度等地接枝率的影响。结果表明，ＰＰ－ｇ－ＰＳ具有较高的接枝率。共聚ＰＰＪ３４０与ＰＰ粉接枝率均较均聚ＰＰＦ４０１为高；将３种引发剂（ＢＰＯ、ＴＢＰ、ＤＣＰ）进行比较在相同的下，以ＴＢＰ作为引发剂的接枝率最高；接枝率随ＳＴ／ＰＰ质量比增大与反庆温度的提高而提高。将ＰＰ－ｇ－ＰＳ     

固相缩聚共聚酯的熔融行为和结晶速率研究

通过固相缩聚合成了两种不同结构的高分子量共聚酯，研究了样品的熔融行为和结晶速率。研究发现，共聚酯的熔融峰随着固相聚合温度和时间的变化而与纯ＰＥＴ有明显的差别，共聚酯泊结晶速率与慢于纯ＰＥＴ的结晶速率。     

PET的燃烧及阻燃机理研究

本研究通过对纯ＰＥＴ及添加不同阻燃剂的ＰＥＴ样品燃烧的气相、固化产物的红餐光谱和ＣＯＮＥ实验分析,探讨了ＰＥＴ的燃烧阻燃机理。认为ＰＥＴ燃烧时,在生成气相产物的同时,还会发生交联反应形成环烯结构。溴化磷酸酯阻燃剂具有磷、溴协同效应,可在气相到固相全过程内起阻燃作用;而芳香族溴化物主要是气相阻燃机理;聚合型溴化聚芳烃,由于聚合聚合物链可能参与ＰＥＴ降解过程的交联反应,所以也是气相、固相均有阻燃作用。     

PEG分子量对PET-PEG共聚物结晶性能的影响

通过共缩聚反应合成了不同ＰＥＧ分子量的ＰＥＴ－ＰＥＧ共聚物，其中ＰＥＧ含量占７％（相对于ＤＭＴ质量比），以ＤＳＣ、解偏振光法测定了共聚物的结晶性能和结晶速度。结果表明ＰＥＧ的引入能有效地增加分子链柔性，改善结晶性能，尤其ＰＥＧ分子量为４０００时，结晶速度得以大大提高，温度为１１０℃时，ＰＥＴ－ＰＥＧ４０００结晶速度仅１ｍｉｎ，电镜分析表明共聚物中的ＰＥＧ分子量提高有助于分子链的有序性提高，从而加速结晶，但同时也会引起分子链缠结，从Ｘ衍射图谱上，可以看出ＰＥＧ在结晶过程中并不进入ＰＥＴ晶格中，它只起到诱导结晶的作用。     

聚对苯二甲酸丁二醇酯的固相缩聚

分子量对聚对苯二甲酸丁二醇酯 (PBT)的性能有直接影响 ,高分子量PBT通常经固相缩聚的方法获得。本文对PBT固相缩聚的机理、影响因素及产物的结晶和熔融性能进行了全面介绍     

Mechanical properties and reactions of PBT/PTW blends

The new rubbery poly(ethylene-butylacrylate-glycidyl methacrylate) (PTW) containing epoxy groups was used as a toughener for poly(butylene terephthalate) (PBT). The morphology and mechanical property of the PBT/PTW blend was studied. The reactions between PBT and PTW resulted in improvement of toughness, and were affected by the content of PTW. The reaction during the blending process was followed using an internal mixer. The simulated interfacial reaction between PBT and PTW was studied using the ARES rheometer. The complex viscosity curve could be divided into three stages to characterize the interfacial reactions between PBT and PTW at different temperatures. The temperature strongly affected the rates of the interfacial reaction and diffusion. The reaction of the mixture of PBT and PTW in the internal mixer was much faster than that at the simulated interfacial region. Finally, the differences between the simulated interfacial reaction and the reaction during the real processing were discussed.     

利用残缺样本声速重构声速剖面

用经验正交函数(experiential orthogonal functions,EOF)表示声速剖面受限于样本声速的测量深度,应用该方法重构声速剖面只能计算到样本中最浅剖面的深度。要想进行全海深声速剖面的重构,必须对残缺的样本声速进行合理地外延。为此,首先对样本中温度和盐度进行了外延,然后根据声速经验公式计算得到了全海深的样本声速。在此基础上,通过解多元方程组的办法求解经验正交函数系数达到了声速剖面重构的目的。结果表明,提出的声速剖面外延方法是有效的。另外,只要知道声速剖面变化较剧烈深度上的3个点的声速值就能重构声速剖面,对于文中的数据来说,重构的均方根误差可达到0.872 m/s;增加经验正交函数的阶数能提高重构精度,但5阶以上,阶数的继续增加对精度的提高将不会有显著的影响。     

ZrO2-C-ZrB2复合材料的氧化动力学

通过差热-热重分析研究了ZrB₂含量为10 %的ZrO₂-C-ZrB₂复合材料在800～1100℃下空气中的氧化动力学,根据气固相反应原理建立氧化动力学模型,计算反应表观活化能,并得到氧化速率与温度的经验关系式。结果表明,试样在 800℃时的氧化过程仅有化学反应控速阶段与化学反应和气体扩散共同作用的混合控速阶段。900～1100℃的氧化过程为前期是化学反应控速阶段,中期为混合控速阶段,后期为扩散控速阶段。三个阶段的表观活化能分别为111.7、71.5和166.0kJ·mol-1 。材料等温氧化的质量变化规律表明在900℃～1100℃内的氧化属于保护型氧化。     

Degradation and calcification of a PEO/PBT copolymer series

In this study the influence of polyethylene oxide content (70, 60, 55, 40 and 30%) on degradation and calcification of dense polyethylene oxide (PEO)/polybutyleneterephthalate (PBT) copolymer cylinders was evaluated at subcutaneous sites in goats. Histologically, the 30/70 and 40/60 PEO/PBT implants revealed no signs of calcification and of degradation, although slight surface alterations were evident after 1 year. In contrast, peripheral fragmentation and intermediate calcification were observed for 55/45 and 60/40 PEO/PBT specimens. After subsidence of the inflammatory reaction to the surgical intervention, the tissue reaction to these four PEO/PBT proportions was characterized by a fibrous capsule, although macrophages were frequently seen bordering 55/45 and 60/40 fragments. More extensive degradation and calcification were encountered for 70/30 PEO/PBT samples. Peripheral crack formation occurred from 4 weeks on and at 12 weeks, surface fragmentation was observed for this material. Fragments were usually surrounded by macrophages and, in addition, phagocytes with a foamy appearance were found. Fragmentation and phagocytotic activity increased during the course of the experiment. Using confocal Raman microspectroscopy, it was demonstrated that phagocytes contained 70/30 PEO/PBT fragments in their cytoplasm, as intracellular fragments were chemically composed of PEO and PBT. Systemic effects of the fragmentation were not observed in axial lymph nodes. It can be concluded from the data obtained in this model that a PEO/PBT copolymer series was well toierated. This study showed that PEO content in PEO/PBT copolymers is directly related to degradation and calcification of these materials and that the extent of these parameters may vary under different experimental conditions. The application of confocal Raman microspectroscopy enables analysis of the chemical composition of intracellular fragments and may therefore be a valuable instrument in the prediction of long-term implant performances.     

利用字典学习方法的声速剖面反演研究

针对经验正交函数（Empirical Orthogonal Function,EOF）建模反演得到的声速剖面（Sound Speed Profile,SSP）估计值分辨率比较低的问题,文章采用字典学习方法中的K-奇异值分解（K-Singular Value Decomposition,K-SVD）算法生成声速剖面的非正交原子,研究了该方法生成的学习字典（Learning Dictionary,LD）对声速剖面的重建性能。首先,采用K-SVD算法从获得的数据中训练SSP字典,然后利用正交匹配追踪（Orthogonal Matching Pursuit,OMP）的稀疏方法给出训练信号的稀疏向量,最后通过得到的最优学习字典和稀疏向量反演得到SSP的估计值。结果表明,K-SVD算法比EOF算法使用更少的基函数即可很好地描述SSP的变化,获得更高的反演精度。     

Toughened polybutyleneterephthalate compounds

The notch sensitivity of polybutyleneterephthalate (PBT) had been improved in a synergistic way, by 30–40 times, by addition of special toughening agents in limited amounts (20–30%). This large toughening effect was studied by high speed photography. Ultimate elongation strain and strain rate at the notch root were measured directly. It was found that the high impact behaviour of toughened PBT is provided by the large amount of plastic strain around the fracture surface. The plastic strain was not observed in the PBT homopolymer during impact fracture, due to its brittle behaviour; on the contrary, it was observed in low speed bending of notched bars. It was concluded that the toughening mechanism of mixed additives is to allow the plastic strain of a PBT matrix at very high strain rates.Now Himont Italia.     

Effect of Mechanical Activation on the Packed-Bed, High-Temperature Behavior of Hematite and Graphite Mixture in Air

The present study reports the effect of mechanical activation on the reaction behavior of the Fe₂O₃/C powder mixture at high temperature under air atmosphere. Hematite and graphite were ground up to 150 hours using a ball mill with an alumina vial. The mixture was heated isothermally in the temperature range of 1173-1373°K using an electric furnace. The degree of reaction was determined by weight-loss measurement using a high accurate balance. It was found that low-energy mechanical milling at room temperature increases (the degree and) the rate of reaction at constant temperature. However, this effect was more significant at temperatures above 1273°K. At temperatures below 1273°K, the main reaction is oxidation of graphite and the total reaction process is controlled by diffusion of gases, whereas above 1273°K both chemical reaction (gasification reaction) and diffusion were controlling mechanisms. However, increasing milling time would shift the controlling mechanism from diffusion toward pure chemical reaction above 1273°K. It was observed that the mechanical milling might cause the mechanism to be changed at lower temperatures. This could be attributed to the increase of the rate of reaction due to mechanical milling. It was also observed that milling of powder mixture would decrease the difference in the average reaction rates at various degrees of reaction.