成核剂对不同特性粘数PET结晶性能的影响

研究了新型复合成核剂水滑石(HT)／离聚物(Surlyn8920)／聚乙二醇(PEG)对不同特性粘数聚对苯二甲酸乙二醇酯(PET)非等温结晶性能的影响。通过差示扫描量热仪测试了PET的结晶峰温度T_(mc)和熔融峰温度(T_m)。结果表明,复合成核剂各组分及PET的质量比为0.5:3.0:3.0:100.0时,各种PET的过冷度(T_m-T_(mc))均显著减少．半结晶时间(1gt_(1／2))也明显降低。而且,复合成核剂对不同特性粘数PET结晶性能的改善是一致的。     

Crystal lattice deformation and the mesophase in poly(ethylene terephthalate) uniaxially drawn by solid-state coextrusion

The development of crystalline and mesophase structure on drawing of poly(ethylene terephthalate) (PET) has been studied. The uniaxial drawing has been done by solid-state coextrusion from 50 to 90°C. The unit-cell parameters of stress-induced crystallites in extrudates have been determined as a function of extrusion draw ratio (EDR) up to 4.4 and at an extrusion temperature (ET) above T_g, at 70 and 90°C. The higher the EDR, the longer the c-axis chain direction, the shorter the a and b axes and the smaller the unit-cell volume. In comparison with the conventional lattice parameters obtained by Bunn and Fisher, the highest elongation of the c axis is near 10%. These features imply that the lattice of stress-induced crystallites is far from the closest packing. Coextrudates made below the T_g of PET differ markedly from those made above T_g. Wide-angle X-ray diffraction (WAXD) patterns of PET extruded at 50°C (below T_g) even at high draw ratio exhibit small and/or imperfect crystallites. They appear much as a mesophase. The distance between macromolecular chains ranges from 3.2 to 5.4 Å. The shortest value in the mesophase approaches the interplanar crystal distance of 3.4 Å for the (100) crystal face, on which the benzene rings lie. The crystalline peak separation of the PET, WAXD curve has been evaluated to obtain absolute crystallinities and the content of mesophase and amorphous phase.     

基于Pro/TOOLKIT异步模式特征识别方法

对Pro／Engineer（Pro／E）二次开发工具Pro／TOOLKIT（PTC公司为Pro／E软件提供的二次开发工具包）的异步模式进行了研究，充分利用参数化技术，开发了实体模型的特征识别系统。系统可以控制Pro／E的自动启动及关闭，使其在后台运行。通过模型的调用实现实体特征的快速识别提取，为模具估价系统的智能化设计做好了准备。     

压挤成形--固化法制备0-3型压电复合材料的性能研究

详细地叙述了室温压挤成形———固化工艺制备 0 -3型压电复合材料工艺 ,使用XRD、SEM和HP42 94测试并分析了样品的结构和性能 ,并与压电陶瓷性能参数进行了对比 ;同时用这种工艺制备可以获得介电损耗小、机电耦合系数为 2 5 .11%、压电应变常数为 3 2PC N和机电品质因数可达到 3 0 2的 0— 3型压电复合材料。     

Bending behavior of an electrically activated complex forming hydrogel

Summary The complex forming poly[(ethylene glycol-co-proplene glycol)-g-acrylamide]: polyacrylic acid interpenetrating polymer network hydrogel is able to bend under electric field stimuli. pH, ionic strength gradients and voltage can influence it's bending degree. So we may improve the sample' responsive speed through manipulating those factor in the further study in order to put it into the biomedical application.     

Neutral Pd(II) and Ni(II) Acetylide Catalysts for the Polymerization of Methyl Methacrylate

Homogenous polymerization of methyl methacrylate using Pd(II)- and Ni(II)-based acetylide complexes as initiators has been investigated. M(PR'₃)₂(CCR)₂ (M=Pd, Ni; R'=PPh₃, Pn-Bu₃; R=Ph, CH₂OH, CH₂OOCCH₃, CH₂OOCPh, CH₂OOCPhOH-o) were found to be a novel type of effective initiators for the polymerization of methyl methacrylate. Among them, Pd(C CPh)₂(PPh₃)₂ (PPP) shows the highest activity in the MMA polymerization and the PMMA obtained is a syndiotactic polymer with high number-average molecular weight (M _n) of 14.1 × 10⁴. Some features and kinetic behavior of MMA polymerization initiated by PPP were studied in detail. The polymerization reaction is first-order with respect to both [PPP] and [MMA]. Radical polymerization mechanism is proposed.     

沥青带水磺化工艺的研究

通过沥青磺化过程的主反应和副反应，进一步讨论了磺化工艺的原理，磺化试剂的选择，溶剂的组成，带水速度，溶剂的回收方式等各种因素对产品质量的影响。     

铝锆炭滑板在浇铸钙处理钢时的化学侵蚀

利用扫描电镜对抗钙处理钢液侵蚀试验后的铝锆炭残样进行了显微结构观察 ,并分析了铝锆炭滑板在钙处理钢液中的化学侵蚀机理。结果表明 :高温下 ,钙处理钢液中的Ca及CaO会与滑板中的Al2 O3 、SiO2 发生反应 ,生成低熔点的 12CaO·7SiO2 (1392℃ )和 2CaO·SiO2 ·Al2 O3 (15 39℃ )等物质 ,这些低熔物被钢水冲刷掉 ,使得滑板表层的Al2O3 和SiO2 含量迅速降低 ,从而导致了滑板的损毁。     

Preparation and characterization of sulfonated polyetherimide/polyetherimide blend membranes

Polyetherimide (PEI) was sulfonated by chlorosulfonic acid (CSA) in 1,2‐dichloroethane for the first time. With the increase of the CSA/PEI repeat unit ratio and/or reaction time, the ion‐exchange capacity (IEC) of the sulfonated polyetherimide (SPEI) increased accordingly. Water‐uptake testing and contact‐angle measurement showed that the hydrophilicity of the SPEI increases with the increase of the IEC. Membranes were fabricated from SPEI/PEI blends with different ratios. The morphologies of the blend membranes were examined by scanning electron microscopy, which showed that the membrane pore size is larger when SPEI with higher IEC was used. With the increase of SPEI ratio in the blend membranes, the membrane pore size also increased. The contact‐angle data of the membranes showed that the hydrophilicity of the blend membrane was elevated because of the sulfonate group on the SPEI molecular backbone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1709–1715, 2004     

Free radical grafting of glycidyl methacrylate onto polypropylene in a co-rotating twin screw extruder

Free radical grafting of glycidyl methacrylate (GMA) onto molten polypropylene (PP) was studied in a co-rotating twin screw extruder. Grafting yields of GMA obtained under various experimental conditions along the screw length allowed for a good appreciation of the effects of chemical parameters (the presence of styrene and the concentrations of peroxide and monomers) and those of processing parameters (feed rate, screw speed, and specific throughput). Similar to the results obtained in a batch mixer,¹ free radical grafting of GMA carried out in the extruder in the presence or absence of styrene proceeded rapidly, as it was virtually completed half-way down stream of the extruder. Additionally, the presence of styrene as a second monomer increased the GMA grafting yield reatly with reduced PP chain degradation. The ultimate GMA grafting yield increased with increasing concentration of peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene. This similarity between the batch mixer and the extruder is related to the fact that in both cases it is the concentration of the peroxide and its half lifetime that determine the grafting rate and the ultimate grafting yield. On the othe hand, the GMA grafting yield decreased with increasing screw speed or feed rate. For a particular specific throughput (the ratio of throughput to screw speed), an increase in throughput with a concomitant increase in screw speed brought about a decrease in GMA grafting yield. It was concluded that the GMA grafting yield is affected primarily by the residence time in the zone in which free radicals are not depleted. The effects of screw speed, feed rate, and specific throughput manifest mainly through this local residence time distribution. Specific energy is not a good measure of the performance of the extruder with respect to the free radical rafting of GMA onto PP. © 1995 John Wiley & Sons, Inc.