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71.
Amphiphilic block copolymers have been investigated for their utilization in emulsion polymerization of butyl methacrylate. Special attention has been paid to the adsorption mechanism of the block copolymers from systematic measurements of equilibrium adsorption isotherms. A series of well-defined water-soluble amphiphilic block copolymers, composed of poly(butyl methacrylate) and poly(sodium methacrylate) blocks, were synthesized by anionic polymerization of butyl methacrylate and tert-butyl methacrylate followed by the thermal deprotection of the tert-butyl ester groups and final hydrolysis. The number density of emulsion polymer particles NP varied as [copolymer]α, α lying between 0.44 and 0.73 according to the hydrophilic content of the copolymers. In contrast with SDS taken as a reference emulsifier, the adsorption of the copolymers was very strong and this provided quite an efficient stabilization of the polymer particles during emulsion polymerization, even at low concentrations (<10−4 mol L−1) and low coverages (<10% of the interfacial area). 相似文献
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对用国内技术建设的万吨级聚合装置生产的5种牌号产品:线型SBS1301,SBS1401和星形SBS4303,SBS4402及充油33%的星形SBS44522进行了性能剖析。结果表明,国产SBS的物理性质、热氧稳定、玻璃化转变温度、微观结构和相态结构与国外同类产品相当,M_n可以达到预期要求,说明该开发技术是成功的。 相似文献
76.
通过对国产SEBS(氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物)流变性能进行测试.分析不同结构、不同嵌段的S/B质量比值、不同相对分子质量、不同加工温度对SEBS产品流变性能的影响.促进用户对国产SEBS性能的了解。 相似文献
77.
Gerhard Maier Vendula Knopfova Brigitte Voit Pham Huu Ly Bui Tien Dung Do Bich Thanh 《大分子材料与工程》2004,289(10):927-932
Summary: Segmented block copolymers, consisting of non‐polar soft segments from hydroxyl‐terminated liquid natural rubber (HTNR) and polar hard segments from α,ω‐diisocyanato telechelics obtained by “criss‐cross”‐cycloaddition, have been synthesized. The block copolymer formation took place under relatively mild reaction conditions at 80 °C in dichloroethane in the presence of dibutyltin dilaurate as a catalyst. The resulting block copolymers were characterized by spectroscopic techniques (1H NMR, FTIR, UV‐vis spectroscopy) as well as GPC for molar mass determination. The block copolymers were compression molded in a hot stage press, and the resulting samples were characterized by DSC and stress‐strain measurement. The solubility and phase morphology of the materials have also been studied.
78.
Han Mo Jeong Shang Hoon Lee Kwang Jae Cho Young Tae Jeong Kap Ku Kang Jae Kwon Oh 《应用聚合物科学杂志》2002,84(9):1709-1715
The block copolymer of poly(1‐hexadecene) (PHD) and polypropylene (PP) was effectively synthesized by the sequential polymerization of propylene and 1‐hexadecene by using highly isospecific TiCl3/Cp2Ti(CH3)2 (Cp = cyclopentadienyl). The block copolymers had two separate melting temperatures of constituent blocks. The modulus of PHD–PP block copolymer was enhanced as the content of sequentially polymerized PP block was increased. The elongation at break showed positive deviation at the intermediate compositions from the simple additive values of constituent homopolymers. Shape memory effect which utilizes the crystalline PHD block as a reversible phase and the crystalline PP block as a fixed structure was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1709–1715, 2002; DOI 10.1002/app.10551 相似文献
79.
The present work investigates the relationships between the microstructural state and fracture properties in commercial polypropylene‐based materials. In this case an isopolypropylene homopolymer and three ethylene propylene block copolymers (EPBC) with different ethylene content (EC) have been studied. A variety of morphologies were obtained by a combination of several processing methods (injection molding, injection molding‐annealing, and compression molding) and thickness. Fracture behavior of deeply double‐edged notched specimens was evaluated by scanning electron microscopy (SEM) and by the essential work of fracture (EWF) method, analyzing the influence of processing, thickness (t), EC, and orientation respect to melt flow direction (MD and TD). The testing direction and EC are the most relevant variables that affect the ability of the crack tip to deform plastically during the crack propagation, determining the final fracture behavior. The fracture parameters obtained with the EWF method, specific EWF, we, and plastic item, βwp, have proved to be very sensitive to the processing induced morphology, finding interesting relationships between such morphologies (characterized by crystallinity index, orientation level, and skin/core ratio) and the fracture parameters of the plaques. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2714–2724, 2006 相似文献
80.
徐国天 《网络安全技术与应用》2014,(11):32-33
本文设计了一款不依赖日志文件的oracle数据库综合检验、恢复工具。该工具可从oracle数据文件(*.dbf)中检测出所有数据表(包括"被删除"数据表)的详细信息,例如表名称、字段名、字段类型、字段长度、字段序号和表数据实际保存的数据块号。该工具可在日志文件被清除的情况下直接从数据文件中恢复出被删除的记录,准确率达到100%。该工具可从数据文件中恢复出某些"被删除"的数据表。 相似文献