共查询到20条相似文献,搜索用时 171 毫秒
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介绍了烷基锂负离子聚合工艺存在的主要弊端,同时指出适当降低高反应速率的途径是调控活性种的反应性。阐述了Lew is酸改性烷基锂负离子聚合的研究进展,认为酸根型络合物反应性和选择性的设定是调控活性负离子聚合的关键,是研发新型负离子引发体系的重要内容。 相似文献
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综合分析了近年来有关(甲基)丙烯酸烷基酯负离子聚合所得的成就,包括该类单体对负离子聚合,聚合难点和解决办法。介绍了聚合和单官能团引发剂体系。 相似文献
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简要介绍了德国BASF公司通过阻滞负离子聚合开发出制造高抗冲聚苯乙烯的新工艺,指出了由Lewis酸添加剂改性碱金属引发负离子聚合的发展趋势. 相似文献
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以环己烷为溶剂、三异丁基铝为阻滞剂、丁基锂为引发剂,研究了三异丁基铝与丁基锂摩尔比[n(Al)/n(Li)]和聚合温度对苯乙烯阻滞负离子聚合反应速率和动力学的影响规律,对相应的假一级表观增长速率常数进行了求解.结果表明,采用三异丁基铝/丁基锂体系引发苯乙烯阻滞负离子聚合,在苯乙烯转化率较低(小于60%)时,苯乙烯聚合速... 相似文献
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介绍了三异丁基铝/聚苯乙烯基锂活性种引发苯乙烯阻滞负离子聚合的一些特性,评述了不同铝衍生物如烷基铝、氢化二异丁基铝和二乙基烷氧基铝对苯乙烯在高温下烃介质中的负离子聚合的影响,指出烷基铝添加剂的结构和[Al]/[Li](摩尔比)对酸根型络合物的形成、聚合的阻滞效应以及反应性有重要作用,这类引发体系为苯乙烯高温阻滞负离子聚合提供了很宽的操作范围。 相似文献
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采用负离子溶液聚合法,以仲丁基锂为引发剂、环己烷为溶剂、四氢呋喃为结构调节剂,以及1,1-双(4-二甲基氨基苯基)乙烯为官能化共聚单体与丁二烯和苯乙烯进行活性负离子共聚合,制备了二甲氨基链中多官能化丁二烯-苯乙烯共聚物,考察了聚合温度和结构调节剂用量对聚合动力学和聚合物微观结构的影响。结果表明,共聚物链中二甲氨基官能团数量可通过调整聚合温度和结构调节剂用量进行准确控制,随聚合温度升高和四氢呋喃用量的增加,单体的总反应速率和转化率都逐渐增大;聚合物中1,2-结构的含量随结构调节剂用量的增加而逐渐增大,随聚合温度升高而逐渐减小。求得聚合温度为50 ℃时丁二烯和苯乙烯单体的平均竞聚率为69.67。 相似文献
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Summary In this study, stable concentrated emulsions of methyl methacrylate and butyl acrylate (MMA-BA) were first prepared using
sodium dodecyl sulfate/cetyl alcohol (SDS/CA) as composite surfactants and polyvinyl alcohol (PVA) as liquid film reinforcer.
A novel polymerization method, thin layer copolymerization of the concentrated emulsion was subsequently carried out with
benzoyl peroxide/N, N’-dimethyl phenylamine (BPO/DMA) as redox initiators at low temperature. The effects of the thickness
and area of the thin layer, the outside temperature, as well as environment of the polymerization on the amount of volatilization
of water and monomer in the system were investigated. It has been found that the liquid film reinforcers and the polymerization
environment were responsible for the polymerization stability. In addition, the conversion-time relationships of the thin
layer polymerization and the tube polymerization, as well as the effect of polymerization environment on the polymerization
rate were also investigated. The size and distribution of particle diameter and morphology of latex particles were determined
with transmission electron microscope (TEM). 相似文献
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以D-山梨醇为引发剂,二甲亚砜为溶剂,氢氧化钾为催化剂,环氧乙烷为单体,阴离子开环聚合合成了多官能度聚乙二醇。详细考察了催化剂、引发剂、溶剂、聚合温度等因素对聚合产物的性能影响。初步确定了聚合条件,聚合温度100~110℃,聚合时间6h。通过官能度的理论计算和测试证明合成的聚合物为多官能度聚乙二醇。 相似文献
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Stable concentrated emulsions of polymerizable polysiloxane‐containing polyurethane (PUASi)/Styrene (St)/Methyl methacrylate (MMA) were prepared using sodium dodecyl sulphate (SDS)/nonyl polyoxyethylene ether (OS15)/polyvinyl alcohol (PVA) as composite surfactant and azobisisobutyronitrile (AIBN) as initiator. A novel polymerization method, thin layer polymerization was used to carry out the concentrated emulsion copolymerization at 55°C. The effects of TDI/PPG molar ratio, surfactant concentration, different kinds of surfactants, and temperature on polymerization stability were studied. The effects of the thickness of the thin layer, the outside temperature of the reactor, as well as polymerization environment on the volatilization rate of water, and monomer in the system were investigated. The conversion‐time relationships of the thin layer polymerization and the tube polymerization, as well as the effect of polymerization environment on the polymerization rate were also investigated. The morphology of latex particles was determined with transmission electron microscope (TEM). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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在八甲基环四硅氧烷(D4)为单体,十二烷基苯磺酸 (DBSA)为乳化剂和催化剂,正戊醇(C5H11OH)为助乳化剂的单体微乳液体系中,进行D4的微乳液聚合.研究了聚合温度、乳化体系组成、交联剂乙烯基三甲氧基硅烷(VTMS)对D4微乳液聚合动力学的影响.结果表明:微乳液聚合没有常规乳液聚合的恒速反应期,在较高温度下,反应迅速进入快速反应阶段,达到一定转化率后又快速下降并趋于平衡转化率.高温有利于加快聚合速率.适当增大乳化剂DBSA与助乳化剂的比例,单体微滴的尺寸减小,聚合速率增大,产物粒径减小.交联剂VTMS的引入,不仅使线性聚硅氧烷形成交联的弹性体网络,而且改变了端羟基硅氧烷的缩合平衡反应速率,抑制了逆反应,加快了聚合速率. 相似文献