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The interaction of acid comonomers, crotonic acid, maleic monoesters, maleic acid with the surfactant, the sodium salt of sulfosuccinic acid semiester with nonyl phenol etoxylated with 25 moles ethylene oxide (NPEO25SS) depends on the hydrophilicity of comonomers. The rate of initiator splitting reaction (potassium persulfate - KPS) in presence of NPEO25SS and of comonomers decreases with the increasing of acid comonomer concentration. This rule is valid in copolymerization of acid comonomers with vinyl acetate (VAc) below a small comonomer concentration, then the rate increases. The presence of some more hydrophobic comonomers maleic diesters, lowers the decomposition rate of KPS. These results are the effect of the stronger interaction of NPEO25SS with more hydrophobic polymer particles. In their presence the concentration of free NPEO25SS is lower and it can participate in the KPS - surfactant reaction and rise its rate to a lesser extent. Owing to some secondary acid comonomer - KPS reactions the productivity of initiator splitting decreases with acid comonomer concentration The glass transition temperatures of the thin films obtained in presence of acid comonomers, may increase or decrease, depending on the volume of the substituents of these comonomers. 相似文献
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通过正离子交换将引发剂AIBA负载在蒙脱土上制得负载型引发剂V50-MMT.进而采用原位乳液聚合方法引发苯乙烯聚合制备PS/MMT纳米复合材料.采用XRD、TGA、DSC、TEM和抽提等方法对负载型引发剂和纳米复合材料进行了表征.结果表明,负载过程中引发剂AIBA进入了MMT的片层之间;聚合过程中介于片层间的引发剂因发生分解一方面产生自由基引发St聚合,另一方面MMT发生了剥离分散;由此法制备的PS/MMT纳米复合材料,MMT片层无规、均匀地分散于PS基体中,片层厚度在几个纳米至十几个纳米之间,长度为几十至几百个纳米不等;大量的PS链段以化学键接枝在MMT的片层上,接枝在MMT片层上的PS的分子量及其分布与游离的PS不同. 相似文献
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Dan Donescu Liana Fusulan Sever Serban Filip Chiraleu Cristian Petcu 《Journal of Dispersion Science and Technology》2013,34(7):701-715
Abstract The homogeneity ranges of the systems consisting of the monomer (vinyl acetate or vinyl acetate + di-2-ethyl hexil maleate), cosurfactant (ethanol, n-propanol, n-butanol), surfactant (nonylphenol ethoxylate with 25 moles of ethylene oxide) and water were studied. Addition of the more hydrophobic comonomer requires utilization of a more hydrophobic cosurfactant. The increase of surfactant concentration entails the widening of the homogeneity range. The effect of the cosurfactants mentioned is accounted for by the modification of the cluster structure of water. Therefore the refractive indexes and the signals of protons in NMR spectra vary non-linearly with the composition of homogeneous systems. DSC analysis of the systems obtained has come out with two crystallization temperatures of water undercooled to ?60°C in systems of concentrations close to those of organic and aqueous phases. The results plead for the existence of a structure which differs from that of the ideal solutions of the systems studied. 相似文献
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在阳离子乳化剂的存在下八甲基环四硅氧烷的乳液聚合 总被引:1,自引:0,他引:1
研究了八甲基环四硅氧烷(D_4)在十二烷基二甲基苄基卤化铵及碱存在下乳液聚合的反应机理。聚合分二步进行:D_4先开环生成具有端羟基的聚二甲基硅氧烷,然后再缩合。反应终点有二个平衡反应;不同分子量的羟基封头的聚二甲基硅氧烷的平衡,以及羟基封头的线型聚硅氧烷和环硅氧烷的平衡。平衡时羟基封头的聚硅氧烷的量为87%并提出了主要反应位置是在胶束表面并逐渐转移到随后形成的聚合物颗粒表面,单体液滴是次要反应区。 相似文献
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醋酸乙烯酯-丙烯酸丁酯乳液聚合成核机理 总被引:5,自引:2,他引:5
本工作研究了醋酸乙烯酯(VA)和丙烯酸丁酯(BA)乳液共聚合.通过对不同共聚单体配比下共聚合时胶乳粒径及胶粒数密度随转化率变化的分析,对VA/BA乳液共聚合成核及粒增长机理进行了探讨,指出水相成核是高VA含量时胶粒数密度较大的主要原因并解释了胶粒数密度及胶乳粒径与单体转化率的关系,同时也讨论了该共聚体系一步法聚合时反应机理与胶粒形态的关系. 相似文献
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The kinetics of the decomposition of cyclohexyl hydroperoxide(CHHP) in benzene catalyzed by vanadyl dibenzoylmethane[V0(DBM).,] has been studied.It was found that the products of decomposition of CHHP were cyclohexanol and cyclohexanone,which are produced in about equimolar amount,and the product cyclohexanol obviously inhibited the decomposition of CHHP.The kinetics data can be satisfactorily described by the following equation (with [CHHP]0>>[VO(DBM)2]0)R0=kK[CHHP]0[VO(DBM)2]0/(1+k[CHHP]0)This is the kinetic evidence for the formation of a catalyst-hydro-peroxide intermediate.In the equation K is the stability constant of the catalyst-hydroperoxide intermediate complex;k is the rate constant for the decomposition of the complex.The rate constant K at 500℃ may be expressed as follows:k=1.9×108exp(-53.7×103/RT)S-1 with the activation energy Ea=53.7kJ mol-1 相似文献
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J.W. Vanderhoff F.V. DiStefano M.S. El-Aasser R. O'Leary O.M. Shaffer D.L. Visioli 《Journal of Dispersion Science and Technology》2013,34(3-4):323-363
Inverse emulsion polymerization confers the benefits of emulsion polymerization kinetics — rapid polymerization rates combined with high polymer molecular weights — on water-soluble polymers, particularly polyacrylamide and its copolymers and derivatives, and allows easy dissolution of the polymer in water by inversion of the latex. The mechanism and kinetics of the inverse emulsion polymerization of acrylamide in o-xylene containing Tetronic 1102 emulslfier and benzoyl peroxide initiator are described, particularly the formation of 10-200nm multiple emulsion droplets resulting from the particulate emulsifier, and their effect on the polymerization process 相似文献
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This paper provides a summarized review on the kinetics of vinyl chloride homopolymerization inthe absence and presence of chain transfer agents, of VC/DAP(diallyl phthalate) copolymerization with chainextension and/or slightly crosslinking functions, and of vinylidene chloride/VC random copolymerization.Models of rate, degree of polymerization or molecular weight, copolymer composition, gel fraction andcrosslinking density were proposed and interpreted mechanistically. 相似文献
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在四官能团引发剂存在下的自缩合乙烯基聚合反应制备丙烯酸酯类超支化共聚物 总被引:5,自引:0,他引:5
超支化聚合物具有特殊的结构和性能 ,可通过一步法聚合直接制得 ,具有大规模工业应用前景 .近年来 ,超支化聚合物的研究已成为高分子科学的热门课题之一[1~ 3 ] .超支化聚合物的一个主要缺点是它的分子量分布比较宽 .M櫣ller[4] 等通过理论计算指出 ,在聚合体系中加入f个功能基团的分子Bf[对自缩合乙烯基聚合反应 (SCVP) ,Bf为f个引发基的引发剂 ;对ABx 型单体的缩聚反应 ,为有f个B官能团的分子 ],可以降低超支化聚合物的分子量分布 ,这一结果已被实验证实[5~ 7] .我们用MonteCarlo方法模拟了在多官能团引… 相似文献
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