一种顶空气相色谱测定乳液聚合过程单体转化率的新方法

介绍了一种通过顶空气相色谱技术测定乳液聚合过程中单体转化率的新方法.通过对聚合乳液样品进行称量方式的采样和大比例的稀释,将已稀释的待测溶液移入顶空瓶中,在设定温度下达到气液平衡后进入气相色谱中测定,其消除了采样的波动性和顶空气相色谱测定的误差,并导出了由顶空气相色谱对样品中单体的测定信号直接计算聚合过程转化率的方程式.该方法具有实验操作简单、快速、检测准确等优点,非常适合乳液聚合反应动力学和机理的研究.     

Determination of Monomer Transfer Constants in Emulsion Polymerization

The monomer transfer constant, C_m can be determined from the chain length distribution (CLD) under conditions in which the monomer transfer reaction rate is much larger than the other chain termination processes. Such reaction conditions are feasible in emulsion polymerization where bimolecular termination reactions are relatively less important. We conducted theoretical investigations aimed at finding the necessary reaction conditions to apply the CLD method to emulsion polymerization. The number of polymer chains per polymer particle needs to be large enough in order to keep the effects of unknown chain lengths to a minimum, i.e., the unknown chains formed during the nucleation period and those which stop growing when the polymerization is stopped for sampling. In emulsion polymerization, the polymer concentration at the polymerization locus is higher than the corresponding bulk polymerization as long as monomer droplets exist, and the polymer transfer reaction may possess significant effects under conditions where monomer transfer reactions are important. The Monte Carlo (MC) simulation results have shown that although the CLD profile becomes broader due to the polymer transfer reactions, they do not significantly change the slope, from which C_m is determined. According to the present simulation results, the CLD method is considered applicable even when the polymer transfer reaction cannot be neglected. The MC simulation method can be used to find the experimental conditions where the CLD method is applicable.     

氯丁胶乳乳液接枝甲基丙烯酸甲酯的反应动力学

采用乳液聚合法将甲基丙烯酸甲酯(MMA)接枝到氯丁胶乳上,红外光谱和核磁共振氢谱证实了接枝产物的生成。 研究了反应温度、乳化剂浓度、引发剂浓度和单体浓度对表观聚合速率的影响。 结果表明,当反应温度为50 ℃,引发剂叔丁基过氧化氢 四乙烯五胺（t-BHP/TEPA）用量为氯丁胶乳干重的0.5%,单体/聚合物质量比m(M)∶m(P)=3∶5,乳化剂十二烷基连苯醚二磺酸钠（DSB）用量为单体总质量1%时,单体转化率和接枝效率分别为99.1%和54.9%。 聚合反应动力学关系式为：Rp=Kc(E)0.15c(I)0.30c(MMA)1.41,式中,K为常数,在40~55 ℃范围内,聚合反应的表观活化能Ea＝60.2 kJ/mol。 接枝聚合基本符合自由基反应机理。     

石英晶体微天平技术在苯胺乳液聚合动力学研究中的应用

采用石英晶体微天平(QCM)技术, 探讨了在有无磁场条件下, 用过硫酸铵(APS)作为引发剂时苯胺的乳液聚合动力学行为. 研究结果表明, 苯胺的乳液聚合反应速率对苯胺(An)是一级反应; 对APS和十二烷基苯磺酸(DBSA)均为0.5级反应. 磁场环境中苯胺的聚合速率比在无磁环境中的要快. 在有无磁场条件下, 反应的表观活化能分别为40.4和41.6 kJ/mol. 结果表明, QCM技术可以作为研究An聚合动力学的一种有效方法.     

Molecular Versus Conventional Kinetics of Emulsion Polymerization

Summary: Experimental data are discussed challenging the deterministic kinetics of emulsion polymerization. Examples are given for the overall rate of polymerization, in-situ stabilizer formation, and swelling of latex particles. Improving the deterministic view on emulsion polymerization kinetics requires the consideration of results of molecular modelling and the application of multiscale integration techniques.     

可乳化共聚单体AGES用于无皂乳液聚合的研究

合成了一种新型可共聚单体烯烃基甘油醚磺酸盐(AGES),不仅含有具有反应活性的烯键,而且带有起乳化作用的磺酸离子基团及羟基,可用于MMA/BA无皂乳液聚合体系。对乳胶粒大小、乳液的流体力学行为及共聚物的动态力学性能进行了研究。实验结果表明:通过AGES的引入,可获得直径为0.5μm左右的分布均匀的乳胶粒,乳液含固量高(60%),粘度低,是稳定的塑性非牛顿流体乳液,共聚物为典型的无规共聚。     

半连续乳液聚合动力学模型

介绍半连续乳液聚合动力学模型的研究进展及建模方法，归结出３种形式模型，基础模型，具体模型与通用模型，指出通常从一些假定出发，根据质量平衡，能量平衡反应机理建立模型方程，通过模型参数估计，已有模型参数的利用及模型变量的求取，使用数值方法求解模型。     

关于八甲基环四硅氧烷乳液聚合反应动力学的回归模拟

本文用数值逼近法对八甲基环四硅氧烷乳液聚合反应的实验结果进行模拟,得到一符合实验事实的动力学方程.     

Process Intensification of Emulsion Polymerization in the Continuous Taylor Reactor

Summary: Process intensification is investigated by the emulsion polymerization of styrene in the continuous Taylor reactor. The result is an increase in space time yield up to a factor 200 in comparison to a semi-batch polymerization process. This is obtained by a fast emulsion polymerization with a mean residence time, which is reduced to 60 seconds. The article presented the results of the process and the economical aspects of the Taylor reactor plant.     

有机硅复合乳液聚合的动力学特征和成核机理

研究了聚合方法、搅拌强度、反应温度及原料用量对ＰＨＭＳ／ＢＡ复合乳液聚合反应转化率、反应速率的影响。结果表明：反应前期,一次加料法比半连续滴加法聚合速率快,但反应终了转化率却略低于后者;聚合反应速率随搅拌强度增大略有降低,随反应温度升高而加快,Ｅａ＝１３２．７７ｋＪ／ｍｏｌ;反应的速率和转化率随ＰＨＭＳ用量的增加而降低,随ＮＭＡ用量的增加而升高。乳液粒径随搅拌强度的主粒径追踪结果表明：乳液粒径随搅     

The Kinetics of Emulsion Polymerization: Some Controversial Aspects

Abstract

Advances in the study of emulsion polymerization (EP) have allowed the clarification of some aspects of the mechanism and kinetics involved. However, such advances have provided controversial information in other aspects. In this work, the authors give a personal view of the state‐of‐the‐art of some of the most controversial issues of the EP kinetics: particle formation (nucleation) mechanism, particle size distribution, evolution of the rate of polymerization, and free‐radical capture.     

一步乳液聚合法制备高溶解性导电聚苯胺

报道了一种高溶解性导电聚苯胺(PANI)的制备方法,以聚2-丙烯酰胺-2-甲基丙磺酸(PAMPS)作为掺杂酸和乳化剂,利用其特有的长链、亲水性及强酸性基团效应,通过乳液聚合法一步合成出具有较高溶解性的导电聚苯胺。利用核磁共振光谱仪(NMR)、傅里叶红外光谱仪(FT-IR)和扫描电子显微镜(SEM)等技术手段对产物结构和性能进行了表征分析。结果表明,在m(苯胺)∶m(AMPS)∶m(APS)=1∶2∶1.5;AMPS质量分数为20%;APS质量分数为30%;反应时间为5 h;反应温度为5℃的条件下,聚苯胺的产率高达86%,在有机溶剂二甲基甲酰胺(DMF)中的溶解度可达0.3814 g/g,在水中的溶解度可达0.2123 g/g,电导率达5.9 S/cm。     

A Study of L-Lactide Ring-Opening Polymerization Kinetics

Summary: The paper presents an experimental study of L-lactide polymerization in molten state using as initiator the Stannous Octoate. The experiments were performed in a Haake mixer. The operating temperatures were between 170 and 195°C, the reaction time up to 60 min and monomer to initiator initial molecular ratio between 10² and 5 · 10³. The conversion was determined by using ¹H NMR and the molecular weights distributions by SEC. A preliminary mathematical modeling study was also performed, based on experimental data and a previously published reaction scheme.     

Kinetics of Radical Polymerization of a Monomer Derived from Monoethanolamine Vinyl Ether and 1,4-Benzoquinone: A Polarographic Study

Radical polymerization of a disubstituted monomer derived from monoethanolamine vinyl ether and 1,4-benzoquinone was studied by classical polarography. The optimal conditions for the synthesis of the redox polymer were found. The polymerization rate constants, preexponential term in the Arrhenius equation, and activation energy were calculated.     

TiCl4共引发乙烯基单体正离子聚合反应动力学及其机理

TiCl4,共引发异丁烯（1B）或苯乙烯（St）进行正离子聚合，聚合反应速率与共引发剂TICl4之间可呈一级和二级动力学关系，这与TiCl4浓度（[TiCl4]）、单体浓度、亲核试剂的亲核性等多方面因素有关。单分子TiCl4与休眠分子链末端进行离子化反应并产生活性中心碳正离子和反离子TiCl5^-，TiCl5^-与另一个TiCl4分子进一步反应则形成双分子反离子Ti2Cl9^-，导致TiCl4表现为二级动力学关系的机理。     

乳液聚合—萃取法制备掺杂态聚苯胺溶液

提出了一种“乳液聚合－萃取”法制备掺杂态聚苯胺溶液的方法。该方法不仅简化了制备步骤，而且减少了有机溶剂的用量从而有利于环境保护。ＳＥＭ，ＵＶ－Ｖｉｓ，ＦＴＩＲ和ＸＰＳ测量表明用该方法所得到的聚苯胺薄膜具有典型的掺杂态聚苯胺的结构特征，证实这种方法的有效性。     

脉冲激光引发自由基聚合的动力学研究

处理了无链转移时脉冲激光引发自由基聚合中的动力学问题:推导出聚合产物数均和重均分子量的严格数学表达式,给出了链自由基、死聚物及总的聚合产物的归一化的分子量分布函数,计算结果表明:随着单体转化率的上升,各种分子参数,例如数均和重均分子量,以及多分散指数的数值周期性地振荡,且振幅逐渐下降,分子量分布曲线则包含一些特征峰,且随着每次脉冲激光产生的初级自由基浓度的降低,分布曲线峰的数目增加,另外,与歧化终止相比,偶合终止使产物的分子量分布略为变窄.     

Study of Soap-free Waterborne Polyurethane-acrylic Emulsion by Polymerization in situ

以二羟甲基丙酸（DMPA）、甲基丙烯酸甲酯（MMA）、异佛尔酮-二异氰酸酯（IPDI）、聚乙二醇（PEG1000）、丙烯酸丁酯（BA）、丙烯酸羟乙酯（HEA）等为基本原料,三乙胺（TEA）作为中和剂,采用原位乳液聚合法合成了水性聚氨酯一丙烯酸酯复合乳液（PUA）。较详细地研究了DMPA的加入量、NCO／OH的比值、固含量、引发剂的种类及加入量、乳化剂种类及加入量等对PUA复合乳液性能以及外观的影响。通过傅立叶变换红外光谱、激光粒度分析仪、凝胶渗透色谱等对合成的PUA复合乳液进行了分析和表征。