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Fundamentals of emulsion of polymerization studied by reaction calorimetry.

机译：通过反应量热法研究聚合乳液的基本原理。

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Various fundamental aspects of the kinetics of emulsion polymerization were studied using reaction calorimetry to measure the actual kinetic profile. The major part of this investigation was carried out with styrene as the model monomer. The bench mark for comparison of results was a well characterized reaction reported in the literature for the system Styrene/sodium lauryl sulfate/potassium persulfate from which Stage II was defined as a reaction interval with increasing heat of reaction and increasing number of particles after the micelles disappearance. The three main objectives for the project were to gain understanding of the variables affecting the rate of polymerization during Stage II, to investigate the variables controlling the disappearance of monomer droplets and to evaluate the universality of Stage II.;To accomplish the goals, several series of reactions were carried out to evaluate the effect of the surfactant type and concentration, the effect of ionic strength and free radical charge, the effect of rate of decomposition of initiator, the effect of electrostatic interaction between the surfactant and the initiator, and the effect of monomer properties such as water solubility and propagation rate coefficient. The calorimetric profiles obtained in reactions with sodium lauryl sulfate, Aerosol MA-80 and Abex EP-110 were in agreement with results from Varela de la Rosa regarding the duration of Stage II and the magnitude of the increase in Qr. A significant increase in the number of particle during Stage II was observed only in some of the reactions; although the magnitude and duration was smaller than in previous works.;Our results confirmed the observation of Stage II nucleation in the S/SLS/KPS system at surfactant concentrations above 8 times the cmc, whereas no increase in Np was observed in this system at surfactant concentrations between 1.1 and 5 times the cmc. In the case of the system S/Aerosol MA/KPS we found that Stage II nucleation is present even at total surfactant concentrations below 1.5 times the cmc. The difference between the free energy of adsorption and free energy of micellization together with the dynamics of micelle formation and surfactant adsorption were discussed to provide a proposed explanation of these observations.;Stage II nucleation was also observed in reactions carried out with other surfactants or initiators although some reactions did not show any Stage II nucleation. For systems other than S/SLS/KPS the increase in N p was not observed usually for reactions with final particle size larger than 80 nm although it was commonly observed in reactions with final particle size below 60 nm. In some cases the magnitude and conversion range for this increment was reduced by updating the calibration used in the particle size analysis. TEM analysis and CHDF characterization confirmed that the Np became fixed at the beginning of Stage II for other systems studied including Styrene and Methacrylic monomers polymerized with anionic and cationic initiators or surfactants.;The results obtained in a series of reactions carried out with styrene at 20% solids and 50°C with increasing ionic strength using three different initiator systems, namely, potassium persulfate, VA-044 and hydrogen peroxide/ascorbic acid, indicated that regardless of the reaction components the number of particles became fixed when the average particle size of the PSD in the reaction reached a value between 36 and 41 nm. This finding could be indication that Stage II nucleation is controlled by the collision model for capture of precursor particles.;Another significant finding of this investigation was that the rate of polymerization during Stage II can vary in many different ways, and not only with an increasing profile. (Abstract shortened by UMI.).
机译：使用反应量热法研究了乳液聚合动力学的各个基本方面，以测量实际的动力学曲线。该研究的主要部分是使用苯乙烯作为模型单体进行的。比较结果的基准是文献中报道的苯乙烯/十二烷基硫酸钠/过硫酸钾系统的特征明确的反应，其中阶段II定义为反应间隔，随着反应热的增加和胶束后颗粒数量的增加消失。该项目的三个主要目标是加深对阶段II中影响聚合速率的变量的了解，研究控制单体液滴消失的变量并评估阶段II的普遍性。进行反应的评估以评估表面活性剂类型和浓度的影响，离子强度和自由基电荷的影响，引发剂分解速率的影响，表面活性剂与引发剂之间的静电相互作用的影响以及该影响。单体特性如水溶性和传播速率系数的关系。与月桂基硫酸钠，Aerosol MA-80和Abex EP-110反应获得的量热曲线与Varela de la Rosa关于II期持续时间和Qr增加幅度的结果一致。仅在某些反应中，观察到第二阶段的颗粒数量显着增加。尽管其幅度和持续时间都小于以前的工作。;我们的结果证实，在表面活性剂浓度高于cmc的8倍时，在S / SLS / KPS系统中观察到了第二阶段成核，而在该系统中，Np却没有增加。表面活性剂浓度为cmc的1.1至5倍。对于系统S / Aerosol MA / KPS，我们发现即使表面活性剂的总浓度低于cmc的1.5倍，也存在II期成核。讨论了吸附的自由能和胶束化的自由能之间的差异，以及胶束形成和表面活性剂吸附的动力学，为这些发现提供了解释性解释。在与其他表面活性剂或引发剂进行的反应中也观察到了II期成核尽管某些反应未显示任何II期成核。对于除S / SLS / KPS以外的系统，通常在最终粒径大于80 nm的反应中未观察到N p的增加，尽管通常在最终粒径小于60 nm的反应中观察到。在某些情况下，可以通过更新粒度分析中使用的校准来减小此增量的幅度和转换范围。 TEM分析和CHDF表征证实，对于其他研究的体系（包括与阴离子和阳离子引发剂或表面活性剂聚合的苯乙烯和甲基丙烯酸单体），Np在第二阶段开始时就固定了;在20°C与苯乙烯进行的一系列反应中获得的结果使用三种不同的引发剂系统（即过硫酸钾，VA-044和过氧化氢/抗坏血酸）在50％的固体和50％的离子强度下随离子强度的增加而表明，无论反应组分如何，当平均粒径为50％时，颗粒数都变得固定反应中的PSD达到36至41 nm之间的值。这一发现可能表明第二阶段的成核是由碰撞模型控制的，以捕获前体颗粒。该研究的另一个重要发现是，第二阶段的聚合速率可以以许多不同的方式变化，并且不仅随着轮廓。 （摘要由UMI缩短。）。

著录项

  • 作者

    Ortiz Alba, Emilio.;

  • 作者单位

    Lehigh University.;

  • 授予单位 Lehigh University.;
  • 学科 Chemistry Polymer.;Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 287 p.
  • 总页数 287
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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