建筑涂料用苯丙乳液的研制

本文采用自由基乳液聚合方法，通过苯乙烯，丙烯酸丁酯和丙烯酸三元共聚反应，合成了建筑涂料用的苯丙乳液。通过大量的实验确定了反应配方及加料方式，并详细讨论了各组分及反应条件对聚合反应和产品性能的影响。     

反应性乳化剂存在下的五元苯丙乳液共聚合

采用反应性乳化剂SE-10N,通过正交实验及单因素实验确定了以苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸和丙烯腈为单体的五元无皂苯丙共聚乳液的组成及聚合工艺。所制得的无皂乳液稳定,其乳胶粒大小均匀,粒径为50~60nm,比同组成的有皂乳液乳胶粒的粒径稍小。乳液涂膜透明、硬度达H级;其硬度、耐水性及钙离子稳定性均较同组成有皂乳液的好。     

苯丙水溶胶的合成与性能研究(II) 水溶胶的转化及其流变性能

用一次投料法、半连续滴加法和单体预乳化法3种聚合工艺，合成了苯丙乳液聚合物，并加氨微细化，转化成水溶胶，研究了水溶胶的氨化反应对乳胶粒子大小及微观形成的影响。并考察了水溶胶的流变性能。     

基于氧化淀粉的新型Pickering苯丙乳液表面施胶剂的合成

以苯乙烯、丙烯酸丁酯为单体,过硫酸铵为引发剂,氧化淀粉作固体粒子乳化剂,采用无皂乳液聚合的方法来制备Pickering苯丙聚合物乳液,考察了不同含量的氧化淀粉对乳液固含量、转化率、卡伯值以及稳定性的影响,并对制备的Pickering苯丙聚合物乳液进行了粒径、红外光谱表征,当氧化淀粉的含量为2%时,制备的Pickering苯丙聚合物乳液转化率为96%,粒径为264.4nm,卡伯值为71.4g/m~2,抗水性和稳定性较好.     

有机硅改性苯丙乳液的研究进展

综述了有机硅改性苯丙乳液的机理、方法和聚合技术研究进展.介绍了物理共混法和化学改性法,重点阐述了化学改性法的最新研究进展,并展望了有机硅改性苯丙乳液的发展趋势.     

改性苯丙乳液的合成及用于浸渍滤纸的研究

油品中的微量水分是降低油品质量,威胁发动机安全寿命的主要因素。为了制备优良的油水分离滤纸,本研究首先采用半连续乳液聚合法合成改性苯丙乳液,研究了乳化剂用量及比例、引发剂用量等对乳液稳定性的影响。结果显示,复合乳化剂用量为0.8-1.0 wt%,引发剂用量为0.8 wt%,交联单体用量为3 wt%,反应温度为80℃时,制备的改性苯丙乳液具有良好的稳定性,乳液粒径分布均匀。在上胶量为20±0.5 wt%时,此乳液浸渍的滤纸耐破度为304 kPa,拉伸强度为4.18 kN.m~(-1),耐水时间为24.0 h。水滴在浸渍滤纸表面上的接触角为110.2°,而煤油的接触角为25.6°。本研究为改性苯丙乳液在发动机滤纸上的应用提供了基础数据。     

有机氟改性苯丙乳液的合成及其性能

苯丙乳液;含氟甲基丙烯酸酯;氟碳表面活性剂;单体转化率;吸水率     

反应性复合乳液的合成、表征及其交联反应

利用种子半连续乳液聚合方法合成了核层或壳层带有环氧基以及壳层带有羧基的3种不同核/壳结构的乳胶粒子,通过物理共混带环氧基和羧基的乳胶粒子,得到了两种反应性复合乳液.利用透射电镜和激光动态光散射对乳胶粒子进行了表征,其粒径分布较窄,粒径分布的多分散系数为0.062,平均粒径约76 nm,乳胶粒子具有明显的核/壳结构.通过胶膜的凝胶率和膨胀率的测定和红外光谱分析对反应性复合乳液中乳胶粒子的扩散及交联反应进行了研究,并探讨了不同核壳结构复合乳液对涂膜机械性能的影响.研究表明,当反应性复合乳液中的环氧基和羧基分别分布在乳胶粒子的核层和壳层时,有利于聚合物分子链的充分扩散和化学交联反应的进行,从而提高涂膜的物理化学性能,当甲基丙烯酸缩水甘油酯(GMA)含量为10 wt%时,涂膜的拉伸强度达20.3 MPa.     

反应性乳化剂在无皂硅溶胶苯丙乳液聚合中的应用

反应性乳化剂;硅溶胶;苯丙乳液;乳液聚合     

有机硅改性丙烯酸酯乳液的合成

乳液聚合;涂料;有机硅改性丙烯酸酯乳液的合成     

Electrosteric stability of styrene/acrylic acid copolymer latices under emulsion polymerization reaction conditions

Acrylic acid (AA) is used in many emulsion polymerization formulations to improve the colloidal stability during and after the production of latex products. Theoretically, the improved stability originates from electrostatic repulsion complemented with steric repulsion. The objective of this work was to study the contribution of AA to the colloidal stability of polystyrene and styrene/AA copolymer latices under simulated reaction conditions. The strength of electrostatic and steric repulsion forces as a function of the electrolyte concentration, pH, and temperature was investigated via coagulation experiments with monomer‐swollen latices in stirred tank reactors. Transmission electron microscopy pictures and dynamic light scattering measurements provided an understanding of the conditions and mechanisms leading to coagulation. The experiments demonstrated that the presence of surface‐bound carboxylic groups only improved the colloidal stability if the carboxylic groups were charged, that is, at a high pH. At a low pH, the copolymer latices were even less stable than the homopolymer latex, and this indicated that the addition of AA did not improve the colloidal stability of a growing polystyrene latex. With respect to emulsion polymerization process operations, insufficient mixing and a highly concentrated electrolyte feed were found to be sources of fouling and enhanced macroscopic coagulation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 726–732, 2005     

Details of the emulsion polymerization of styrene using a reaction calorimeter

An automated reaction calorimeter was used to directly monitor the rate of emulsion polymerization of styrene using different emulsifier (sodium lauryl sulfate) and initiator (potassium persulfate) concentrations. By using this technique in conjunction with off-line measurements of the evolution of the particle size distributions, important details of the process were observed. The classical constant rate period (Interval II) often reported for the batch emulsion polymerization of styrene was not seen in this work. Instead, the experimental results suggest that the end of nucleation and the disappearance of monomer droplets take place at approximately the same conversion (36–40%). From the polymerization rate data, important parameters such as the monomer concentration in the polymer particles and the average number of radicals per particle were calculated. © 1996 John Wiley & Sons, Inc.     

Effect of dose rate on emulsion and microemulsion polymerization of styrene

Emulsion and microemulsion polymerization of styrene were initiated with a gamma ray to study the effect of dose rate on polymerization. In both systems, there is an apparent plateau of polymerization rate in the curve of reaction rate vs. conversion. It was shown that emulsion polymerization conformed to the Smith–Ewart theory very well. Changing the dose rate in interval 2 had no great influence on polymerization rate, but it changed the average lifetime of radicals in polymer particles and affected the molecular weight of polymer produced. For microemulsion polymerization it was assumed that in the plateau it is the number of growing polymer particles being kept constant, not the number of polymer particles. When the dose rate was changed while the polymerization came into the constant period, the polymerization rate and the molecular weight of the polymer varied with the dose rate. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 257–262, 1998     

Poly(propene-co-maleic acid) with lateral perester groups as initiator in the emulsion polymerization of styrene

The influence of the initiator structure on the reaction process was investigated. In addition to the initiator concentration, its molar mass and the content of perester groups in the single molecule are determining factors that influence the course of reaction. Quantitative relationships are shown. The initiator is bonded by grafting reactions on the surface of the latex particles. The grafted moiety is dependent on the initiator structure and reaction temperature. Latices with polydispersities lower than 1.1 are obtained. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2045–2054, 1999     

Coagulum formation and elimination in emulsion copolymerization of tribromostyrene with styrene

Coagulum formation in emulsion polymerization of tribromostyrene and also in its copolymerization with styrene has been shown to be due to thermal polymerization. The latter takes place in the monomer reservoirs, even in the absence of radical generating initiators, converting them into sticky particles which then form the undesired coagulum. The coagulum formation phenomenon can thus be remedied by reducing the thermal initiation level through a semi-batch emulsion polymerization method, by lowering the polymerization temperature, and reduction of the collision frequency of monomer/polymer particles.     

On the emulsion polymerization of styrene in the presence of a nonionic emulsifier

The batch emulsion polymerization kinetics of styrene (St) initiated by a water-soluble peroxodisulfate in the presence of a nonionic emulsifier was investigated. The polymerization rate versus the conversion curves showed two nonstationary rate intervals, two rate maxima, and Smith–Ewart Interval 2 (nondistinct). The rate of polymerization and number of nucleated polymer particles were proportional to the 1.4th and 2.4th powers, respectively, of the emulsifier concentration. Deviation from the micellar nucleation model was attributed to the low water solubility of the emulsifier, the low level of the micellar emulsifier, and the mixed modes of particle nucleation. In emulsion polymerizations with a low emulsifier concentration, the number of radicals per particle and particle size increased with increasing conversion, and the increase was more pronounced at a low conversion. By contrast, in emulsion polymerizations with a high emulsifier concentration, the number of radicals per particle decreased with increasing conversion. This is discussed in terms of the mixed models of particle nucleation, the gel effect, and the pseudobulk kinetics. The formation of monodisperse latex particles was attributed to coagulative nucleation and droplet nucleation for the polymerizations with low and high emulsifier concentrations, respectively. The effects of the continuous release of the emulsifier from nonmicellar aggregates and monomer droplets, the close-packing structure of the droplet surface, and the hydrophobic nature of the emulsifier on the emulsion polymerization of St are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4422–4431, 1999     

松香丙烯酸基二元单体与苯乙烯的共聚反应

以丙烯酸松香加成物(RA)与甲基丙烯酸-2-羟乙酯的酯化物(RAH)为二元单体,采用溶液聚合法制备了苯乙烯与RAH的共聚物.通过正交实验法研究了反应条件对RAH与苯乙烯共聚反应的影响.对正交实验的结果分析得出:在反应温度为105℃下,RAH与苯乙烯的质量比为1:2,引发剂的用量为单体质量的1.5%,反应时间为8小时,单体转化率最高,为85%;原料配比对共聚反应的影响最为显著,其次是反应温度和引发剂用量,反应时间的影响最小.通过红外光谱分析和核磁共振图谱分析表明成功合成了RAH与苯乙烯的共聚物,热重分析表明产物的热稳定性随单体中RAH比例的增加而增加.     

Effect of temperature on styrene emulsion polymerization in the presence of sodium dodecyl sulfate. II

The batch emulsion polymerization kinetics of styrene initiated by a water‐soluble peroxodisulfate at different temperatures in the presence of sodium dodecyl sulfate was investigated. The curves of the polymerization rate versus conversion show two distinct nonstationary‐rate intervals and a shoulder occurring at a high conversion, whereas the stationary‐rate interval is very short. The nonstationary‐state polymerization is discussed in terms of the long‐term particle‐nucleation period, the additional formation of radicals by thermal initiation, the depressed monomer‐droplet degradation, the elimination of charged radicals through aqueous‐phase termination, the relatively narrow particle‐size distribution and constant polydispersity index throughout the reaction, and a mixed mode of continuous particle nucleation. The maximum rate of polymerization (or the number of polymer particles nucleated) is proportional to the rate of initiation to the 0.27 power, which indicates lower nucleation efficiency as compared to classical emulsion polymerization. The low activation energy of polymerization is attributed to the small barrier for the entering radicals. The overall activation energy was controlled by the initiation and propagation steps. The high ratio of the absorption rate of radicals by latex particles to the formation rate of radicals in water can be attributed to the efficient entry of uncharged radicals and the additional formation of radicals by thermally induced initiation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1477–1486, 2000     

Contribution of steric and electrostatic repulsion forces to the stability of styrene latices copolymerized with acrylic acid

Acrylic acid (AA) is used in many emulsion polymerization formulations to improve the colloidal stability of the latex product. The improved stability originates from electrostatic repulsion complemented with steric repulsion. The strength of the electrostatic and steric repulsion forces in a styrene (S)/AA copolymer latex was investigated at different pH values, electrolyte concentrations, and temperatures. A comparison was made with an S homopolymer latex. Transmission electron microscopic pictures, combined with visual inspections, provided understanding of the mechanisms leading to coagulation in polystyrene (PS)/AA copolymer latices. Colloidal stability of the unswollen sodium dodecyl sulfate stabilized PS latex is based on electrostatic repulsion. Destabilization by sodium chloride resulted in aggregation. The acidic PS/AA latex remained stable against aggregation at high electrolyte concentrations because of steric repulsion. The acidic PS/AA latex showed a strong tendency to flocculate at increasing electrolyte concentrations. Flocculation was not observed for high‐pH PS/AA latices at high electrolyte concentrations. Steric repulsion of the acid PS/AA latex was lost at temperatures higher than the critical coagulation temperature (35 °C), and flocculation was followed by aggregation and coalescence. The high‐pH PS/AA latex was stable even at high electrolyte concentrations and temperatures up to 80 °C because of strong electrosteric stabilization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2985–2995, 2003     

An experimental investigation on the evolution of the molecular weight distribution in styrene emulsion polymerization

Styrene ab initio emulsion polymerizations were conducted at 70°C in an automated reaction calorimeter. Two polymerizations were performed, one above and the other below the critical micelle concentration (CMC) of the surfactant, thus ensuring differing polymerization kinetics between the two: the system below the CMC gave large particles that were expected to follow pseudobulk kinetics, while that above the CMC gave small particles that were expected to follow zero-one kinetics. The evolutions of the molecular weight distributions (MWDs) were characterized by removing samples periodically during the course of the reactions and analyzing with gel permeation chromatography. Interpretation of the data used average molecular weights, the GPC MWDs, and the number MWDs, as functions of conversion. It was found that all of the number MWDs (plotted as ln (number of polymer chains) vs. molecular weight of polymer chains) were concave-up at low molecular weights and become nearly linear at molecular weights (≥3−4 × 10⁶); this linearity is expected from theory. The slope of the high molecular weight region was consistent with theory for the dominant mode for chain stoppage: termination and transfer for the pseudobulk system and (predominantly) chain transfer to monomer for the zero-one system. The most likely explanation for the concavity of the number MWDs is a heterogeneity of radicals: some surface anchored with sulfate end groups and others (with hydrogen end groups arising from transfer to monomer and/or reentry) being more mobile. Thus, two types of termination are proposed: slow reaction-diffusion for the less mobile surface anchored chains, and rapid short-long (center of mass) termination for the more mobile hydrogen-terminated chains. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 989–1006, 1997