有机硅-丙烯酸酯聚合物乳液合成及粒径分析

通过种子乳液半连续法合成了有机硅改性丙烯酸酯聚合物乳液,并对其粒子形态及分布进行分析。结果表明:通过种子乳液半连续聚合工艺可制备出固含量42wt%,乳化剂含量4wt%(基于单体量)、窄分布纳米粒子的有机硅改性丙烯酸酯聚合物乳液。随反应进行,粒径分布变窄,平均粒径逐渐增大。随乳化剂中SDS与OP-10的摩尔比减少,粒径增大。     

P(MMA-M12-BPMA)乳液的合成及紫外吸收性能

以甲基丙烯酸甲酯(MMA)、可聚合乳化剂马来酸酐衍生物磺酸钠(M12)和可聚合紫外线吸收剂2-羟基-4-(3-甲基丙烯酰氧基-2-羟基丙氧基)苯甲酮(BPMA)为原料,采用乳液聚合方法制备了P(MMA-M12-BP-MA)共聚物乳液。通过转化率、红外光谱、以及紫外吸收光谱测定,分别研究了M12含量对聚合反应速率的影响、所得共聚产物的结构、以及共聚物乳液和共聚物紫外吸收特性。结果表明,随M12含量增大,聚合反应速率增加;BPMA含量增大有利于提高共聚物乳液和共聚物紫外吸收性能。     

丙烯酸酯纳米乳液的制备与表征

将甲基丙烯酸羟乙酯(HEMA)与甲基丙烯酸(MAA)或丙烯酸(AA)用作甲基丙烯酸甲酯(MMA)／丙烯酸丁酯(BA)乳液聚合体系的反应性助乳化剂，采用一种改进的微乳液聚合方法，合成了高单体／乳化剂比例(大于40：1)的聚丙烯酸酯纳米乳液．讨论了引发剂、乳化剂、助乳化别对乳胶粒大小和胶膜吸水率的影响，并对乳液的流体力学行为，共聚物的拉伸行为及耐水性等进行了研究．     

可聚合乳化剂制备纳米色料的形貌及其影响因素

以α-烯烃磺酸钠(AOS)为可聚合乳化剂、苯乙烯(St)为非极性单体、甲基丙烯酸甲酯(MMA)为极性单体、二乙烯基苯(DVB)为交联剂、十六烷(HD)为助稳定剂,通过细乳液聚合法制备了聚合物包覆蒽醌类染料的纳米色料。利用透射电子显微镜(TEM)、激光粒度仪(DLS)等研究了可聚合乳化剂、极性单体和交联剂的用量对纳米色料形貌的影响。结果表明:该纳米色料具有明显的核壳结构,且乳液的稳定性好。随着乳化剂用量的增加,粒子粒径变小;少量极性单体的加入有助于得到粒径分布较窄的核壳结构纳米粒子,交联剂和单体彼此极性的差异会导致粒子表面粗糙。以St为聚合单体,当DVB的质量小于St质量的30%时,能够得到结构规整的纳米粒子,超过30%时,纳米粒子表面不再光滑。而以MMA为聚合单体,当DVB的质量为MMA的8%~30%时,粒子表面均凹凸不平。     

苯乙烯-丙烯酸酯微乳液的合成研究

目前国内外许多专家学者积极研发低污染、低能耗、高性能的胶粘剂,以代替传统的毒性大、成本高、稳定性差的溶剂型胶粘剂[1]。苯乙烯-丙烯酸酯微乳液(苯-丙微乳液)是重要的胶粘剂之一。与常规乳液胶粘剂相比,它具有以下几个特点[2]:(1)是热力学稳定体系,可以自发形成;(2)分子粒     

MMA／BA／AA／HEMA无皂乳液体系的合成与性能表征

本文采用分步控浊结合种子人聚的新方法合成了ＭＭＡ／ＢＡ／ＡＡ／ＨＥＭＡ无皂乳液体系,并对其粒径、耐水性以及贮存稳定性进行了研究。实验结果表明,该方法合成的无皂体系不仅固含量较高,反应稳定性和贮存稳定性较好,而且具有优良的耐水性。     

可聚合乳化剂合成苯乙烯-丙烯酸丁酯-α-烯烃磺酸钠共聚物乳液

以工业原料α-烯烃磺酸钠(AOS)作为可聚合乳化剂,苯乙烯(St)和丙烯酸丁酯(BA)为单体,采用预乳化种子乳液聚合合成了St-BA-AOS共聚物乳液.通过测定AOS与两种单体的竞聚率确定了半连续加料法的聚合方式.探讨了单体的加料方式、反应温度、反应时间、AOS用量等工艺条件对胶乳的影响,获得了最佳聚合条件.IR,NMR和DSC测试结果分析表明:St,BA与AOS发生了自由基共聚反应,形成的P(St-BA-AOS)共聚物结构中含有磺酸基等亲水性基团有利于乳液的稳定.在此基础上考察了AOS用量对乳液的固含量及乳胶粒粒径等的影响.结果表明:随着AOS用量的增加,乳液的固含量增加、乳胶粒的平均粒径减少.当AOS含量为2%时乳液的固含量为45.01%,平均粒径为74 nm,粒径分布指数为0.08,玻璃化温度为23.17℃.TEM测试结果显示,用相同量的AOS代替十二烷基硫酸钠可得到粒径更小和粒径分布更为均匀的乳液体系.     

含氟/硅丙烯酸酯核壳型乳液的合成及性能

采用半连续种子乳液聚合法, 在十二烷基硫酸钠(SDS)/辛基苯基聚氧乙烯醚(TX-10)复合乳化剂的作用下, 合成了以丙烯酸丁酯(BA)为核, 以甲基丙烯酸甲酯(MMA)、甲基丙烯酸十二氟庚酯(DFHMA)、3-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPTMS)和甲基三甲氧基硅烷(MTMS)为壳的核壳型含氟/硅丙烯酸酯聚合物乳液. 利用FTIR, TEM, SEM-EDX和DSC等手段对乳液组成、乳胶粒子结构、膜表面及断面形态等进行了表征, 讨论了氟/硅含量对聚合物膜性能的影响. 结果表明, 核-壳粒子尺寸为20~30 nm, 乳液膜的性能与膜表面氟和硅的含量及相容性有较大的相关性, 当m(氟)∶m(硅单体)=3∶1时, 形成的膜均匀透明, 吸水率较低, 尺寸稳定性较好.     

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。     

阴离子型石蜡乳液的制备与表征

以固体切片石蜡为原料,硬脂酸为单一乳化剂,采用转相乳化(EIP)法制备了阴离子型石蜡乳液。实验结果表明,单一阴离子型乳化剂的乳化效果较好,可以得到平均粒径小(1μm左右)、多分散性低(多分散性指数2左右)的较稳定的石蜡乳液。通过单因素实验考察了乳化剂用量、乳化水用量、乳化时间、乳化温度等对石蜡乳液性能的影响,得出最佳工艺条件∶乳化剂用量7(wt)%、乳化水用量82(wt)%、乳化时间25min、乳化温度80℃。在此条件下,研究了加水方式、p H对石蜡乳液粒径的影响。少量多次的加水方式、p H=9.9制得的乳液平均粒径可达到0.62μm。     

Thermal stability of copolymers of vinyl acetate and methyl acrylate

The thermal degradation of a series of copolymers of vinyl acetate and methyl acrylate and the two homopolymers poly(vinyl acetate) and poly(methyl acrylate) obtained using Ce(IV) as initiator has been investigated using differential thermal analysis (DTA) and thermogravimetry (TGA) in dynamic nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The stability increases as the methyl acrylate content in the copolymer composition increases. The incorporation of 5 mol % of vinyl acetate in the copolymer produces a marked decrease in stability compared to the homopolymer poly(methyl acrylate). There is evidence for an intramolecular lactonization process in vinyl acetate—methyl acrylate copolymers.     

Emulsion terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate: Experimental results

A systematic study of the terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc) was conducted. In this stage of the study, batch emulsion terpolymerizations were performed in a 5 L stainless steel pilot plant reactor. The experiments were designed using a Bayesian (optimal) technique. The polymers produced were characterized for conversion, composition, molecular weight, and particle size. Conversion, terpolymer composition, number- and weight-average molecular weight, and average particle size results are discussed in light of the influence of seven factors and the interaction of these factors. The factors studied include monomer feed composition, initiator concentration, chain transfer agent concentration, impurity concentration, initiator type, emulsifier concentration, and temperature. A “two-stage rate” phenomenon, similar to that occurring in bulk co- and terpolymerization and emulsion copolymerization of acrylic/vinyl acetate systems was observed in the conversion, composition and molecular weight data. Furthermore, an interesting yet often ignored effect of impurities on emulsion polymerization kinetics was explained. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1659–1672, 1997     

Semicontinuous seeded emulsion copolymerization of vinyl acetate and methyl acrylate

The semicontinuous seeded emulsion copolymerization of vinyl acetate and methyl acrylate was investigated. The effect of type of process (starved process versus semi-starved process), type of feed (neat monomer addition versus monomer emulsion addition), amount of seed initially charged in the reactor, and feed rate on the time evolution of the overall conversion, copolymer composition, and polymer particle size was analyzed. It was found that, in the case of the starved process, both monomers, but mainly vinyl acetate, accumulated in the reactor. The preferential accumulation of vinyle acetate resulted in a drift of the copolymer composition. Both monomers accumulation and copolymer composition drift were reduced by increasing the amount of seed initially charged in the reactor and by decreasing the feed rate. For the semi-starved process, it was found that a vinyl aceatate rich copolymer was formed when a low methyl acrylate feed was used, whereas a methyl acrylate rich copolymer was obtained at high methyl acrylate feed rates. For both starved process and semi-starved process, the total number of polymer particles, after an initial increase, reached a plateau value which was the same in all of the experiments carried out. These results were analyzed by means of a mathematical model developed for this system.     

Synthesis and characterization of fluorescently labelled poly(vinyl acetate) particles

Nonaqueous dispersions of poly(vinyl acetate) particles stabilized with poly(2-ethylhexyl methacrylate) and labelled with fluorescent dyes in the core and stabilizer polymer phases were prepared. The materials were characterized using a broad range of techniques (NMR, UV, and fluorescence spectroscopy. GPC, particle sizing, and DSC). The data show that dispersion polymerization of vinyl acetate in the presence of stabilizers containing certain fluorescent dye derivatives, instead of unlabelled stabilizer, results in changes in the mean particle size, size distribution, composition, and molecular weights of the colloidal polymer particles. It was found that increasing the amounts of fluorescent groups in the stabilizer resulted in smaller mean particle sizes and larger amounts of irreversibly attached stabilizer. When the average number of labels in stabilizer exceeded one per chain, a new ultra-high molecular weight polymer fraction appeared. The fluorescence spectra for several of these materials are reported. We describe how fluorescence decay curves can be used to assess block formation and local phase separation in particles labelled with phenanthrene groups. These materials are intended to be used for more detailed studies by fluorescence spectroscopy. Those results will be published in due course.     

One- and two-dimensional NMR studies of methyl acrylate/vinyl acetate/N-vinyl carbazole terpolymers

Terpolymers of methyl acrylate/vinyl acetate/N-vinyl carbazole (M/A/C) with different compositions were synthesized by solution polymerization using AIBN as an initiator. Composition of terpolymers was determined from quantitative ¹³C{¹H} NMR spectrum. Two-dimensional heteronuclear single quantum correlation (HSQC) and total correlated spectroscopy (TOCSY) were used to assign the methylene and methine carbon resonances by analyzing two and three bond order couplings. Various resonance signals were assigned to different compositional and configurational sequences with the help of one- and two-dimensional NMR spectra. Three and four bond order coupling between carbonyl carbon and other neighboring protons have been investigated with the help of 2D heteronuclear multiple bond correlation (HMBC) spectra. The complex and overlapped ¹H NMR spectrum of terpolymer was analyzed completely with the help of 2D HSQC and TOCSY spectra.     

Copolymerization of methyl acrylate and vinyl acetate catalyzed by ethylaluminium chlorides

The copolymerization of vinyl acetate with methyl acrylate in the presence of Et₂AlCl, Et_1.5AlCl_1.5, and Et₂AlCl-benzoyl peroxide systems has been investigated. The influence of monomer ratios and organoaluminium compound concentration on the copolymer yield and composition have been determined and discussed. The monomer sequences distribution has been studied by means of ¹³C-NMR. It was found that organoaluminium compounds in the studied systems catalyze not only the alternating copolymerization, but also the homopropagation of both monomers. An alternating copolymer was obtained in reactions carried out at ?78°C, when a large excess of vinyl acetate was used in the monomer feed.     

Shrinkability of ethylene vinyl acetate/polyurethane blends and their characterization

Heat shrinkability of the polymer, which depends on the elastic memory, is being utilized in various applications, mainly in the field of encapsulation. The elastic memory is introduced into the system in the form of an elastomeric phase. Here the blends of ethylene vinyl acetate and polyurethane were studied with reference to their shrinkability, introducing crosslinking in both the phases. It is found that with increase in elastomer content the shrinkage increased to a certain level and then decreased. With increase in cure time shrinkage is decreased. It is seen that high‐temperature (HT) stretched samples showed higher shrinkage than room temperature (RT) stretched one. Generally, the crystallinity of the HT stretched sample is higher than that of low‐temperature stretched sample, which is again higher than that of original sample. From high temperature differential scanning calorimetry it is found that with increase in PU content stability towards oxygen is increased and further high temperature processing decreases the initial degradation temperature but enhances the rate of degradation. From scanning electron microscopy it is seen that an HT stretched sample is more elongated than an RT stretched one. Copyright © 2000 John Wiley & Sons, Ltd.     

Evolution of multimodal particle size distribution in vinyl acetate/butyl acrylate emulsion copolymerizations

This article presents a study on the engineering of multimodal distributions in semibatch emulsion polymerizations with nonionic surfactants. Various methods of producing multimodal distributions are demonstrated, and the sensitivity of the process to the properties of the reagents are analyzed. A test‐bed emulsion polymerization system, equipped with instrumentation to measure particle size distribution (capillary hydrodynamic fractionator) and monomer conversion (densitometer and flow meters), is used for this purpose. The process is monitored and controlled with an industrial distributed control system, which enables the automated operation of the process through sequential or logic controllers operating over lower level proportional integral derivative controllers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2232–2249, 2003