用聚合型乳化剂制备反相乳液的研究

以丙烯酸钠水溶液为水相,煤油为油相,Span80甲基丙烯酸酯(Span80 MA)聚合型乳化剂、Span80和Twen80为复配乳化剂,制备反相乳液。计算聚合型乳化剂(Span80MA)的HLB值,考察了乳化剂浓度、水相体积分数φ及单体浓度对乳液类型及稳定性的影响规律。结果显示:HLB(Span80MA)=4.0;形成稳定的反相乳液理想条件为:Span80MA∶Span80∶Twen80=0.7∶0.5∶0.2;乳化剂浓度为7%;φ=50%;单体浓度为2.0～3.0 mol/L。     

含聚合型乳化剂反相乳液体系的稳定性研究

以煤油为油相,丙烯酸钠水溶液为水相,自制的非离子聚合型乳化剂-Span80丙烯酸酯(Span80AA)、Span80和Twen80组成复合乳化剂,制备反相乳液。计算出Span80AA的HLB值,考察了乳化剂浓度、水相体积分数Φ及单体浓度对乳液类型及稳定性的影响。结果表明:HLB(Span80AA)=2.709;Span80AA、Span80和Twen80的最佳质量比为0.8∶0.3∶0.1。形成稳定的反相乳液理想条件是:复合乳化剂质量分数为6%~8%;Φ<57%;单体浓度为2.0~3.5 mol/L。     

丙烯酰胺反相微乳液稳定性影响因素的研究

使用复配乳化剂,以液态烷烃为连续相,丙烯酰胺溶液为分散相制备均匀的油包水(W/O)型微乳液。通过测定体系电导率及观察稳定性,以水相的最大增溶度为指标,研究了连续相的种类、乳化剂复配、丙烯酰胺(AM)单体浓度、电解质浓度对微乳液体系稳定性的影响。结果表明:以异构烷烃Isopar M为连续相,乳化剂Span80/OP-10复配且当复配乳化剂中Span80含量占80%时,体系对水相增溶量最大;提高AM浓度、加入适量电解质Na Ac,都会增强微乳液的稳定性;电解质的加入还会提高乳化剂的最佳HLB值。     

丙烯酸酯反相微乳液聚合动力学

对以甲基丙烯酸甲酯/丙烯酸丁酯混合单体为连续油相、十二烷基硫酸钠为乳化剂、丙烯酸为反应性助乳化剂构建的反相微乳液体系,以偶氮二异丁腈引发微乳液聚合,系统考察了引发剂浓度、乳化剂浓度、助乳化剂浓度、水相质量分数及反应温度对表观聚合速率的影响.讨论结果表明,微乳液聚合中液滴成核相当重要,聚合速率随体系中引发剂浓度、丙烯酸浓度、水相质量分数及聚合温度的升高而加快,随体系中乳化剂浓度的增大而降低,并得出动力学关系式,且聚合反应表观活化能为114 kJ&#8226;mol^-1.     

AM/NaAA双水相共聚反应合成HPAM研究

以丙烯酰胺与丙烯酸钠为原料,在聚乙二醇水溶液中进行双水相共聚合反应。探讨了分散介质对双水相共聚合反应的影响,考察了共聚单体摩尔配比、共聚单体与分散介质摩尔比、引发体系、聚合温度、乳化剂对HPAM-PEG-水乳液体系稳定性、单体残留量以及HPAM特性粘数的影响。研究发现共聚单体与分散介质摩尔比为0.125～1.0,聚合温度为45℃以上时才能得到相对稳定的聚合物双水相乳液体系,所得水乳液体系稳定性长达15个月以上。采用Span80和Tween80复配作为乳化剂效果好,水乳液体系的最佳HLB值为9.65。     

反相微乳聚合制备聚合物纳米粒子

采用正辛烷做连续相,以Span80和Tween60为复合乳化剂,过硫酸铵-亚硫酸氢钠为氧化还原引发剂体系,通过反相微乳聚合制备丙烯酰胺-丙烯酸钠纳米粒子.研究了乳化剂、单体、引发剂配比及用量和温度等因素对聚合的影响.在反应温度为30 ℃,乳化剂浓度为油相质量的12 %～14 %,单体浓度为水相质量的35 %～40 %,引发剂浓度为单体质量的0.05 %～0.07 %时,得到稳定透明的微乳液.经扫描及透射电镜分析,所得共聚物的粒径为40～60 nm之间,粒子均匀分布的规则球形.     

超声预乳化环硅氧烷乳液共聚合

以十二烷基苯磺酸钠(SDBS)为乳化剂、硫酸为催化剂,将八甲基环四硅氧烷(D4)与四甲基四乙烯基环四硅氧烷(D4^Vi)进行正离子开环共聚,制备了聚硅氧烷乳液。比较了超声预乳化方式和机械搅拌预乳化方式对预乳液粒径分布、乳液粒径分布及聚合反应动力学的影响,考察了单体质量比、聚合温度、催化剂浓度和乳化剂浓度对聚合动力学及乳液粒径分布的影响。结果表明,超声预乳化聚合中同时存在单体小液滴成核和胶束成核2种机理,超声预乳液稳定性较好,平均粒径为180nm,最终转化率可达90％左右;当聚合温度为80℃、SDBS质量分数为l％、硫酸质量分数为3％时,可以制得稳定的聚硅氧烷乳液。     

丙烯酰胺反相细乳液聚合

采用反相细乳液法,以白油为连续相,失水山梨醇单油酸酯/聚氧乙烯失水山梨醇单油酸酯为乳化剂,一种聚合物型乳化剂(聚异丁烯琥珀酸酯与山梨醇油酸酯的混合物)作为助稳定剂,通过正交实验确立了基本乳液体系,考察了微乳化工艺中转速变化、乳化剂体系组成、浓度及单体含量对聚合产物稳定性的影响,并研究了不同单体浓度和聚合时间等聚合工艺对微球粒径及分布的影响。结果表明,复合乳化剂含量为3.0%,转速为10 000 r/min下乳化20 min,在单体浓度55%,亲水疏水平衡值(HLB值)为5.5,采用氧化还原引发体系,聚合时间为6 h时,可以得到固含量35%以上、粒径数百纳米的长期稳定的亚微米级聚丙烯酰胺微球乳液。     

高分子量乳液型减阻剂的合成及评价

采用反相乳液聚合方法制备了一种用于滑溜水压裂液的高分子量乳液型减阻剂。考察了复合乳化剂对乳液减阻剂稳定性的影响,研究了乳化剂含量、聚合温度和引发剂浓度对减阻剂分子量的影响,分析了减阻剂的分子结构、乳液粒径大小分布和减阻效率。实验结果表明:m(Span80)∶m(Tween80)∶m(OP-10)=20∶2∶1时乳液最为稳定;在18℃、乳化剂在油相中质量分数为15%、引发剂质量为单体质量的0.015%时,得到分子量达1.8×107g/mol的稳定乳液型减阻剂。在清水中加入0.05%的减阻剂,减阻率高达62.8%。     

乳化剂对丙烯酸酯乳液及涂膜性能的影响

采用种子预乳化半连续法工艺合成丙烯酸酯乳液,分析对比了乳化剂结构类型、乳化剂用量、乳化剂加入方式及种子液添加量对丙烯酸酯乳液及涂膜性能的影响。研究结果表明:采用阴/非离子复配型乳化剂,且主乳化剂为阴离子反应型乳化剂时,乳液的聚合稳定性和单体转化率较高。     

RADICAL DESORPTION IN EMULSION POLYMERIZATION OF VINYL ACETATE

In the present paper a model equation for calculating the radical desorption rate constant,k_0,in the emulsion polymerization of vinyl acetate was suggested and the various parameters forevaluating k_0 were determined.Effects of reaction temperature,emulsifier concentration,initiator con-centration,monomer conversion and phase ratio on k_0 were studied.It indicates that the desorptionof radicals from latex particles to aqueous phase must be taken into account in the modelling ofemulsion polymerization for the monomers with higher hydrophilicity such as vinyl acetate.     

The inverse emulsion polymerization of acrylamide with pentaerythritolmyristate as emulsifier. 1. Experimental studies

The inverse emulsion polymerization of aqueous acrylamide solutions in isooctane as dispersing media with the emulsifier pentaerythritolmyristate and an oil-soluble azo initiator was studied, particularly with respect to the influence of the chemically pure emulsifier. In this free radical polymerization, a water-in-oil emulsion with droplet sizes around 10μm is converted into a latex with average particle diameters between 80 and 200nm containing a polymer with molar masses up to 16×10⁶gmol^-1 Kinetic data were measured by adiabatic as well as by isothermal calorimetry. The influences of various parameters on polymerization kinetics, particle numbers and molar mass averages were studied. Experimental results show a positive influence of the emulsifier concentration on the reaction rate and indicate the dominance of a bimolecular termination re-action with respect to the polymer radicals above a certain initiator concentration. © 1998 SCI.     

DMDAAC-AM反相微乳液体系的制备及聚合

以非离子表面活性剂Span-80和OP-10为复配乳化体系,煤油为油相,二甲基二烯丙基氯化铵(DMDAAC)和丙烯酰胺(AM)为单体,采用电导法和目测法相结合的方式,考察了乳化剂的亲水疏水平衡(HLB)值、水相单体浓度和配比、电解质、温度和乳化剂浓度等因素对体系稳定性和水相增溶量的影响. 结果表明,HLB为7.70、水溶液中单体浓度为60%、DMDAAC/AM摩尔比为0.2、水相中甲酸钠浓度为1.25%时,体系的电导率变化较为平稳,增溶水量也较多,温度的升高对体系的稳定性有反作用. 对该体系进行聚合,可得到澄清稳定的聚合物微胶乳. 比较聚合前后体系的粒径分布发现,聚合物粒子的体积明显增大,表明聚合过程符合单体扩散和胶束碰撞两种机理.     

P(AM-DADMAC)的反相乳液聚合及其表征

利用反相乳液聚合法制备了阳离子共聚物P(AM-DADMAC),考察了乳化剂、分散介质、引发剂、单体浓度等因素对乳液体系稳定性和共聚物特性粘度的影响。结果表明:以Span80和Tween80为复合乳化剂且浓度为4%、煤油为分散介质、油水体积比为0.5、Va-044为引发剂且浓度为0.08%～0.1%、水相单体浓度为45%时,反相乳液聚合体系稳定,且能得到特性粘度较大的阳离子共聚物。利用红外谱图证实了共聚物P(AM-DADMAC)的结构。电镜照片显示,胶体颗粒为球形,尺寸在1～9μm之间。     

反相乳液聚合法合成阳离子聚丙烯酰胺的研究

以液体石蜡为连续相，选择Span80-Tween80的复合乳化剂，进行了AM—DMC的反相共聚合反应，研究了温度、单体配比、乳化剂质量分数对聚合物性能的影响。     

Dispersion Polymerization of Styrene by Initiation Within Monomer Phase with Lauroyl Peroxide

Dispersion polymerization kinetics of styrene was investigated in this study. A monomer phase soluble initiator, namely lauroyl peroxide, and a water phase soluble emulsifier, namely sodium dodecyl sulfate, were used. the polymerizations were carried out in a magnetic drive, sealed, cylindrical polymerization reactor, in nitrogen atmosphere. Two different fatty alcohols, cetyl and lauryl alcohols, were tried as particle size increasing agents. the effects of initiator, emulsifier concentrations, monomer/water ratio, and the weight ratio of particle size increasing agent to emulsifier on the total monomer conversion, average size, and size distribution of the large latex particles were studied. the agglomeration conditions were tested by changing the polymerization temperature, initiator, and emulsifier concentrations. the results indicated that the polymerization rate and the average size of the latex increased with increasing emulsifier concentration. the average size of the latex was also increased with increasing initiator concentration. the use of cetyl alcohol in the presence of emulsifier resulted in an appreciable increase in the polymerization rate and in the average size of the latex. the effect of fatty alcohols on the polymerization rate in the dispersion polymerization system was completely different than that in the swollen emulsion polymerization. the agglomeration of the large latex particles was increased with decreasing emulsifier and increasing initiator concentrations.     

A new polymerization method and kinetics for acrylamide: Aqueous two‐phase polymerization

The concept of aqueous two‐phase polymerization and a new polymerization method for the preparation of water‐soluble polymers are presented. The phase diagram of poly(acrylamide) (PAAm)‐poly (ethylene glycol) (PEG)‐water two‐phase system was measured by the gel permeation chromatography (GPC). The aqueous two‐phase of PAAm‐PEG‐water system can be easily formed. The critical concentration of phase separation was affected by the molecular weight of PEG. The aqueous two‐phase polymerization of acrylamide (AAm) has been successfully carried out in the presence of PEG by using ammonium persulfate (APS) as the initiator. The polymerization behaviors with varying concentration of AAm, initiator and PEG, the polymerization temperature, the molecular weight of PEG, and emulsifier types were investigated. The activation energy of aqueous two‐phase polymerization of AAm was 132.3 kJ/mol. The relationship of initial polymerization rate (R_p0) with APS and AAm concentrations was R_p0 ∝ [APS]^0.72 [AAm]^1.28. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009