Influence of Particle Nucleation in Pressure Sensitive Adhesive Properties: Miniemulsion versus Emulsion Polymerization

Miniemulsion polymerization is a promising approach to produce and tailor pressure sensitive adhesives (PSAs). In this paper, a systematic comparison of the adhesive properties of latexes produced by miniemulsion and conventional emulsion polymerization is presented. Specifically, the influence of the total surfactant concentration, chain transfer agent concentration and chemical composition on the final adhesive properties of the polymer 2-ethyl hexyl acrylate/methyl methacrylate/acrylic acid was discerned using a 2³ factorial design for each polymerization method. In addition to the adhesive properties (i.e., loop tack, peel strength and shear strength), molecular weight distribution, particle size distribution (PSD) and glass transition temperature were analyzed. The results show that under the conditions used in this work, it is possible to produce PSAs using miniemulsion polymerization, a process wherein monomer droplet nucleation is the dominant particle nucleation mechanism. The use of a miniemulsion polymerization process, as opposed to the conventional emulsion technique, produced several differences such as larger particles sizes and narrower molecular weight distributions. Focusing on the PSA films that exhibited adhesive rather than cohesive failure, the PSA films generated via miniemulsion polymerization displayed higher values of loop tack and peel strength compared to those produced via conventional emulsion polymerization. Shear strength results were strongly dependent on the amount of gel content and sol molecular weight for both cases.     

SEED SEMICONTINUOUS EMULSION MULTI-COPOLYMERIZATION OF (METH) ACRYLATES WITH HIGH-SOLID CONTENT: EFFECT OF THE OPERATION CONDITIONS

The seeded semicontinuous emulsion multi-copolymerization of butyl acrylate (BA),2-ethylhexyl acrylate (2EHA), methyl methacrylate (MMA), 2-hydroxyl propyl acrylate(HOPA) and acrylic acid (AA) was used to prepare the acrylic latexes with high-solidcontent. The effects of monomer emulsion feed rates (R_a) and (R/E)_E values, the ratio ofemulsifier amount between the initial charge (R) and the addition monomer emulsion (E),on the polymerization reaction features, the viscosities, surface tensions,particle sizes andparticle sizes distributions of latexes,T_g and the insoluble fractions of films, the 180° peelstrength, tack and holding power of pressure-sensitive adhesive (PSA) tapes, preparedfrom the latexes, were studied. Experimental study shows that the grafting and cross-linking fraction in the PSA tapes must be controlled within a suitable range to keep thebalance of the 180° peel strength, tack and holding power.     

High-Solids Content Waterborne Polymer-Clay Nanocomposites

Summary: Waterborne polymer clay nanocomposites (WPCN) were prepared by emulsion and miniemulsion copolymerization of butyl acrylate and methyl methacrylate with enhanced mechanical, thermal and barrier properties for coating applications. Emulsion polymerization was used to synthesize WPCN using pristine Na-MMT (sodium montmorillonite) and miniemulsion polymerization to prepare the WPCNs when the pristine clay was organically modified and hence its incorporation into the polymerization loci was not guaranteed by the conventional emulsion polymerization technique. Both techniques allowed preparing stable nanocomposite latexes of BA/MMA copolymers with partially exfoliated morphologies as demonstrated by wide X-ray difraction (WAXD) and transmission electron microscope (TEM) measurements. Furthermore, latexes with solids contents up to 45 wt% and manageable viscosities were prepared for the first time using seeded semibatch emulsion polymerization.     

Modification of Adhesive and Latex Properties for Starch Nanoparticle‐Based Pressure Sensitive Adhesives

Starch nanoparticle (SNP)‐based pressure sensitive adhesives (PSAs) with core‐shell particle morphology (starch nanoparticle core/acrylic polymer shell) are produced via seeded, semi‐batch emulsion polymerization at 15 wt% SNP loading (relative to total polymer weight) and 40 wt% latex solids. Crosslinker and chain transfer agent (CTA) are introduced to the acrylic shell polymer formulation at a range of concentrations according to a 3² factorial design to tailor the latex and adhesive properties of SNP‐based latexes. The crosslinker and CTA show no significant effect on polymerization kinetics, particle size, and viscosity. Latex gel content is predicted using an empirical model, which is a function of crosslinker and CTA concentration. Both the gel content and glass transition temperature strongly affect the adhesive properties (tack, peel strength, and shear strength) of the SNP‐based latex films. 3D response surfaces for the adhesive properties are constructed to facilitate the design of SNP‐based PSAs with desired properties.     

离子型表面活性单体存在下的MMA/BA乳液聚合(Ⅰ)——表面活性单体的合成及其(共)聚合活性

合成了两种离子型表面活性单体(Surfmer)磺化-十二醇-烯丙基甘油-丁二酸酯钠盐(ZC-L)和磺化-十二醇-甲基丙烯酰甘油-丁二酸酯钠盐(ZD-L).着重研究了ZC-L的结构、表面张力行为、均聚及共聚能力.实验结果表明,不同Surfmer用量以及不同固含量下,MMA/BA/Surfmer,MMA/Surfmer及BA/Surfmer共聚乳液的表面张力较高,说明Surfmer已通过共聚结合在乳胶粒上,乳液中残留甚少.对MMA/BA体系,ZC-L的共聚性能比ZD-L好.     

单体极性对甲基丙烯酸甲酯/丙烯酸丁酯/甲基丙烯酸钠无皂乳液共聚合的影响

研究了少量甲基丙烯酸钠（ＮａＭＡ）存在下单体极性对甲基丙烯酸甲酯（ＭＭＡ）／丙烯酸丁酯（ＢＡ）无皂乳液共聚合的影响．单体极性降低，使粒径减小、聚合速率提高、乳液表面张力和粘度降低、粒子表面电荷密度增大、聚合物分子量提高．ＭＭＡ／ＮａＭＡ无皂乳液聚合物只呈现一个玻璃化温度Ｔｇ，ＢＡ／ＮａＭＡ无皂乳液聚合物呈现两个Ｔｇ，ＭＭＡ／ＢＡ比为２∶１～１∶２的ＭＭＡ／ＢＡ／ＮａＭＡ无皂乳液聚合物呈现四个Ｔｇ，这是由于粒子外面相对富含ＯＳＯ－３和ＣＯＯ－基聚合物的亚层溶解了较多的水，使ＢＡ向粒子中心扩散，ＭＭＡ向外扩散，造成组成差异和相分离而引起的．     

Influence of hydrophobic monomers on secondary nucleation of hydroxyl‐functionalized latexes

The influence of butyl acrylate (BA) and methyl methacrylate (MMA) on hydroxyl functionalized latexes was investigated. The hydrophobicity of the monomer feed was varied via the BA/MMA ratio. In addition to monitoring the effect of hydrophobic monomer feed on secondary nucleation, the polymerization kinetics and final latex properties were also obtained for comparison. Five different BA to MMA molar ratios were combined with five 2‐hydroxyethyl methacrylate (HEMA) concentrations (0, 10, 20, 30 and 40 mol% in monomer composition). All latexes were synthesized through seeded semibatch emulsion polymerization process. Particle size distributions and average particle sizes of the latexes were determined by dynamic light scattering (DLS) and qualitatively compared with transmission electron microscope (TEM) images. The BA to MMA ratio significantly influences the boundary HEMA concentration at which homogeneous secondary nucleation occurs. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2190–2202     

The Effect of Polymer Microstructure and Thermal Post-Treatment on Latex-Based Pressure Sensitive Adhesive Performance

Summary: Butyl acrylate/acrylic acid/2-hydroxyl methacrylate (BA/AA/HEMA, weight ratio: 96/2/2) latexes were produced via starved seeded semi-batch emulsion polymerization. The microstructure of the latex polymers was controlled by varying the amount of chain transfer agent (1-dodecanethiol). The latexes were characterized for gel content, M_c (molecular weight between two adjacent cross-linking points), M_w (molecular weight of sol polymers) and M_e (molecular weight between entanglements). From these latexes, PSA films were cast, dried, conditioned and then thermally post-treated at 120 °C to react the carboxyl and hydroxyl groups from the AA and HEMA units. Tack, peel strength and shear strength of the PSA films were then measured. The thermal post-treatment was shown to be an effective way to improve latex-based PSA performance. The effectiveness of the post-treatment was observed to depend on the polymer microstructure (M_c relative to M_e relative to M_w) of the untreated latex-based PSAs and on the gel content.     

具有核壳结构磁性复合微球的制备与表征

采用两步法制备了具有核壳结构的Fe3O4/P(MMA/DVB)(core)-P(St/GMA/DVB)(shell)磁性复合微球.首先,用改进的细乳液聚合制备了Fe3O4/P(MMA/DVB)微球;然后,加入总量不同的苯乙烯(St)、甲基丙烯酸缩水甘油酯(GMA)和二乙烯基苯(DVB),通过种子乳液聚合,制备了不同磁含量的核壳结构的磁性复合微球.分别用X-射线衍射(XRD)、高倍透射电镜(HR-TEM)、热重分析(TGA)、振动样品磁力计(VSM)等手段对磁性微球的性能进行了表征.实验结果表明,Fe3O4/P(MMA/DVB)微球的磁含量为84 wt%;通过改变加入壳层单体的量,核壳复合微球的磁含量可控在20 wt%~76 wt%之间.该微球具有超顺磁性,相应的饱和磁化强度为12~50Am2/kg.     

离子型共聚单体用于高固含量无皂乳液聚合的研究——甲基丙烯酸异丁酯/甲基丙烯酸甲酯/丙烯酸丁酯无皂乳液聚合体系

该文采用自行合成的一种带亲水性磺酸离子基团及羟基的可共聚单体 3 烯丙氧基 2 羟基丙磺酸钠(AHPS)用于甲基丙烯酸异丁酯 /甲基丙烯酸甲酯 /丙烯酸丁酯 (IBMA/MMA/BA)无皂乳液聚合体系 .对乳胶粒粒径大小、乳液流体力学行为、共聚物的动态力学性质、拉伸行为及耐水性进行了研究 ,并对乳胶粒的成核机理进行了探讨 .实验结果表明 ,带亲水性离子基团可共聚单体AHPS的加入可获得 0 6μm左右的乳胶粒 ,乳液固含量可达 60 % ,表现粘度测定结果表明乳液呈Bingham流体 .三元共聚物在动态粘弹谱图上只出现单一的玻璃化转变温度峰 ,是完全的无规共聚物 ,拉伸强度明显大于常规乳液聚合方法得到的聚合物 ,耐水性也得到显著提高 .     

含氢聚甲基硅氧烷/丙烯酸丁酯/羟甲基丙烯酰胺复合乳液的研究——原料配比对乳液及胶膜性能的影响

采用含氢聚甲基硅氧烷（ＰＨＭＳ）与丙烯酸酯类单体进行接枝共聚，制得兼具二者优异性能的新型ＰＨＭＳ／丙烯酸丁酯（ＢＡ）／羟甲基丙烯酰胺（ＮＭＡ）复合聚合物乳液．讨论了ＰＨＭＳ、ＮＭＡ和引发剂用量对该复合乳液的聚合反应转化率、稳定性及粘度的影响．采用透射电子显微镜和粒度测试仪对不同反应条件下制备的乳液的粒度进行了测定．同时对聚合反应的机理、产物的结构及胶膜性能作了考察．结果表明：通过乳液聚合，得到了ＰＨＭＳ／ＢＡ／ＮＭＡ共聚物，控制ＰＨＭＳ、ＮＭＡ、引发剂等用量可制得粒度和粘度适中，具有较高转化率的稳定ＰＨＭＳ／ＢＡ／ＮＭＡ复合聚合物乳液，该乳液所制得的胶膜具有优良的性能     

HIGH SOLIDS-CONTENT NANOSIZE POLYMER LATEXES MADE BY A MODIFIED EMULSION COPOLYMERIZATION

Polymer nanoparticles were prepared in the methyl methacrylate (MMA)/buty lmethacrylate (BA) emulsion copolymerization process by a modified microemulsion copolymerization method. 2-Hydroxyethyl methacrylate(HEMA), acrylate (AA) and methyl acrylate (MAA) were used as reactive cosurfactants. With this process high polymer: surfactant weight ratios (40:1 or greater),relatively concentrated (～30wt. %) latexes and small (～60nm) particle diameters were obtained.Properties of the latexes were characterized by TEM, DSC, dynamic light scattering, and IR spectroscopy.     

HIGH SOLIDS-CONTENT NANOSIZE POLYMER LATEXES MADE BY A MODIFIED EMULSION COPOLYMERIZATION

1.INTRODUCTIONSince1980,agreatdealofresearchinteresthasbeendevotedtomicroemulsionpolymerization[1~10].Amicroemulsionmaybedefinedasthermodynamicallystableandopticallytransparentdispersioncomposedbywater,oilandsurfactant;inmanycasesacosurfactantisrequired.Microemulsionpolymerizationprocesscanyieldstablepolymerlatexeswithparticlesizeofabout10nmto100nm.However,therearetwomajordrawbacks,whichhavelimitedtheapplicationsofmicroemulsionpolymerization:(1)highsurfactantconcentration(upto20wt.%ofthet…     

Synthesis of poly(vinylidene chloride)-based composite latexes by emulsion polymerization from epoxy functional seeds for improved thermal stability

Poly(glycidyl methacrylate-co-butyl methacrylate)/poly(vinylidene chloride-co-methyl acrylate) (poly(GMA-co-BMA)/poly(VDC-co-MA)) composite latexes have been successfully synthesized via a two-stage emulsion polymerization process. In a first step, emulsion copolymerization of GMA and BMA was carried out in optimized conditions (low temperature, neutral pH, starved-feed conditions) to both limit the hydrolysis of epoxy groups and obtain small particle size (typically 30-50 nm size range). Composite latexes were then obtained by a second-stage seeded copolymerization of VDC and MA in the presence of tetrasodium pyrophosphate to control the pH and reach high molecular weight, leading to partial encapsulation of the seed particles (snow-man morphology, in agreement with theoretical expectations). Thermogravimetric analyses performed on the resulting composite particles showed that the epoxy-functionalized seed polymer behaved as an efficient thermal stabilizer of PVDC.     

高固含量低粘度P(MMA/BA/AA)乳液的制备及性能研究

先利用半连续种子乳液聚合法制备固含量为50%,粒径480nm的单分散甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)与丙烯酸(AA)的共聚物种子乳液;然后以上述种子乳液为介质,十二烷基硫酸钠为乳化剂,碳酸氢钠为缓冲剂,过硫酸铵为引发剂制备固含量72%,乳胶粒具有二元分布特征的高固含量、低粘度稳定乳液:其中大乳胶粒径500～600nm,小乳胶粒径约80nm.所得乳液中乳化剂总含量为聚合物质量的2.1%;粘度在剪切速率为21s-1时为400mPa·s.另外,相对于常规乳液,所制备高固含量乳液胶膜具有更好的光泽度.     

Emulsion polymerization of vinyl acetate using a polymerizable surfactant. II. Polymerization mechanism

The mechanism of growth of latex particles in the emulsion polymerization of vinyl acetate using a polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (TREM LF-40; Henkel) was investigated. Both the aqueous phase and the particle/water interface were found to be loci for the copolymerization of TREM LF-40 with vinyl acetate. Competitive growth experiments using TREM LF-40 and its nonpolymerizable derivative were conducted to separate the effects of aqueous phase and particle surface. Particle size analysis of the seeded and unseeded polymerizations coupled with kinetic results suggested that the reactions at the particle/water interface are more important and that the particle size of the latexes is a key parameter controlling the polymerization rate through copolymerization and chain transfer to the polymerizable surfactant at the particle surface. A decrease in particle size lead to an increase in the amount of TREM LF-40 polymerized at the particle surface and to a decrease in polymerization rate. © 1992 John Wiley & Sons, Inc.     

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．     

In Situ Semibatch Emulsion Polymerization of 2‐Ethyl Hexyl Acrylate/n‐Butyl Acrylate/Methyl Methacrylate/Cellulose Nanocrystal Nanocomposites for Adhesive Applications

Cellulose nanocrystals (CNCs) are safe, “green,” hydrophilic nanoparticles. CNCs are added in situ during a semibatch 2‐ethyl hexyl acrylate (EHA)/n‐butyl acrylate (BA)/methyl methacrylate (MMA) emulsion polymerization. As EHA is a more hydrophobic monomer, manipulation of the monomer feed composition allows for the evaluation of the effect of hydrophobicity on CNC distribution in the nanocomposite and ultimately on adhesive properties. The adhesive properties (loop tack, peel strength, and shear strength) of three different EHA/BA/MMA latex formulations are shown to simultaneously improve with increasing CNC loading. However, the hydrophobicity of the EHA leads to a nonuniform distribution of CNCs in the latex films. Comparison of the in situ polymerized nanocomposites to their blended counterparts is also made.     

表面活性单体存在下的MMA／BA乳液共聚合（Ⅱ）：聚合动力？…

研究了表面活性单体「磺化－十二醇－烯丙基甘油－丁二酸酯钠盐（ＺＣ－Ｌ）」的用量对ＭＭＡ／ＢＡ／ＺＣ－Ｌ乳液聚合速率和粒径的影响,用Ｃｏｒｌｔｉｒ ＬＳ２３０型激光粒径分析仪测定聚合过程中乳液的粒径和粒径分布变化,并与ＭＭＡ／ＢＡ无皂乳液聚合及十二烷基苯磺酸钠存在下的ＭＭＡ／ＢＡ乳液聚合作了比较。「ＺＣ－Ｌ」〈ＣＭＣ时,成核机理为均相成核机理,乳胶粒需依靠粒子间的凝聚来提高表面电荷密度而稳定;「ＺＣ     

表面活性单体存在下的MMA/BA乳液共聚合(Ⅱ)聚合动力学及机理

研究了表面活性单体[磺化-十二醇-烯丙基甘油-丁二酸酯钠盐(ZC-L)]的用量对MMA/BA/ZC-L乳液聚合速率和粒径的影响,用CoulterLS230型激光粒径分析仪测定聚合过程中乳液的粒径和粒径分布变化,并与MMA/BA无皂乳液聚合及十二烷基苯磺酸钠存在下的MMA/BA乳液聚合作了比较.[ZC-L]CMC时,成核机理包括均相成核和胶束成核机理,生成的粒子因吸收体系中的表面活性单体而稳定存在.