Influence of ingredients in water-based polyurethane–acrylic hybrid latexes on latex properties

Polyurethane–acrylic (PU–AC) hybrid latexes were prepared. Main monomers for PU preparation were isophorone diisocyanate, DMPA (dimethylol propanic acid) and polypropylene oxides (PPO) of different molecular weights. Acrylic monomers included butyl acrylate, methyl methacrylate and a crosslinker, trihydroxymethyl propane triacrylates (TMPTA). Several important ingredients in PU–AC latex preparation, such as surfactants, initiator, DMPA and PU/AC ratio, etc., were varied, and their effects on latex properties studied. Compared with surfactant free latexes, a sharp increase in particle size was observed in latexes done with 0.1% of surfactant regardless of the nature of the surfactants used (anionic, nonionic and anionic with long chain of amphiphilic alkylphenyl polyethoxylate). Further increase in surfactant content, however, led to latexes with smaller particle size and narrower particle size distribution when compared between latexes prepared using a same surfactant. When amount of the oil soluble initiator, azobisisobutyronitrile, was increased, AC monomers conversion was increased. It is interesting to observe that PPO with long propylene oxides brought about larger particle size combined with broader size distribution and less charge on particle surface; whereas lower DMPA levels led to latexes also of larger size combined with broader size distribution but more charges on particle surface. AC monomer crosslinker, TMPTA, contributed to reduce particle size, narrower size distribution and lower particle surface charges. By increasing AC amount in PU–AC latex, latex particle size significantly increased accompanied by a remarkable increase in particle surface charges. Mechanisms of particle formation and of DMPA stabilization were discussed in order to understand the experimental results.     

Synthesis and properties of copolymer microemulsions of siloxane and acrylate with a high solid content

Copolymer microemulsions of methyl methacrylate, butyl acrylate, and vinyltriisopropoxysilane with high monomer/surfactant ratios were prepared through a seeded semicontinuous polymerization in the presence of a redox initiator, ammonium persulfate/sodium hydrosulfate. The mean diameter of the particles decreased with an increase in the amount of the surfactant, the monomer concentration, and the vinyltriisopropoxysilane/monomer ratio, but it increased with an increase in the concentration of the initiator. When the initiator concentration was 0.23% (ammonium persulfate/sodium hydrosulfate = 1.5 : 1), the concentration of the composite surfactant was 0.9 wt %, and the reaction temperature was 50°C; the solid content of the microemulsion could be up to 43% with a small particle size (mean diameter) of 39.8 nm. The chemical, freeze–thaw, and mechanical stability of the latexes was tested as well as the thermal stability of the films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 851–857, 2007     

用阴离子Gemini 9 B-6-9 B乳化剂合成苯乙烯-丙烯酸丁酯共聚物纳米乳液

以壬基酚、1,6-二溴己烷、氯磺酸为主要原料合成的阴离子Gemini磺酸盐表面活性剂9 B-6-9 B为乳化剂,苯乙烯(St)、丙烯酸丁酯(BA)为单体,合成了乳胶粒径小于100 nm且分布均匀的苯乙烯-丙烯酸丁酯共聚物纳米乳液,考察了聚合温度、乳化剂用量、引发剂用量、单体配比、单体含量对乳液的影响,探讨了乳胶粒子成核机理。结果表明,随着温度的升高,乳胶粒子的平均粒径减小,转化率与凝胶率增大;随着乳化剂或引发剂用量的增加,乳胶粒子的平均粒径和凝胶率减小,转化率增大;随着软单体比例的增加,乳胶粒子的平均粒径与转化率增大,粒径分布变宽,凝胶率减小;单体用量增大,乳胶粒子的平均粒径与凝胶率增大,转化率降低;乳胶粒子的粒径呈单峰分布,可能是按胶束成核机理形成的。     

Preparation and characterisation of styrene—methyl methacrylate and styrene–methacrylic acid copolymer latices

Series of styrene-methyl methacrylate and styrene-methacrylic acid copolymer latices have been prepared by emulsion polymerisation using polyoxyethylene nonyl phenyl ether as emulsifier and potassium persulphate as initiator. the effects of surfactant concentration and monomer composition on the ultimate particle size and conversion were investigated. The ultimate particle diameters decreased with increasing surfactant concentration, while the conversions were found to be almost independent of surfactant concentration. The ultimate particle diameters were notably decreased by increasing the content of methacrylic acid. Trace carboxyl groups were detected both in polystyrene latex and styrene-methyl methacrylate copolymer latices. The number of sulphate groups on the polystyrene latex surface was about five times that of carboxyl groups.     

Preparation and properties of polymer lattices polymerised without surfactants

Series of polystyrene and polymethyl methacrylate latex dispersions have been prepared in the absence of any surfactant using potassium persulphate as an initiator. The latex particles are stabilised by the electrical repulsion generated by the sulphate groups which are covalently linked to the polymer molecules and are not removed by dialysis. The effects of polymerisation temperature, monomer concentration and initiator concentration on the ultimate particle size and conversion were investigated for these two series of lattices. The modal diameters of these lattices were found to be in the range of 530 to 1550 nm for polystyrene lattices, and 140 to 270 nm for polymethyl methacrylate lattices. The surface charge densities were calculated from conductometric titration results for polymethyl methacrylate lattices and were found to increase almost linearly with increase of the concentration of potassium persulphate used.     

VAc/MA/AA三元无皂乳液共聚的研究

以过硫酸钾(KPS)为引发剂,对VAc/MA/AA三元无皂乳液共聚进行了研究。探讨了引发剂用量、功能单体用量(AA)对乳液稳定性、胶乳粒子粒径、粒径分布及胶乳粘度、粘接强度等性质的影响。结果表明: 引发剂用量小于单体总质量的0．7％时,随着KPS用量的增加,胶乳粒子粒径减小,粒径分布变窄;引发剂用量大于单体总质量的0．7％时,随着KPS用量的增加,胶乳粒径及分布都增大,KPS用量为单体总质量的6％时,单分散性好;共聚乳液的粒径随AA用量的增加而增加,粒径分布则随AA用量的增加而减小,乳液粘度随AA用量增大而降低,而粘接强度随AA用量增大而增加,耐水性下降。     

Statistical experimental strategies approach to emulsion copolymerization of styrene and n-butyl acrylate

A batch emulsion copolymerization for the preparation of styrene-n-butylacrylate (St/BA) copolymer latexes is investigated. A series of n-butylacrylate-styrene copolymer latexes were obtained by emulsion copolymerization in the presence of K₂S₂O₈ (KPS) as initiator and with/without emulsifier (sodium lauryl sulfate). The effect of such preparation conditions as initiator concentration, the St/BA ratio, reaction temperature, agitation rate, and emulsifier concentration on the polymerization rate, particle size of copolymer latex, and molecular weight distribution of the resulting copolymer (∼ 80% conversion), respectively, is systematically studied using fractional factorial design methodology. Fractional factorial analysis indicates that the effects of the St/BA ratio, reaction temperature, emulsifier concentration, as well as the two-factor interaction of temperature and emulsifier concentration, are the key variables influencing the polymerization rate. At ∼ 80% monomer conversion, statistical analysis clearly isolates emulsifier concentration as the dominant factor affecting average particle size of copolymer latex; results also indicate that the effects of the St/BA ratio, reaction temperature, and emulsifier concentration are major effects influencing the polydispersity of polymer molecular-weight distribution. For 7.30 g KPS/100 g monomer and 500 rpm agitation rate, the conditions for minimizing molecular-weight distribution (∼ 80% conversion) occur for a reaction temperature, St/BA ratio, and surfactant concentration of 70°C, ∼ 3.59/1, and ∼ 2.08 g/100 g monomer, respectively, generating a minimum molecular-weight polydispersity of ∼ 3.0. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 551–563, 1998     

PVAc Microspheres via Semicontinuous Emulsion Polymerization: Synthesis,Characterization, Kinetic,and Surface Morphology Studies

Poly (vinyl acetate) (PVAc) latexes are economically important products with many desirable features. They are used as adhesives for porous materials in various processing stages of industries. Synthesis parameters have an important role on the physico-chemical properties of PVAc latexes such as: viscosity, average molecular weight, degree of polymerization, and surface morphology. In this work, PVAc was prepared via semicontinous emulsion polymerization (delayed monomer and initiator addition process) in the presence of ammonium persulfate (APS) as conventional anionic initiator, poly (vinyl alcohol) (PVA) as stabilizer, and sodium lauryl sulfate (SLS) as anionic emulsifier. The surface morphology of PVAc microspheres was, examined using a scanning electron microscope (SEM) and atomic force microscope (AFM). It is evident from the SEM photographs that all the particles became microspheres and are uniform in shape. The use of AFM for imaging of polyvinyl acetate confirms a typical sphere polymer. The effect of changes in the different parameters such as concentration of emulsifier, initiator concentration, and presence or absence of buffer on the vinyl acetate (VAc) conversion, the steady state polymerization rate, the viscosity-average molecular weight, and the final latex viscosity of synthesized PVAc were investigated. The effects of anionic emulsifier on the synthesized PVAc are also compared with those obtained by the nonionic emulsifier. The comparison indicated that the VAc monomer conversion and the final latex viscosity of the anionic system were higher than for the nonionic system but the viscosity-average polymer molecular weight of the anionic system was lower than that of the nonionic system. The adhesive strength of the synthesized PVAc latex was examined and the load and deflection data were reported.     

Emulsifier-free emulsion copolymerization of styrene with two different amino-containing monomers: II. Surface and colloidal characterization

The colloidal and surface properties of copolymer latex particles prepared by batch emulsifier-free emulsion polymerization of styrene with two different amino-containing monomers (Amino Ethyl Methacrylate Hydrochloride (AEMH) and Vinyl Benzyl Amine Hydrochloride (VBAH)), and 2,2′-azobis(2-amidinopropane) dihydrochloride (V50) as initiator were investigated. The final particle size was found to decrease with increasing the functional monomer concentration. Different titration methods were used to quantify the surface amino (brought by the monomer) and amidino groups (originated from the initiator) on the latex particles. The same behavior was observed on both type of latexes: increasing the functional monomer concentration caused the surface amino groups density to increase from 0 to a plateau value at 8.2 μC/cm², whereas the surface amidino groups density decreased from 18.5 to 2 μC/cm². These results were confirmed by electrophoretic measurements and they corroborated those obtained in a previous kinetic study (Part 1) concerning the role of functional monomers as transfer agents. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2331–2342, 1997     

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.     

高固含量有机硅改性丙烯酸酯微胶乳的合成及性能

用自制的由阴离子乳化剂十二烷基硫酸钠(SDS)、非离子乳化剂辛基酚聚氧乙烯醚(OP-10)、反应型乳化剂WH-100以及非离子表面润湿剂所组成的混合乳化剂体系,通过半连续单体滴加法合成了平均粒径为59·8nm、粒径分布窄、总固物质量分数达40%的有机硅改性丙烯酸酯微胶乳,并对微胶乳及胶膜的性能进行了研究。结果表明,与间歇预乳化法制备的乳液相比,有机硅改性丙烯酸酯微胶乳的钙离子稳定性较差,其胶膜的吸水率较小,凝胶含量相当;随着乙烯基三乙氧基硅烷(A151)用量的增加,对转化率的影响不明显,微胶乳的钙离子稳定性、胶膜的吸水率下降,乳胶粒子的粒径变大,A151的质量分数宜为4%;随着功能单体甲基丙烯酸-2-羟乙酯(HEMA)用量的增加,微胶乳的钙离子稳定性先提高后降低,而胶膜的吸水率先降低后增大,HEMA的质量分数不宜超过3%。     

Factorial experimental design approach in semicontinuous emulsion polymerization of methyl methacrylate to study the effect of process variables

This article describes the effect of various process variables in the semicontinuous emulsion polymerization of methyl methacrylate. A series of poly(methyl methacrylate) (PMMA) emulsions were prepared using ammonium persulphate as initiator in absence and presence of Dowfax 2AI as surfactant. The effect of process variables such as initiator concentration, monomer concentration (solid content), surfactant concentration, reaction temperature, monomer feeding time, and holding time were systematically studied on monomer conversion, particle size, gel content, and molecular weight using a two‐level fractional factorial experimental method. Analysis of fractional factorial design revealed that surfactant concentration, monomer concentration, initiator concentration, and monomer feeding time affect all the properties. However, the surfactant concentration and the interaction effect of initiator and monomer feeding time are the key variables influencing the properties of PMMA latex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of model carboxylated latexes for studies of film formation from latex blends

Poly(n‐butyl methacylate‐co‐n‐butyl acylate) [P(BMA/BA)] soft latexes (carboxylated and noncarboxylated) were synthesized using a semicontinuous emulsion polymerization process that was designed on the basis of a theoretical calculation to determine the suitable surfactant [i.e., sodium dodecyl sulfate (SDS)], monomer, and water feed rates to maintain a constant particle number throughout the polymerization (guaranteeing monodispersity in the particle size), to obtain a homogeneous copolymer composition, and to independently control the particle size and carboxyl group concentration. The experimental results support the theoretical calculation. The surface coverage of the carboxyl groups present on the soft latex particles ranges from 7.6 to 21.9% for a series of latexes with particle sizes around 120 nm. In another series of latexes, the particle size was varied over a range from 120 to 450 nm. Monodisperse carboxylated polystyrene hard latexes were synthesized by shot growth (batch) and semicontinuous processes. The shot growth method is somewhat inflexible in providing more choices in surfactant, particle size, and surface carboxyl coverage. A semicontinuous process designed using a similar method used for the synthesis of P(BMA/BA) latexes successfully eliminated the drawbacks of the shot growth process. In this way, the changes in the surface carboxyl coverage (varies from 0 to 77.2%) was independent of the particle size, which was precisely controlled by the amount of styrene fed under suitable styrene and SDS feed rates. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 644–659, 2000     

A study on the synthesis of acrylic composite particles and investigation of their characterization

Core-shell latexes were synthesized by sequential emulsion polymerization of methyl methacrylate (MMA), styrene (St), and ethyl acrylate (EA) in the presence of anionic surfactant, and the characteristics of these latexes were evaluated. The core latex had to be synthesized carefully to avoid the formation of secondary particles. The sequential polymerization method adopted for this synthesis took advantage of stabilizing particles grown during shell polymerization. In core-shell latex polymerization, to suppress the generation of new particles and to minimize the gelation during the shell polymerization, the amount of surfactant (Sodium dodecyl benzene sulfonate: SDBS) should be reduced to the minimum, 0.01 wt% and 0.02 wt% of SDBS to amount of monomer, respectively, when the Polymethyl methacrylate (PMMA) and Polystyrene (PSt) core latexes are prepared. In addition, the monomer pre-emulsion method is better than monomer-add method. The core-shell structure for composite latex synthesized was demonstrated by Particle Size Analysis (PSA), Differential Scanning Calorimeter (DSC), Transmission Electron Microscope (TEM), formability of film, and hydrolysis under NaOH solution.     

Entry in emulsion polymerization using a mixture of sodium polystyrene sulfonate and sodium dodecyl sulfate as the surfactant

A mixture of sodium polystyrene sulfonate (NaPSS) and anionic surfactant, sodium dodecyl sulfate (SDS), was used as the emulsifier in the emulsion polymerization of styrene at 60 °C. The latexes prepared were stable, bearing the better resistance to the addition of electrolyte, and have the larger values in particle size and the higher polymerization rates than those counterparts prepared using SDS only. The NaPSS was prepared by a series of process: a concentrated cyclohexane solution of an anionically polymerized polystyrene (PS) was sulfonated with sulfuric acid at 80 °C, and then neutralized and purified through dialysis. The data of average polymer number per particle (n_p) were found useful in investigating the surfactant content effect on the entry of radicals into particles, where the latex particle size plays an important role.     

Preparation and characterization of waterborne epoxy latexes and epoxy/(silica sol) composites

A series of waterborne epoxy latexes was synthesized, and epoxy/(silica sol) composite latexes were prepared. The effects of functional monomer methacrylic acid (MAA) and silica sol on the latex particle size, morphology, and stability were investigated. With increasing amounts of MAA, the conversion rate increased, the particle size reduced, and the viscosity of the epoxy latexes increased. The epoxy latexes had storage stability and could be stored at room temperature for more than 6 months with a solid content variation of less than 1%. For the (silica sol)‐modified waterborne epoxy latexes, the effects of preparation techniques and silica sol content on the latexes and latex films were investigated. When the silica sol content increased, the particle size of the composite latexes decreased. The morphology investigation showed that when the silica sol content increased, the uneven surface level of the latex films was increased. The increase of elemental silica on the surface was in accord with the improvement of the water resistance of the composite latex films. The heat resistance of these films was improved as well, and their overall performance was better than that of the epoxy latex films. J. VINYL ADDIT. TECHNOL., 20:57–64, 2014. © 2014 Society of Plastics Engineers     

Associative polymer/latex dispersion phase diagrams II: HASE thickeners

The colloidal interactions of HASE associative polymers and latexes in the presence of surfactant are complicated and subject to a number of variables. Both bridging and depletion flocculation can occur, in addition to good particle dispersion. Dispersion phase diagrams have been developed to help visualize these interactions. The various dispersion states can have a significant effect on coating formulations and film properties. Examples of dispersion phase diagrams are presented for a model HASE anionic associative thickener and various model latexes in the presence of sodium dodecyl-sulfate and nonionic surfactants. The major variables affecting dispersion behavior are associative polymer concentration, latex particle size, latex surface hydrophobicity, electrolyte concentration, and surfactant concentration. The dispersion phase behavior of the HASE systems is compared to that of HEUR thickened systems reported previously. A significant difference is that much less bridging flocculation is observed in the HASE systems. In addition, nonionic surfactants induced depletion flocculation in the HASE systems but not in the HEUR systems.     

Synthesis and properties of branched organosilicon-acrylate copolymer latexes

Summary Stable organosilicon-acrylate copolymer latexes with high silicon content were prepared by seeded semibatch emulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA) with a novel branched organosilicon monomer 3-methacryloxypropyl tris(trimethylsiloxy) silane (MPTS). Monomer conversion, evolution of the particle size and its distribution were monitored by dynamic light scattering. The effects of MPTS on the polymerization kinetics, the nucleation mechanism and properties of latex were investigated. The results indicated that, in addition to micellar nucleation, a coagulative nucleation step was also observed as a result of the addition of the organosilicon monomer, accordingly, the particle number of the silicon-acrylate latexes increased, the average particle diameter decreased and the polymerization rate accordingly increased compared to those of the acrylate latexes without organosilicon monomer. Moreover, the particle size distribution presented bimodal curves, which indicated that there were large particles formed at an early stage. However, the particle size distribution curves became monomodal at the later stage, and the final latex shows a narrow particle size distribution. It was found that the properties of latex and latex film were obviously influenced by MPTS content. With increasing MPTS content, latex film glass transition temperature and water absorption ratio decreased, the degradation temperature and water contact angle were increased. Hence, the resulting latex films containing MPTS showed lower glass transition temperature and excellent water-resistance, which probably due to the incorporation of the bulky branched hydrophobic group of MPTS into the copolymer chains.     

稳定的阳离子型聚合物纳米粒子胶乳的研制

以甲基丙烯酸甲酯 ( MMA)和丙烯酸乙酯 ( EA)为主单体 ,甲基丙烯酰氧乙基三甲基氯化铵( DMC)为功能单体 ,分别采用 4种阳离子乳化剂和阴离子引发剂过硫酸铵 ( A PS)进行自由基乳液共聚合。探讨了乳化剂种类和用量、聚合温度及加料方式对乳胶粒大小、胶乳稳定性和胶膜耐水性的影响。研究发现 ,当采用十六烷基三甲基氯化铵 ( 16 31)作乳化剂 ,用量为 1.75%～ 2 .0 % ,聚合温度为 70℃ ,采用种子半连续法可以成功研制出粒径为 57.5nm、稳定的耐水性较好的阳离子型聚合物纳米粒子胶乳     

Semi-continuous emulsion copolymerization of butyl methacrylate with polymerizable anionic surfactants

Two polymerizable anionic surfactants sodium 4-(ω-acryloyloxyalkyl)oxy benzene sulfonate (SABS-n, n=8 or 10) have been successfully used in the semi-continuous emulsion copolymerization with butyl methacrylate (BMA). After generating seeding particles in an emulsion consisting SABS-8 or SABS-10 and small amount of BMA using a redox initiator ammonium persulfate (APS)/tetramethylethylenediamine (TMEDA) at room temperature, most of BMA was added drop-wise to the polymerizing emulsion system during a period of 4-8 h. These emulsion copolymerizations produced nanosized latexes with high polymer/surfactant weight ratios up to about 12/1 and nearly monodisperse particles ranging from 18 to 33 nm in diameter. X-ray photoelectron spectroscopy results showed that SABS-n was significantly enriched on the surface of latex particles. The effects of concentrations of SABS-n, BMA, and APS/TMEDA and the latex characteristics during the continuous addition of monomer were studied. A possible polymerization mechanism was proposed.