Emulsion polymerization of vinyl acetate initiated by intermittent γ radiation

The reaction kinetics of emulsion polymerization of vinyl acetate (VAc) monomer have been studied by using intermittent γ radiation. The purpose of this technique is to take advantage of the poly merization reaction which still continues after the radiation production has been stopped, as expected by the Smith–Ewart rate theory. Tween 20 (polyoxyethylene sorbitan monolaurate), was used as the emulsifier. The polymer conversion was determined by using the dilatometric method. The polymerization rate R_p decreased with increase in emulsifier content. The Smith–Ewart rate theory cannot explain the experimental evidence satisfactorily. The average polymerization rate R_p between 20% and 80% conversion is a function of irradiation dose rate and can be written where a₁ and a₂ is a constant in which the value depends on the emulsifier content in the emulsion and I is the irradiation dose rate.     

Polyurethane‐acrylic hybrid emulsions with high acrylic/polyurethane ratios: Synthesis,characterization, and properties

Allyl polyoxyethylene ether (APEE) was used as coupling agent between polyurethane (PU) and acrylic polymer (AC) to synthesize stable waterborne polyurethane‐acrylic (PU‐AC) hybrid emulsions with high AC/PU weight ratio ranged from 45/55 to 70/30. The effect of the AC/PU weight ratio and the acrylate type including methyl methacrylate (MMA), butyl acrylate (BA) and mixture of them on the properties of the synthesized emulsions and resultant films were investigated. The research results showed that the colloidal particle of the emulsions behaved core‐shell structure, and the copolymers were not crosslinked. An increase in the AC/PU weight ratio led to an increase in the average particles size and the particle size distribution, but decrease in the viscosity of the emulsions. Meanwhile, the molecular weight distribution of the copolymers became wide, and the tensile stress, shore A hardness, storage modulus, glass transfer temperature, water resistance, and water contact angle of the resultant films increased, except that the films of PU‐BA were too soft to determine their mechanical properties. MMA and BA can provide the PU‐AC hybrid emulsions with very different properties, and which can be adjusted according to the special application. It was suggested that APEE can not only built up chemical bonds between PU and AC, but also increase the self‐emulsifying ability in the emulsion polymerization due to its hydrophilic ethylene oxide and carboxylic groups, resulting in that PU‐AC hybrid emulsions with high AC/PU ratio can be obtained by this method. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44488.     

Desorption of free radicals in semibatch emulsion polymerization of methyl acrylate

Desorption of free radicals from particles can cause an emulsion polymerization system to deviate from Smith–Ewart case II kinetics. A mechanistic model has been developed to predict the effect of desorption of radicals from particles on the kinetics of semibatch emulsion polymerization of methyl acrylate under the monomer-starved condition. Experimental data available in the literature are used to assess the proposed kinetic model. The model predicts the experimental data reasonably well for a wide range of monomer feed rates. The rate of polymerization increases with an increase in the rate of monomer addition. The kinetic data are also useful in evaluating the desorption rate constant (K′_d) for methyl acrylate. The best fitted value of K′_d at 50°C is 4 × 10^-12 cm²/s, which is in good agreement with the theoretical values predicted by desorption theory. © 1995 John Wiley & Sons, Inc.     

反应型乳化剂对醋-丙微皂乳液聚合及性能的影响

以醋酸乙烯酯,丙烯酸丁酯和甲基丙烯酸甲酯为原料,采用反应型乳化剂SVS与传统乳化剂（SDS,OP-10）复配,制备了具有核壳结构的醋-丙微皂乳液,讨论了软硬单体的选择,乳化剂选择及用量对乳液及涂膜性能的影响,并采用DSC,TEM等对共聚物的结构和乳液的性能进行表征。结果表明,通过半连续核壳乳液聚合方式,采用合适的反应型乳化剂复配体系,可用于制备综合性能优异,乳胶粒子粒径在80-100nm的醋-丙微皂乳液。     

Synthesis of a latex with bimodal particle size distribution for coating applications using acrylic monomers

Multipart emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in this work. The target was to achieve stability during the polymerization and to determine the proper hydrophilic–lipophilic balance (HLB) value for the stable system, using different types of non-ionic emulsifiers, sodium lauryl sulphate and their combinations. After determination of proper value of HLB (36.2), the best emulsifier combination on the basis of minimization of coagulum level was determined. This combination was 20 wt.% of KENON30 to SLS. The effect of monomer feed composition on the dry latex film properties was investigated to approach a monomer feed composition dealt with a proper T_g. The prepared latex showed a bimodal particle size distribution, due to the proper feeding policy in semibatch emulsion copolymerization process. The monomer feed composition of 45 wt.% MMA and 55 wt.% BA with a proper T_g was selected for the final improvement of coating properties such as UV resistance and adhesion. Adding acrylic acid (AA) and N-methylol acrylamide (NMA) to the reaction mixture improved the UV resistance and adhesion property of dry latex film. The flow and leveling, gloss, adhesion, UV resistance and water resistance of the produced bimodal latex showed good quality in comparison with the similar commercial resins used in coating applications.     

Semibatch emulsion polymerization of butyl acrylate. I. Effect of monomer distribution

The effects of initial monomer charge on the particle formation and on the rate of polymerization were investigated for semibatch emulsion polymerization of butyl acrylate using sodium lauryl sulfate (SLS) as a surfactant and potassium persulfate (KPS) as an initiator. For the semibatch process with monomer (M) feed, it was found that by varying the monomer distribution ratio between the initial reactor charge and the feed it is possible to alter the contribution of monomer‐flooded and monomer‐starved nucleation mechanisms to the whole nucleation process. The number of particles increases as the initial monomer charge decreases, if the monomer concentration is below a critical value for any fixed system. The increase in number of particles is associated with a broad particle‐size distribution which might depict an emerging second peak on the particle‐size distribution curve. For low emulsifier concentration systems, a larger number of particles was obtained for a lower amount of monomer charge. Particle coagulation and emulsifier adsorption on the monomer droplets were counted as the main reasons for such behavior. For a semibatch process with monomer emulsion (ME) feed, the larger number of particles was formed at a lower initial monomer charge, similar to an M‐add semibatch process. However, the application of monomer charge to an ME‐add process was found to increase the possibility of secondary nucleation and led to the occurrence of a bimodal particle‐size distribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3094–3110, 1999     

Study of different types of monomer emulsion feedings to semibatch emulsion polymerization reactors

Semibatch emulsion polymerization processes with a monomer emulsion feed are of great importance in both academia and industry. Monomer emulsion feeds can be applied to semibatch reactors using either a stream of an emulsified monomer or two streams of a neat monomer feed and an aqueous solution of an emulsifier. The effect of the feeding policy on the rate of polymerization and on the secondary particle formation was studied for a seeded semibatch emulsion polymerization of styrene. When a single-stream monomer emulsion feed is applied to a semibatch process, the monomer-swollen micelles formed in the feed might become the locus of initiation upon entering the reaction vessel. Under the conditions of this study, the application of monomer emulsion feed in either one stream or two streams did not result in secondary particle formation. The incoming monomer-swollen micelles were disintegrated to supply emulsifier molecules for the stability of growing particles, before they can capture radicals and become polymer particles. The rate of polymerization was found to be independent of the way that the monomer emulsion feed is added. In the absence of nitrogen, the rate of polymerization decreased more appreciably for the monomer emulsion feed, due to the oxygen dissolved in the emulsified monomer. The number of particles, however, was not affected by the purging policy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2472–2477, 2001     

核壳型纳米SiO2/含氟聚丙烯酸酯复合乳液的合成与表征

采用原位乳液聚合法,在可聚合阴离子乳化剂/非离子乳化剂复配体系下,以γ-甲基丙烯酰氧丙基三甲氧基硅烷(KH-570)改性的纳米SiO2、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、丙烯酸(AA)等为核相组成,以MMA、BA及甲基丙烯酸十二氟庚酯(DFMA)为壳相单体,合成纳米SiO2/含氟聚丙烯酸酯复合乳液.考察了纳...     

BA‐MMA‐POMA copolymer latexes prepared by using HMPS polymerizable emulsifier

BA‐MMA‐POMA copolymer latex was successfully prepared by soap‐free emulsion polymerization of 2‐(perfluoro‐(1,1‐bisisopropyl)‐2‐propenyl)oxyethyl methacrylate(POMA) with butyl acrylate(BA), methyl methacrylate (MMA) initiated by K₂S₂O₈ in the water. POMA was synthesized from the intermediate perfluoro nonene and 2‐hydroxyethyl methacrylate as the staring reactants. The structure of BA‐MMA‐POMA copolymer latex was investigated by Fourier transform infrared (FTIR). The characteristics of the film such as hydrophobicity and glass transition temperature were characterized with the contact angle and differential scanning calorimetry respectively. The influences of the amount of the fluorinated monomer and the initiator on the soap‐free emulsion polymerization and performance of the latex were studied. In addition, comparison with the latex prepared by the conventional emulsifier SDBS is investigated. Results show that the hydrophobicity and glass transition temperature (T_g) of the latex are increased when the fluorinated monomer is introduced to copolymerize with other monomers. The hydrophobicity can be improved further with heating. Compared with the latices prepared by using SDBS emulsifier, the latices prepared by using HMPS emulsifier have larger particle size, higher surface tension. However, the difference of their T_g is extremely minute. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphologies and dynamic mechanical properties of core‐shell emulsifier‐free latexes and their copolymers for P(BA/MMA)/P(MMA/BA) and P(BA/MMA)/PSt systems in the presence of AHPS

Different poly(methyl methacrylate/n‐butyl acrylate)/poly(n‐butyl acrylate/methyl methacrylate) [P(BA/MMA)/P(MMA/BA)] and poly(n‐butyl acrylate/methyl methacrylate)/polystyrene [P(BA/MMA)/PSt] core‐shell structured latexes were prepared by emulsifier‐free emulsion polymerization in the presence of hydrophilic monomer 3‐allyloxy‐2‐hydroxyl‐propanesulfonic salt (AHPS). The particle morphologies of the final latexes and dynamic mechanical properties of the copolymers from final latexes were investigated in detail. With the addition of AHPS, a latex of stable and high‐solid content (60 wt %) was prepared. The diameters of the latex particles are ～0.26 μm for the P(BA/MMA)/P(MMA/BA) system and 0.22–0.24 μm for the P(BA/MMA)/PSt system. All copolymers from the final latexes are two‐phase structure polymers, shown as two glass transition temperatures (T_gs) on dynamic mechanical analysis spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3078–3084, 2002     

含3nm硅溶胶的苯丙杂化乳液的制备与性能研究

在单一乳化剂存在下 ,用原位分散聚合方法制备了含 3 nm硅溶胶的苯丙杂化乳液。通过 FTIR、粒径分析、ζ电位和流变性能测试 ,表征了杂化乳液中的杂化效应、微粒形态及乳液稳定性 ,并与分别由 3 nm和 1 0 nm硅溶胶与苯丙乳液直接共混形成的杂化乳液进行了比较。与直接共混的杂化乳液成膜后的力学性能相比 ,由原位分散聚合形成的 3 nm硅溶胶杂化乳液成膜后 ,显示出较高的拉伸强度、拉伸模量和断裂伸长率。     

核壳型丙烯酸酯乳液的制备与性能研究

采用甲基丙烯酸甲酯／丙烯酸丁酯作复合单体,丙烯酸为功能单体,通过预乳化半连续种子乳液聚合工艺合成了核壳型丙烯酸酯乳液,讨论了反应温度、乳化剂用量、核壳单体质量比以及丙烯酸加入量对乳液性能以及漆膜力学性能的影响,并用TEM对乳胶粒子进行了表征。结果表明：采用预乳化半连续滴加法,当复合乳化剂SDS与OP-10质量比为2：1且总用量为4％,核、壳层中甲基丙烯酸甲酯与丙烯酸丁酯的质量比分别为3：7和4：1,核壳总单体质量比为1：1,丙烯酸质量分数为4％,核层和壳层反应温度分别为70℃和80％时,可以合成黏度适中、乳胶粒粒径分布均匀、稳定性好和漆膜力学性能优良的核壳型丙烯酸酯乳液。     

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     

Semibatch emulsion polymerization of butyl acrylate. II. Effects of emulsifier distribution

The effects of emulsifier distribution ratio between the initial charge and the feed on particle formation and kinetics of butyl acrylate emulsion polymerization, using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator, were investigated. The number of particles increased with initial emulsifier concentration in the reactor charge. It was shown that traditional ranking, in terms of number of particles produced, of semibatch emulsion polymerization with monomer emulsion feed is not always justified and a semibatch emulsion polymerization can produce far more particles than a conventional batch emulsion polymerization. The number of polymer particles was found to be practically independent of the emulsifier distribution ratio between the charge and the feed for a high overall emulsifier concentration, while for a low overall emulsifier concentration, the number of particles increased with initial loading of the emulsifier. The polydispersity index (PDI) of the final latexes showed a minimum with emulsifier distribution. A bimodal particle size distribution, and a latex with a large PDI, was obtained when there was no emulsifier in the charge. As the initial emulsifier charge increased, a unimodal PSD with a smaller PDI was obtained. With higher proportions of emulsifier in the initial charge, the PDI rose again due to particle nucleation at monomer‐starved conditions, and a skewed unimodal PSD was obtained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 582–597, 2001     

Polymer–leather composites. II. Kinetics of the deposition of selected acrylate monomers by polymerization into chrome-tanned cattlehide

Limited kinetic information on a convenient process for depositing polymer in 5-oz cattlehide is presented in this article. The work includes a systematic study of the total polymerization rate and of the derived rates of deposition into the fibrous matrix, of bound polymer formation, and of polymer production in the external aqueous phase (the float) for three acrylic monomers. The monomers used, with a persulfate–bisulfite redox initiating system at 27°C, were methyl methacrylate (MMA), n-butyl acrylate (BA) and a fixed mixture of n-butyl acrylate and methyl methacrylate (BA + MMA). The effects of the reaction variables on rate, as measured by their intensity exponents, were not in agreement with a rate expression proposed to describe grafting in homogeneous polymerization, nor were they wholly compatible with classical and modified Smith–Ewart theories for heterogeneous emulsion polymerization. The experimental behavior, however, was in harmony with self-nucleation in the aqueous phase. Exponential orders of dependence were initiator > 0.5 (MMA, 0.72; BA + MMA, 0.66); monomer, zero; surfactant, ～0.5. The approximately 0.6 order dependence (MMA, 0.9) on leather amount was shown to be largely apparent and to decline as total polymerization proceeded. Thus a dominant grafting reaction was not supported. In support of this conclusion, simple impregnation of the matrix with preformed emulsion polymer yielded the same amount of bound polymer as that formed in situ. It was concluded that monomer is initiated largely from active centers formed initially near fibers or fibrils to form embryo polymer particles, which join penetrating swollen polymer particles and become unstable. These nucleate a polymer front, containing occluded radicals, which grows by diffusion regulated transport of monomer to complete deposition.     

Semibatch anionic ring‐opening polymerization of octamethylcyclotetrasiloxane in emulsions: effect of the amount of seed polymer particles

Semibatch anionic ring‐opening polymerization of octamethylcyclotetrasiloxane with the use of seed polymer particles in emulsions was studied. The concentration of the emulsifier was set above the critical micelle concentration. We investigated the effect of the amount of seed polymer particles on the chemical kinetics and the average particle size and distribution. During monomer starving conditions the polymerization rate strongly depended on the monomer feed rate and not on the amount of seed particles. Throughout the entire monomer feed period the average particle size increased. This increase depended on the number and the size of seed particles. In emulsions with higher particle sizes higher equilibrium conversions were obtained. In our opinion, a greater extent of backbiting reactions is responsible for lower equilibrium conversions during and at the end of the process. The seeded semibatch process seems a reasonable choice for designing emulsion products with high monomer conversion and desired particle size. © 2012 Society of Chemical Industry     

Kinetics and latex particles analysis on styrene emulsion polymerization induced by <Superscript>60</Superscript>Co γ rays in presence of anionic polymerizable emulsifier

⁶⁰Co γ rays induced styrene emulsion polymerizations were carried out with sodium undec-10-enoate (UDNa) as emulsifier at room temperature and the different kinetics was discussed. The influence of absorbed dose rate, monomer concentration and emulsifier concentration on kinetics and latex particles was studied. The polymerization kinetics relation was found as R _P ∝ D ^0.37 · M ^0.75 · E ^0.70 (R _P , maximum polymerization rate; D, absorbed dose rate; M, monomer concentration; E, emulsifier concentration). The particles’ diameter increases and particle size distribution (PSD) becomes narrower with the decrease of absorbed dose rate and increase of monomer content. The effect of UDNa content on particles’ diameter and particle size distribution is the same as that of emulsifier in conventional emulsion system. This type of emulsion polymerization can easily form monodisperse particles.     

Comparison of properties of acrylic–polyurethane hybrid emulsions prepared by batch and semibatch processes with monomer emulsion feed

Aqueous acrylic–polyurethane hybrid emulsions were prepared by batch and semibatch polymerization of acrylic monomer mixtures (butyl acrylate, methyl methacrylate and acrylic acid) in the presence of polyurethane dispersion. The acrylic component was introduced in the monomer emulsion feed. The weight ratio between acrylic and polyurethane components was varied to obtain different emulsion properties, microphase structure and mechanical film properties. Scanning electron microscopy, average particle size and molecular weight measurements were performed to characterize the latex systems. Mechanical properties were examined by measuring Koenig hardnesses of dried films. The average particle size increased with the acrylic/polyurethane ratio. Particles of larger than average size and, to some extent, higher than average molecular weights by batch process were formed. Koenig hardnesses decreased with increasing acrylic/polyurethane ratio. Properties of emulsions synthesized by semibatch processes were compared with the results reported for a different polyurethane dispersion. Copyright © 2003 Society of Chemical Industry     

Influence of compositions and polymerization processes on morphologies,molar mass distributions,and phase structures of n‐Butyl acrylate–methyl methacrylate copolymers

The target of the research is to examine influence of a polymerization process and monomer ratio on structures and compositions of phases in an emulsion copolymerization of n‐butyl acrylate (BA) and methyl methacrylate (MMA). Emulsion copolymerizations are performed using three different BA/MMA weight ratios (60%/40%, 50%/50%, and 40%/60%) and two different processes, statistical batch and seeded emulsion polymerizations. Phase structures, monomer compositions, and morphological stabilities of copolymers are investigated by differential scanning calorimetry, ¹H‐NMR, and scanning electron microscopy. Gel permeation chromatography is used to follow the changes in the molar mass distribution during syntheses. The gel content and backbiting level of end products are measured by extraction and ¹³C‐NMR, respectively. Copolymerizations give products with a bimodal molar mass distribution and three or two separate phases having different BA/MMA compositions. The morphological stability of particles decreases with the increasing BA fraction in the feed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41467.     

Synthesis of CaCO3–P(MMA–BA) nanocomposite and its application in water based alkyd emulsion coating

As part of broader effort to synthesize a new class of water-based composite, hybrid emulsion polymerization was carried out with acrylic monomers [methyl methacrylate (MMA), n-butyl acrylate (BA)]. Nanocomposite of P(MMA–BA)/nano CaCO₃ was synthesized by in situ emulsion polymerization. Water-based alkyd coating with various proportions nano CaCO₃, P(MMA–BA) and its nanocomposite was formulated. Extent of polymerization with and without nano CaCO₃ was measured using gravimetric method. Thermal properties of neat polymer, nanocomposite and coating films were evaluated by TGA and DSC, DTA analysis. Uniform dispersion of nano CaCO₃ in polymer matrix was ensured from SEM/TEM images. Incorporation of nanoparticles to hybrid polymer and nanocomposite to alkyd emulsion showed significant enhancement in mechanical and thermal properties. Dual role of nanocomposite in coating; as a partial binder and a filler to improve property profile of neat coating has been reported.