PREPARATION AND STUDY ON SILICONE ACRYLATE MICRO-EMULSION OF MULTIPOLYMER

A silicone acr3,1ate micro-emulsion of multipolymer was prepared by seed emulsion polymeri.Tation. The effects of polymerization process, emulsifier rate and amount, initiator rate and amounl, polymerization temperalure, functional monomers, titration time on performances of emulsion have been discussed in detail.     

碱溶性无规共聚物表面活性剂的合成及在乳液聚合中的应用研究

合成了碱溶性无规共聚物聚 (甲基丙烯酸甲酯 丙烯酸乙酯 甲基丙烯酸 ) (MMA EA MAA) ,并对其结构、表面活性进行了表征研究 .以合成的P(MMA EA MAA)作高分子表面活性剂 ,进行甲基丙烯酸丁酯的乳液聚合 .研究了反应温度 ,引发剂浓度 ,表面活性剂浓度等因素对反应速率 (Rp)的影响 .结果表明 ,聚合速率随引发剂浓度 ,表面活性剂浓度的增加而增加 ;该体系的表观活化能为 85 19kJ·mol- 1 .用透射电镜 (TEM)表征了所制备的乳胶粒子形态 ,乳胶粒子呈较明显的核 壳结构 .     

Stability of Emulsion Polymerization of New Fluorinated Acrylate Emulsion and Its Characterization

The new fluorinated acrylate emulsion was synthesized by using the intermediate perfluorous nonene and 2-hydroxyethyl methacrylate as the staring reactants via semi-continuous seeded emulsion polymerization. The structures, glass transition temperature, thermal property and water repellency of the fluorinated acrylate emulsion were characterized with FTIR, differential scanning calorimetry, thermal analysis, and contact angle meter. Influences of many factors such as the theoretical solid content, the temperature of the emulsion polymerization on the stability of the emulsion polymerization, the added amount of emulsifiers and the added amount of the initiator were studied. Results show that the stability of the emulsion polymerization is fairly good when the theoretical solid content is below 30% and the reaction temperature is 80°C and the added amount of emulsifiers and the initiator are 6.0–8.0% and 2.0% respectively. In comparison with the acylate emulsion, the thermal stability of the fluorinated acrylate emulsion is decreased but the water repellency of the fluorinated acrylate emulsion is greatly increased.     

Emulsion polymerization of acrylonitrile. Part II. Mechanism of emulsion polymerization of acrylonitrile

The mechanism of emulsion polymerization of acrylonitrile has been studied by measuring by dilatometry and electron microscopy the adsorption of monomer into polymer particles and polymerization characteristics such as rate, degree of polymerization, the growth of the particle during polymerization, and the degree of dispersion. In the emulsion polymerization of acrylonitrile, new particles are formed during polymerization at a rate which is proportional to the rate of polymerization and the ratio of unreacted monomer. The total amount of monomer adsorbed on or in the polymer particles is rather small, but the concentration on or in the polymer particles is sufficiently high and proportional to the monomer concentration in aqueous phase. The polymerization proceeds concurrently on or in the polymer particles and in aqueous phase, but the three loci may be continuous rather than discrete. A reaction scheme is introduced here which shows the coexistence of polymerizations on or in the polymer particles and in the aqueous phase.     

Radiation-Induced Emulsion Copolymerization of Tetrafluorethylene with Propylene. The Behavior of the HF Formed

The radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out at room temperature in the presence of gaseous monomers. The formation of hydrofluoric acid in the course of polymerization was observed. The amount of HF formed increased linearly with the irradiation time at various dose rates in the early stage. The tendency was similar to that of time-polymer yield curves. The rate of HF formation was proportional to the first order of the dose rate. The amount of HF formed increased in the presence of oxygen and decreased remarkably above 1 wt% emulsifier, while the polymer yield decreased in the presence of oxygen and increased with the emulsifier concentration. A remarkable decrease in the amount of HF formed in higher emulsifier concentration is mainly attributable to chemical absorption or electrostatic capture of H⁺ ion on polymer particles produced. Hydrofluoric acid is mainly formed by reaction between primary products (e _aq ^? and H) from the radiolysis of water and organic fluoride (tetrafluoroethylene and emulsifier), and is little formed by reaction between primary products and copolymer produced. The G value of HF formation was in the order of emulsifier-water system > suspension polymerization > emulsion polymerization, while the polymer yield was in the order of emulsion polymerization > suspension polymerization.     

Preparation and characterization of pure polyacrylate polymer colloid through emulsion polymerization using a novel initiator

A series of acrylic polymer colloids were prepared via semi-continuous seeded emulsion polymerization of BA and MMA in water phase when OP-10 and AIBI is used to be emulsifier and initiator, respectively. FTIR spectrum identifies the formation of copolymers of P (MMA-co-BA). DSC confirms that the colloid is a kind of random copolymer and the consistency among the chain segment is fairly good. The emulsion polymerization conditions of preparing acrylic polymer colloid are optimized. Results show that the conversion rate is high and the coagulum is low and the particle size of the acrylic polymer colloids is small when the amount of AIBI is 0.75 g. The polymerization temperature is 70 °C, which is lower than the one that the emulsion polymerization is initiated with the persulfate.     

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.     

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     

On the main locus of radical formation in emulsion polymerization initiated by oil-soluble initiators

The effect of the monomer/water ratio on the rate of polymerization per polymer particle in both seeded emulsion polymerizations and miniemulsion polymerizations was used in an attempt to elucidate the main locus of radical formation in emulsion polymerization initiated by an oil-soluble initiator (AIBN). It was found that, for the rest of conditions constant, the polymerization rate per polymer particle increased when the monomer/water ratio increased, namely when the amount of initiator dissolved in the aqueous phase per polymer particle decreased. This is an evidence against a dominant aqueous phase formation of radicals. On the other hand, these results are consistent with a mechanism in which the radicals are mainly produced in the oil-phase with significant aqueous phase termination.     

On the rate of soapless emulsion polymerization of methyl methacrylate

The rate of soapless emulsion polymerization is studied experimentally and theoretically. The soapless emulsion polymerization of methyl methacrylate (MMA) in water is carried out with potassium persulfate as initiator. It is shown that the soapless emulsion polymerization of MMA gives different time-conversion and time-average molecular weight curves from those of bulk and emulsion polymerizations. Comparing the experimental results with those of the other types of polymerization, features of the rate of soapless emulsion polymerization are discussed and a kinetic model is proposed to apply the soapless emulsion polymerization of MMA in water. The experimental results can be well expressed by this model.     

反应性乳化剂在无皂硅溶胶苯丙乳液聚合中的应用

反应性乳化剂;硅溶胶;苯丙乳液;乳液聚合     

Radiation-induced emulsion polymerization of ethylene. II. Effect of potassium myristate concentration and dose rate on the rate of polymerization in connection with polymer properties,kinetics, and mechanism

Radiation-induced emulsion polymerization of ethylene with potassium myristate as an emulsifier was studied in connection with the kinetics and the mechanism. The molecular weight of polymer was relatively low, of the order of 10³, when a sufficient amount of emulsifier was used. However, polyethylene gel was produced in the absence of a sufficient amount of emulsifier. The rate of polymerization was proportional to the 0.5 power of dose rate and increased slightly with increasing emulsifier concentration. The rate of seeded polymerization followed a similar trend to that for conventional polymerization. Kinetic analysis of these results suggests that the escape of radicals produced by chain transfer of propagating radical with the emulsifier and the monomer from polymer particles into the aqueous phase plays an important part in the rate of polymerization. The melting temperature and the crystallinity of the polymer significantly decreased with increasing polymerization temperature in the range 40–60°C.     

Radical polymerization in homogenized butyl acrylate emulsion

The addition of a small amount of monomer strongly decreased the clouding temperature of nonionic emulsifier (Tween 20). The clouding temperature of the Tween 20 aqueous solution was independent of emulsifier concentration but it strongly varied in the presence of monomer. The decreased cloud temperature was attributed to the penetration of monomer molecules into the interfacial layer that increased the flocculation of microdroplets (monomer-swollen micelles). The surface tension of homogenized ((mini)emulsion) butyl acrylate aqueous emulsion was much smaller than that estimated at or above CMC of Tween 20. The polymerization rate vs. conversion curve of the (mini)emulsion deviates from the three rate intervals typical for the emulsion polymerisation. The shape of the rate-conversion curve reminds more the four rate intervals curve. Interval 2 is overlapped with the initial maximal rate and rate shoulder at higher conversion. The initial maximal polymerization rate (R_p,max,1) is attributed to the abrupt increase in polymer particles, the polymerization under monomer saturated condition and emulsifier containing peroxide groups (Tw_peroxid 20). The rate of emulsion polymerization of BA initiated by ammonium peroxodisulphate (APS) is ca. by one order of magnitude larger than that of blank polymerization (without APS). The second maximal rate (rate shoulder) can result from the gel effect. The more pronounced increase in R_p,max,1 with Tw 20 concentration supports the presence of peroxide groups. The slight dependence of R_p,max,2 on [Tw 20] for both APS and DBP (dibenzoyl peroxide) is discussed in terms of the depressed radical entry rate into the close packed surface later of polymer particles. The low activation energy is attributed to the decreased barrier for entering radicals into the polymer particles with increasing temperature. This is more pronounced with the accumulation of covalently bound emulsifier moieties (resulting from Tw_peroxid 20) at the particle surface. The ratio of the final number of polymer particles to the initial number of monomer droplets (N_p/N_drop) promotes the partial monomer droplet nucleation. The dye approach indicates that the degree of depletion of monomer droplets decreases from the classical emulsion polymerization to the polymerization in pre-homogenized emulsions and the emulsion polymerization with a prolonged-emulsification interval.     

Kinetics of the batch cationic emulsion polymerization of styrene: A comparative study with the anionic case

An in‐depth study on the kinetics of the cationic emulsion polymerization of styrene in a batch reactor is presented. This study is focused on the effect of the amount of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), using two different cationic initiators: 2,2′‐azobisisobutyramidine dihydrochloride (AIBA), 2,2′‐azobis (N,N′‐dimethyleneisobutyramidine) dihydrochloride (ADIBA), on kinetics and colloidal features such as conversion, number of particles, number average of radicals per particle, mean particle diameter, and particle size distribution (PSD) of the polystyrene latices obtained by emulsion polymerization in a batch reactor. Furthermore, the results of the cationic emulsion polymerization were compared with its homologous anionic case. Using DTAB as cationic surfactant an expected increase in the total rate of polymerization was observed when the DTAB concentration increased. However, the total number of particles increased much more than in the anionic system. On the other hand, a dependence on the particle size of the rate of polymerization per particle together with the average number of radicals per particle was found. These differences between cationic and anionic emulsion polymerizations were explained taking into account the limited particle coagulation observed with cationic surfactants, and the high rate of radical formation of cationic initiators. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4461–4478, 2006     

甲基丙烯酸丁酯微波无皂乳液聚合

以过硫酸钾作为引发剂进行了甲基丙烯酸丁酯的微波无皂化乳液聚合，讨论了单体浓度和引发剂用量对单体转化率，粒子粒径及其分布的影响，并与常规乳液聚合进行了比较。结果表明，通过微波无皂乳液聚合，乳胶粒子的粒径分布没有明显变化，但是聚合速率大为增加。     

KINETICS OF SUSPENDED EMULSION POLYMERIZATION OF METHYL METHACRYLATE

The kinetics of suspended emulsion polymerization of methyl methacrylate (MMA), in which water acted as the dispersed phase and the mixture of MMA and cyclohexane as the continuous phase, was investigated. It showed that the initial polymerization rate (Rp0) and steady-state polymerization rate (Rp) were proportional to the mass ratio between water and oil phase, and increased as the polymerization temperature, the potassium persulphate concentration ([I]) and the Tween20 emulsifier concentration ([S]) increased. The relationships between the polymerization rate and [I] and [S] were obtained as follows: Rp0 ∝ [I]0.73[S]0.32 and Rp ∝ [I]0.71[S]0.23. The above exponents were close to those obtained from normal MMA emulsion polymerization. It also showed that the average molecular weight of the resulting poly(methyl methacrylate) decreased as the polymerization temperature, [I] and [S] increased. Thus, MMA suspended emulsion polymerization could be considered as a combination of many miniature emulsion polymerizations proceeding in water drops and obeyed the classical kinetics of MMA emulsion polymerization.     

The decomposition of potassium persulphate used as initiator in emulsion polymerization

The decomposition rate of potassium persulphate in various aqueous solutions was measured by isotachophoresis using pure water, sodium dodecyl sulphate (SDS) solution, emulsifier-free polystyrene emulsion, SDS solution containing acrylamide monomer or an SDS-containing emulsion polymerization system for styrene. “Free” SDS molecules in the monomolecular dispersed state were found to increase markedly the decomposition rate, whereas those which formed micelles and became adsorbed onto polystyrene particles did not increase it. The acceleration phenomenon in the former case disappeared in the presence of a small amount of monomer.     

丙烯酸钠反相乳液聚合

以阴离子乳化剂制备丙烯酸钠反相乳液，用γ射线引发其聚合，用扫描电镜观测了聚合前后粒径的变化；并在聚合过程中改变剂量率观测了聚合速率的变化．这两个实验结果都显示聚合以液滴成核为主，即聚合机理类似于悬浮聚合．与以司盘８０为乳化剂的丙烯酸钠反相乳液聚合相比，体系与司盘体系的聚合动力学基本相似；但是体系中的分散液滴比司盘体系要大，结果使得在动力学上体系更类似于悬浮聚合的动力学．从聚合机理看，反相乳液聚合实际上就是粒子分散得比较小的反相悬浮聚合．     

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.     

Microemulsion polymerization of styrene in the presence of a cationic emulsifier

The principal subject discussed in the current paper is the radical polymerization of styrene in the three- and four component microemulsions stabilized by a cationic emulsifier. Polymerization in the o/w microemulsion is a new polymerization technique which allows to prepare the polymer latexes with the very high particle interface area and narrow particle size distribution. Polymers formed are very large with a very broad molecular weight distribution. In emulsion and microemulsion polymerizations, the reaction takes place in a large number of isolated loci dispersed in the continuous aqueous phase. However, in spite of the similarities between emulsion and microemulsion polymerization, there are large differences caused by the much larger amount of emulsifier in the latter process. In the emulsion polymerization there are three rate intervals. In the microemulsion polymerization only two reaction rate intervals are commonly detected: first, the polymerization rate increases rapidly with the reaction time and then decreases steadily. Essential features of microemulsion polymerization are as follows: (1) polymerization proceeds under non-stationary state conditions; (2) size and particle concentration increases throughout the course of polymerization; (3) chain-transfer to monomer/exit of transferred monomeric radical/radical re-entry events are operative; and (4) molecular weight is independent of conversion and distribution of resulting polymer is very broad. The number of microdroplets or monomer-starved micelles at higher conversion is high and they persist throughout the reaction. The high emulsifier/water ratio ensures that the emulsifier is undissociated and can penetrate into the microdroplets. The presence of a large amount of emulsifier strongly influences the reaction kinetics and the particle nucleation. The mixed mode particle nucleation is assumed to govern the polymerization process. At low emulsifier concentration the micellar nucleation is dominant while at a high emulsifier concentration the interaction-like homogeneous nucleation is operative. Furthermore, the paper is focused on the initiation and nucleation mechanisms, location of initiation locus, and growth and deactivation of latex particles. Furthermore, the relationship between kinetic and molecular weight parameters of the microemulsion polymerization process and colloidal (water/particle interface) parameters is discussed. In particular, we follow the effect of initiator and emulsifier type and concentration on the polymerization process. Besides, the effects of monomer concentration and additives are also evaluated.