高固含量聚合物乳液制备方法新进展

高固含量一直是聚合物乳液制备追求的目标 ,本文将高固含量 (>6 0 % )聚合物乳液的制备方法按机理分为控制乳胶粒直径分布 ,增大乳胶粒直径和使乳胶粒发生形变三类 ,详细评述了各种制备方法的研究进展 ,并对高固含量乳液制备的发展进行了展望。     

浓乳液双相聚合方法制备异形聚合物粒子

采用浓乳液双相聚合方法,成功制备了聚丙烯酸丁酯(PBA)的异形粒子,通过在连续相中引入聚合物隔层,大大提高了浓乳液聚合过程中的稳定性,探讨了隔层种类对浓乳液稳定性的影响,并研究了浓乳液分散相体积分数和交联剂用量对PBA粒子异形程度的影响,并结果表明,浓乳液双相聚合过程中,分散相体积分数越高,交联剂用量越高,PBA粒子的异形程度越大。     

高固含量低黏度丙烯酸酯乳液的制备及在密封胶中的应用

利用过硫酸铵-亚硫酸氢钠氧化还原引发体系制备了固含量为55%的丙烯酸乙酯、丙烯酸异辛酯、丙烯酸、甲基丙烯酸甲酯的共聚物种子乳液;以上述乳液为种子,十二烷基硫酸钠和辛基酚聚氧乙烯醚为乳化剂、碳酸氢钠为缓冲剂,过硫酸钾为引发剂80℃下制备固含量在70%~74%的高固含量、低黏度稳定乳液。种子乳液呈现多元分布、乳胶粒粒径约为150~300nm,增长后高固含量乳液仍保持宽分布、平均粒径大小在350~600nm,黏度在剪切速率20s-1时为600~900mPa·s。此乳液做成的密封胶固化时间短,收缩率小,强度大。     

超浓反相聚合物乳液的粒径双峰分布特征及其与稳定性的关系

以丙烯酸、丙烯酰胺、2-丙烯酰胺基-2-甲基丙磺酸作为混合单体,Span-80和Tween-60作为复合乳化剂、采用氧化还原引发体系在常温下引发聚合,制备了稳定的超浓反相聚合物乳液,同时制备了低分散相体积分数的普通乳液及由普通乳液离心得到的超浓反相聚合物乳液作为对比研究.用显微镜观察了乳胶粒的形态,统计计算了乳胶粒粒径...     

用电子显微镜研究有机硅氧烷乳液粒子的方法

乳液乃是一种多相体系,其中有一种液体以液珠形式均匀地分散于一个不和它相混合的液体之中。对有机硅氧烷(即硅油)乳液而言,就是硅氧烷以液珠形式(也称分散相)分散于水(连续相)中。在有机硅氧烷乳液的制备和应用过程中,一个极其重要的问题就是乳液的稳定性。研究乳液稳定性的方法很多,但是稳定性在很大程度上取决于硅油分散情况,硅油分散得愈细、愈均匀,即硅油粒子愈小,粒径分布愈     

高固含量低黏度聚氨酯微乳液的制备及性能研究

以聚(四氢呋喃-co-氧化丙烯)二醇(Ng210)为软段,异佛尔酮二异氰酸酯(IPDI)为硬段,以1,2-二羟基-3-丙磺酸钠(DHPS)和二羟甲基丙酸(DMPA)作为亲水扩链剂,采用自乳化法合成了一系列了高固含量低黏度稳定聚氨酯微乳液,分析了DHPS和DMPA质量配比对乳液性能的影响,结果表明,所得乳液粒径呈多元分布,乳胶粒子呈球形;乳液为假塑性流体,表观黏度小于250mPa.s(剪切速率为25s-1)且随切变速率的变化规律呈现一定的切力变稀特征;随着DHPS/DMPA比值的增大,胶粒平均粒径逐渐减小,多分散性增强;当DHPS/DMPA值为4/10～6/10时,乳液中大小粒子粒径比为6～8,且大乳胶粒子的体积分数约为70%～75%,乳液的固含量均大于70%.另外,乳液具有较好的低温和高温以及贮存稳定性,具有较低的表面张力,相对于常规的聚氨酯乳液,所制备的高固含量聚氨酯乳液胶膜具有更好的力学性能.     

高固含量乳液聚合中的表面活性技术研究进展

如何提高乳胶产品固含量及其性能一直是乳液制备工作所追求的重要目标。乳液聚合中可以使用各种乳化剂,也可不用乳化剂,但都必须使乳胶粒子表面具有亲水性即表面活性,因此,乳液聚合中的原理与技术实际上可以归结为使乳胶粒子表面具有亲水性即表面活性技术。各种研究表明,采用不同乳化剂和表面活性技术所制备的乳胶性能差别很大,合适有效的表面活性技术不仅大幅度提高聚合物乳液的性能,还可以缩短反应时间,简化制备工艺。本文详细评述了近几年来高固含量乳液聚合中常规乳化剂、可聚合乳化剂、复合乳化剂和表面活性单体及其与之相应的表面活性技术的研究现状,并对高固含量乳液乳化剂的发展进行了展望。     

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.     

油酸-正丙醇-水无表面活性剂反相微乳液电导研究

本文对油酸-正丙醇-水三元体系的相行为进行了研究,表明可形成微乳液.由于体系中无传统表面活性剂,故所形成的微乳液为无表面活性剂微乳液.在反相微乳液区,固定正丙醇/油酸体积比(RP/O)为3∶5、1∶1和2∶1,考察了体系电导率(κ)随分散相体积分数(φd)的变化,结果表明κ随φd的增大先缓慢增加,后急剧增大,符合渗滤特...     

非相容聚合物体系熔融共混过程中分散相粒径变化的预测

以PS PP共混体系为研究对象 ,研究了非相容聚合物体系混炼过程中分散相含量、剪切速率及聚合物弹性等对分散相粒径变化的影响 ,对平衡态分散相粒径的变化进行了预测 ,并对其计算公式进行了新的改进 .研究表明 ,分散相浓度较低时 ,分散相粒径与分散相体积分数呈线性增长关系 ;在较高浓度时 ,分散相粒子的聚结作用明显 ,公式应加以修正 .实验中还观察到 ,对于PS(连续相 ) PP(分散相 )共混体系 ,随着剪切速率的增大 ,分散相粒径先不断减小 ,达到一极小值后 ,却又有所增大     

Formulation development of a filter-sterilizable lipid emulsion for lipophilic KW-3902, a newly synthesized adenosine A1-receptor antagonist

KW-3902 (a newly synthesized adenosine A1-receptor antagonist) has potent diuretic and renal protective activities. The objective of the present study was to develop an injectable formulation of KW-3902, that was water-insoluble and less than 1 microg/ml, and so lipid emulsion was selected as a favorable formulation. Changing the mixing ratio of oil to lecithin, the particle size of the lipid emulsion was controlled, and by adjusting the mixing ratio of oil/lecithin=1:1, the weight ratio, a lipid emulsion with a mean particle size of 130 nm was prepared. This small particle size makes this emulsion filter-sterilizable, which is a favorable feature for heat labile products. The stability of the KW-3902 lipid emulsion was assessed from the viewpoint of the electrostatic repulsion, and by including the oleic acid a stable lipid emulsion was developed, which was stable for at least 12 months at 10 and 25 degrees C and for 3 months at 40 degrees C. The feature of this small particle size emulsion was also characterized by comparing it with a conventional emulsion (oil/lecithin=1:0.12, the weight ratio, particle size is 220 nm). The release of KW-3902 from the oil particles was measured and the apparent permeability of KW-3902 was calculated from the equation according to Fick's theory. The apparent permeability, P, of KW-3902 was not affected by the particle size of the emulsion (1.78x10(-11) cm/s for the small emulsion and 1.76x10(-11)cm/s for the conventional emulsion). The distribution mode of KW-3902 in the lipid emulsion was also discussed by considering the findings of the permeability and solubility of KW-3902.     

Emulsion particle size in porous media and its effect on the displacement efficiency

The emulsification process in reservoirs was simulated using core displacement experiments. Emulsions with different particle sizes were prepared using different permeability cores, and the different emulsion particle sizes formed using different permeability cores were studied. The emulsion particle size was graded against the core throat diameter, and the displacement efficiency of the different particle size emulsions was studied. The displacement mechanism of the emulsion was analyzed. The results indicated that the emulsion is mostly pore-throat scale formed in the porous media, with a particle size distribution similar to that of the core throat diameter, and the emulsion particle size increases with the increase of core permeability. The recovery percentage of emulsion flooding is greater when the matching ability of the emulsion was favorable, it is 17.07% when the matching factor is 1.08. The pore-throat scale emulsion can block high permeability zones and expand sweep volume. Moreover, due to deformation of the emulsion, the elastic stress can make the residual oil migrate forward and improve the efficiency of oil displacement.     

Effects of Paraffin Emulsion on the Structure and Properties of Soy Protein Films

In this work, the water-repellent capacity of the paraffin emulsion?covered soy flour (SF) substrate has been studied. Effect of paraffin emulsion content on the structure and properties of the resulting films were studied using laser particle size distribution analyzer, water absorption test, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and tensile testing. Study on the emulsion particle size and stability revealed that the particle size distribution and stability were strongly dependent on the pH of the system. And the optimum pH was 9.9. The incorporation of paraffin emulsion produced at pH 9.9 could markedly enhance the water resistance of films. However, the improvement was realized at the expense of decreased thermal stability and tensile strength of SF?paraffin emulsion films. The addition of paraffin emulsion could destroy the crystalline domains of soy protein and change the protein secondary structure.     

Determining the temperature dependence of the emulsion particle size of polyacrylate core–shell and polystyrene by photon correlation spectroscopy

The dependence of the particle size of a polyacrylate core-shell emulsion on temperature has been investigated in the temperature range of 10–55°C by photon correlation spectroscopy. To compare, the dependence of the particle size of an aqueous suspension of a polystyrene standard on temperature has been also investigated under the same conditions. This showed that as the temperature increases, the particle size of both samples decreases, but the rate of size decrease of the polystyrene standard is larger than that of the polyacrylate core–shell emulsion. By linear regression analysis, two regression equations of both samples have been set up. Furthermore, the apparent moving activation energy has been worked out from the size–temperature data.     

Cellulose gel dispersions: fascinating green particles for the stabilization of oil/water Pickering emulsion

A facile approach for the preparation of cellulose gel dispersions with particle size less than 5 μm has been developed. The particles were obtained by dissolving cellulose in NaOH/urea solvent, followed by regeneration in ethanol/H₂O mixed solution with homogenizer shearing. The characteristics of the cellulose gel dispersions were evaluated in terms of particle dimensions and crystalline structure, size distribution and rheology behavior. The cellulose gel dispersions had low crystallinity, and the concentration of the cellulose solution had little influence on the particle size of the gel dispersions. Furthermore, the cellulose gel dispersions could be well dispersed in deionized water, and they could be used to stabilize oil/water emulsion without addition of any surfactant. The formed Pickering emulsion had typical shear-thinning behavior and higher storage modulus. The concentration of cellulose gel dispersions had a significant influence on the emulsion stability. The Pickering emulsion stabilized by the cellulose gel dispersions would open opportunities for the development of food emulsion systems or environmentally friendly functional materials.     

DETERMINATION OF LONG-TERM STABILITY OF VITAMIN E EMULSION AND FORMATION OF MICROEMULSIONS BY USING LASER LIGHT SCATTERING AND UV ABSORPTION MEASUREMENTS

This paper presents methods of determining the long-term stability of vitamin E emulsion and formation of microemulsions. Several emulsion systems formed by using anionic, zwitterionic and cationic surfactants have been studied in the presence and absence of NaCI. Several conclusions can be drawn: (1) by using UV absorption and particle size measurements, one may be able to predict the long-term stability of an emulsion or the possibility of forming a microemulsion by measuring the initial properties of an emulsion, (2) in order to form a stable vitamin E emulsion or microemulsion, the initial properties of the emulsion should have the following features : (a) the particle size is ≤ 200 nm, (b) the surfactant system has a saturation value ≥ 1 and (c) the surfactant system can dissolve a substantial amount of vitamin E without causing an increase of the emulsion droplet size and (3) the saturation value and the stability of many vitamin E emulsion systems can be increased by adding an optimum amount of NaCI.     

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制备方法对乳液性质的影响

采用自由基引发剂用３种不同的聚合方法制备了新型的含氢聚甲基硅氧烷（ＰＨＭＳ）／丙烯酸丁酯（ＢＡ）／羟甲基丙烯酰胺（ＮＭＡ）复合聚合物乳液。详细讨论了不同聚合方法对乳液稳定性和乳胶粒子的影响，同时对聚合反应的机理、产物的结构作了考察．结果表明：通过乳液聚合，得到了ＰＨＭＳ／ＢＡ／ＮＭＡ共聚物；单体乳液滴加法所得乳液粒径较小，乳液性能稳定，是制备ＰＨＭＳ／ＢＡ／ＮＭＡ复合聚合物乳液较适宜的方法．     

Prediction of emulsion particle sizes using a computational fluid dynamics approach

For many food products emulsification processes play an important role. Examples are ice cream, spreads, sauces, etc. As is well known, droplet break-up and coalescence phenomena are the local processes underlying the control of particle size in an emulsion process. Quite a number of studies have generated scaling laws which can be easily applied and which are useful in the design of a process. However, the prediction of particle sizes in an inhomogeneous flow, where the flow velocity is changing spatially in strength and direction and with time, is not yet well established. For one-phase flows computational fluid dynamics (CFD) methodologies are in use to predict details on the flow with quite some success. This methodology has been extended to capture the dispersed phase in an efficient way. The essence is that break-up and coalescence processes determine source terms in a transport equation for the moments of the particle size distribution, while velocity vectors as obtained in the one-phase CFD simulation determine the convective term. This method allows particle size prediction in any equipment. The approach is illustrated for the particle size evolution of an oil-in-water emulsion, for a phase-separated biopolymeric mixture (a so-called water-in-water emulsion) and for the escape of the included oil droplets from a double emulsion of the type oil-in-water-in-oil. In all cases experimental results are compared with simulation results, which match very well. This shows the strength of the method.     

Transition from microemulsion to emulsion polymerization: Mechanism and final properties

Microemulsion and emulsion polymerization can have some similarities in starting conditions and polymerization mechanisms, but the resulting latices are unalike in particle size and molecular weight. Here we show that polymerizations can be formulated that display the characteristics often separately associated with microemulsion or emulsion polymerization. Kinetic modeling and particle size measurements show that emulsion polymerizations with initial concentrations close to the microemulsion–emulsion phase boundary demonstrate relatively fast consumption of monomer droplets and produce smaller particles. Because of their high surfactant concentrations, none of the emulsion polymerizations examined demonstrate the classical Smith–Ewart kinetics usually associated with emulsion polymerization. Instead these emulsion polymerizations have a long period of particle nucleation that subsides only after the disappearance of monomer droplets. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5253–5261, 2004     

Preaparation of cationic latexes of poly(styrene-CO-butyl acrylate) and their properties evolution in latex dilution

Cationic latexes were prepared through emulsion copolymerization of styrene(St) and butyl acrylate(BA) with a cationic surfactant,cetyl trimethyl ammonium bromide(CTAB).Latex properties,including particle size,size distribution,ζpotential,surface tension and monomer conversion,were determined for latexes prepared with different CTAB amounts. Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation.Results showed that both particle size andζpotential were function of polymerization time and latex solids.Parallel emulsion polymerizations with cationic,anionic charged initiator and charge-free initiators were also carried out,the latex properties were determined at different polymerization time.All these results were attentively interpreted based on the mechanisms of emulsion polymerization,surfactant adsorption and latex particle stabilization.