不完全相反转乳化过程分散相水滴形态发展研究

相反转乳化技术是制备高分子树脂水基分散体系的新方法[1～4].相反转指多组分体系(如油/水/乳化剂)中的连续相在一定条件下相互转化的过程,如在油/水/乳化剂体系中,其连续相由水相向油相(或从油相变为水相)的转变.在连续相转变区,体系的界面张力最低,因而分散相的尺寸最小.同理,可利用相反转技术直接将高分子树脂乳化为尺寸很小的水基微粒,即制备高分子树脂的水基分散体系.由于高分子树脂的粘弹性及相反转过程的复杂性,对高分子树脂的相反转乳化过程的机理研究较少.杨振忠[5]等通过调节高分子非离子型乳化剂浓度,可以有效地控制相反转完善程…     

无皂相反转乳化法制备高分子水基分散体系

高分子树脂水基分散体系是指高分子树脂以微粒形式分散于水中 ,包括高分子乳液、高分子悬浮液等体系 .由于高分子树脂水基分散体系具有低成本 ,高性能 ,无污染等优点 ,一直受到普遍关注 .高分子树脂乳液一般通过乳液聚合制备 .该方法只适用于由含双键的单体制备的加聚产物 .而在制备缩聚产物的乳液时 ,乳液聚合方法局限性很大 ,而最近发展起来的相反转乳化技术 ,适用于制备包括加聚产物和缩聚产物在内的大多数高分子水基分散体系 ,拓宽了高聚物水基分散体系的范围 [1] .杨振忠等 [2～ 5] 利用相反转乳化技术制备了未固化和可固化的环氧树脂…     

双酚A型环氧树脂水基化微粒分析

高分子树脂水基化微粒化就是使高分子树脂以微粒形式分散于水中,高分子乳液、悬浮液都属于此范畴．因其不含有机溶剂,且具有无环境污染及不易失火等优点,放这方面的研究正成为高分子技术的一个研究热点．通常的乳液聚合或悬浮聚合方法是从小分子单体到聚合物水基化体系的化学反应过程,一般只适于制备加聚物的水基化体系,而不适用于制备维聚物的水基化体系．本文提出的相反转技术是一种有效的制备高分子水基化体系的方法,它能将几乎所有的高分子树脂通过物理的乳化方法制成相应的水基化体系[1,2],大大拓宽了其制备范围．相反转[3。4]…     

环氧树脂相反转乳化过程相态发展研究

以扫描电镜为主要手段,观察了环氧树脂相反转乳化过程中的相态演化过程.结果表明:在较高乳化剂浓度下,当水含量达到某一临界值时,原W/O体系中水滴间的相互吸引大于水滴间的排斥作用,导致相邻水滴同时快速地融合为连续相并得到水基微粒,水基微粒的尺寸较小,约为亚微米级,尺寸分布窄,微粒为单个粒子.在乳化剂浓度较低情况下,非相邻较大水滴在剪切场作用下随机地融合为连续相,发生不完全相反转,并得到W/O/W结构,水基微粒尺寸较大,约10微米数量级,尺寸分布宽且为一种复合多孔结构.此外,分析了相反转发展演变过程.     

环氧树脂相反转乳化过程相态发展研究＊

以扫描电镜为主要手段,观察了环氧树脂相反转乳化过程中的相态演化过程.结果表明 在较高乳化剂浓度下, 当水含量达到某一临界值时, 原W/O体系中水滴间的相互吸引大于水滴间的排斥作用, 导致相邻水滴同时快速地融合为连续相并得到水基微粒, 水基微粒的尺寸较小, 约为亚微米级, 尺寸分布窄,微粒为单个粒子.在乳化剂浓度较低情况下,非相邻较大水滴在剪切场作用下随机地融合为连续相,发生不完全相反转, 并得到W/O/W 结构, 水基微粒尺寸较大,约10微米数量级,尺寸分布宽且为一种复合多孔结构.此外,分析了相反转发展演变过程.     

制备高分子水基微粒体系的相反转技术

高分子树脂的微粒化水基化体系具有广阔的应用前途，正引起人们极大关上方面技术能把几乎所有的高分子树脂乳化为微粒化水基化体系，具有很宽的应用范围，本文简要地从相反转技术的发展，相反转模式，相反转类型，相反转的理论处理等４方面作以介绍。     

高分子水基微粒形态与界面膜性质的关系

高分子水基微粒形态与界面膜性质的关系杨振忠赵得禄许元泽徐懋（中国科学院化学研究所高分子物理开放实验室北京１０００８０）关键词高分子树脂，相反转，水基微粒，界面膜相反转技术是制备高分子树脂微粒化水基化体系的新方法［１］，正成为高分子技术的一个热门方向...     

环氧树脂水基分散体系的相反转乳化

以聚乙二醇－邻苯二甲酸酐－环氧树脂Ｅ－４４多元嵌段共聚体为乳化剂,将环氧树脂Ｅ－４乳化成水包油的稳定水基乳液。用乳液体系电导率和粘度的变化表征了相反转乳化过程。研究了乳化剂浓度、三元多嵌段共聚体中亲水嵌段分子量和乳化温度对相反转乳化过程的影响。实验结果表明,体系在较高乳化剂浓度（９．１％）下为完全相反转,在低乳化剂浓度（４．１％）下为不完全相反转。相反转时水与环氧树脂Ｅ－４４的重量比值随乳化剂浓度     

相反转技术制备环氧树脂水基体系——相反转过程的流变行为研究

对高乳化剂浓度下的相反转发展过程的流变行为进行了应力扫描、动态频率扫描实验表征．结果表明，乳化剂浓度较高时，体系发生完全相反转；体系在相反转点前为Ｗ／Ｏ结构，其粘度几乎不随剪切应力的改变而改变，表现为牛顿流体行为；体系在相反转点后为Ｏ／Ｗ结构，具有很高的粘弹性，并且在较高剪切应力下表现为典型的假塑性．这是由于高分子水基微粒间通过其表面覆盖的表面活性剂与水形成氢键而产生了一种静态结构，此结构在较高剪切应力作用下破坏而导致假塑性．     

无皂相反转乳化法制备高分子水基分散体系

高分子树脂水基分散体系是指高分子树脂以微粒形式分散于水中, 包括高分子乳液、高分子悬浮液等体系. 由于高分子树脂水基分散体系具有低成本, 高性能, 无污染等优点, 一直受到普遍关注.     

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.     

不完全相反转发展过程的流变行为

以动态应力流变仪ＤＳＲ（ＤｙｎａｍｉｃＳｔｒｅｓＲｈｅｏｍｅｔｅｒ）对双酚Ａ型环氧树脂在低乳化剂浓度（２３３ｗｔ％）下的相反转乳化过程进行了稳态应力扫描及动态频率扫描实验．实验结果表明,体系在相反转点前表现为牛顿流体行为,粘度几乎不变;相反转点时,体系粘度增加幅度很小,体系的有关动态流变参数（剪切储能模量、损耗模量和复数粘度）均出现极小值,将此归于局部连续水相的润滑作用;进一步加水,体系的动态流变量增加,意味着相反转在相反转点后仍在继续进行．所以,体系在低乳化剂浓度时,发生了不完全相反转．     

Preparation of waterborne dispersions of epoxy resin by the phase-inversion emulsification technique. 1. Experimental study on the phase-inversion process

 Waterborne dispersions of bisphenol A epoxy resin were prepared by the so-called phase-inversion emulsification technique. The electrical properties, rheological behavior and morphological evolution during the phase inversion process were characterized systematically. It was shown that both emulsifier concentration and emulsification temperature play great roles in controlling the phase inversion process as well as the structural features of the waterborne particles. A high emulsifier concentration, i.e. 10.90 wt% and a low emulsification temperature, i.e. 73 °C, facilitate complete phase inversion, in which all water droplets in the system are simultaneously transformed into the continuous phase at the phase-inversion point (PIP). In this case, sub-micron-sized, discrete waterborne particles were formed. In contrast, a complex water-in-oil-in-water structure was achieved by incomplete phase inversion at a low emulsifier concentration, i.e. 2.33 wt%, and a high temperature of 80 °C. The morphological evolution observed by scanning electron microscopy revealed that not all the water droplets in the system were converted into the continuous phase at the PIP and that some small water drops were trapped within the waterborne structure. Received: 15 March 2000/Accepted: 16 May 2000     

Preparation of waterborne dispersions of epoxy resin by the phase-inversion emulsification technique. 2. Theoretical consideration of the phase-inversion process

 A theoretical consideration of the phase-inversion technique to prepare waterborne particles based on the experimental facts of the phase inversion process given in part 1 of this series is presented. The deformation and breakup of the water droplets dispersed in an epoxy resin phase under shear action are analyzed in terms of microrheology. The interaction and coalescence dynamics among the water droplets stabilized by an interfacial layer formed by the emulsifier molecules are discussed in terms of Derjaguin–Landau–Verwey–Overbeek theory and effective collision theory, respectively. A criterion for the completion of phase-inversion is that the attraction among the water droplets exceeds the entropic repulsion. Thus, a physical model of phase-inversion is proposed to predict the effects of some control variables on the phase-inversion process as well as the structural features of the waterborne particles, by which the experimental results could be well interpreted. It is indicated that the achievement of phase inversion is determined by the dynamic coalescence among the water droplets before the phase-inversion point (PIP). If the dynamic coalescence among the water droplets is ignored, phase inversion is achieved completely and sub- micron-sized particles are prepared. In comparison, if the dynamic coalescence is significant, phase inversion is achieved incompletely and a large complex water-in-oil-in-water structure is prepared. In the case of complete phase inversion, it is shown that the size of the waterborne particles is comparable with the size of the water droplets before the PIP. Received: 15 March 2000/Accepted: 16 May 2000     

影响环氧树脂E-44相反转乳化的因素

研究了乳化剂的HLB值、乳化剂浓度、乳化温度、搅拌强度对环氧树脂E-44相反转乳化中临界含水量Rf值与乳状液稳定性的影响,探讨了环氧树脂E-44相反转机理。实验结果表明环氧树脂E-44从W/O向O/W相反转的发生与乳化剂的HLB值与浓度、乳化温度、搅拌强度等因素都有关,其Rf值随着乳化条件的不同是动态变化的。     

Effect of diutan microbial polysaccharide on the stability and rheological properties of O/W nanoemulsions formed with a blend of Span20-Tween20

The stability and rheological behavior of oil-in-water (O/W) nano-emulsions formed with a blend of Span20-Tween20 have been studied with and without diutan microbial polysaccharide. It is found that there exist thresholds for the water content and emulsifier to obtain stable nano-emulsions using the emulsion inversion phase (EIP) method. The viscosity of the nano-emulsion is proportional to the emulsifier content and inversely proportional to the water content. High emulsifier content is not conducive to the thermal stability of the nano-emulsion. The addition of diutan gum with negative charge into the nano-emulsions increases the electrostatic repulsion between droplets and makes the droplet size smaller and more unifom, slowing down the coalescence and Ostwald ripening of the nano-emulsions. Due to the association of the diutan gum double helix, a three-dimensional network structure is formed in the continuous phase of nano-emulsions, which improves the stability of nano-emulsions and is also the main factor giving the nano-emulsion high viscoelasticity at high temperature. This study offers new insight into the nano-emulsion containing microbial polysaccharide and may serve as a guideline for practical applications of new nano-emulsion systems.