Modeling the effect of mixed emulsifier systems in emulsion copolymerization

A mathematical model for the emulsion copolymerization of methyl methacrylate and butyl acrylate has been developed. This model, which applies the method of moments of a distribution to model the evolution of the particle size distribution, predicts the effects of the concentration and composition of anionic/nonionic surfactant systems on the polymerization process and on the characteristics of the product obtained, including particle nucleation, growth, and coagulation. Nucleation is a dynamic process in which the surfactant system affects the competition between homogeneous and heterogeneous nucleation, with simultaneous coagulative processes of precursor particles. The effect of the surfactant system on nucleation is described mathematically using a variable radical critical chain length, j_cr. The solution properties of surfactant mixtures, mainly critical micelle concentration and micelle composition, were predicted using the thermodynamics of nonideal mixtures. A good agreement between model predictions in batch and semicontinuous reactors and experimental results was found. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 445–458, 1997     

Effect of organic surfactant additives on gas holdup in the pseudo-homogeneous regime in bubble columns equipped with fine pore sparger

New experimental data concerning the gas holdup in bubble columns equipped with porous sparger were acquired. The effect of surfactant additives on gas holdup in the pseudo-homogeneous regime has been studied. Three different commercial surfactants (Triton X-100^®, SDS^®, CTAB^®) were used and four aqueous solutions of each one were employed, in order to study the effect of the surfactant concentration and type (i.e., non-ionic, anionic, cationic). A general correlation, which includes dimensionless numbers (i.e., Froude, Archimedes and Bond) as well as the geometric characteristics of the column and the sparger, can predict the gas holdup in various systems (i.e., pure substances, ionic surfactants, non-ionic surfactants) with reasonable accuracy.     

The stabilization effect of mixed-surfactants in the emulsion polymerization of styrene

Summary The emulsion polymerization of styrene was performed at 50°C with a mixture of anionic and nonionic surfactants using different surfactant concentrations. In the single-surfactant systems, a proportional relationship was observed between the total particle surface area per cm³ of aqueous solution at 90% conversion (TS) and the amount of surfactant used for each polymerization. For mixed-surfactant systems an additivity was established between the TS value and surfactant composition. The study of the particle size data from low to high conversion showed that the particle number changed with conversion.     

Acrylic latices stabilized by polymerizable non-ionic surfactant

The final latex particle size is controlled by the concentration of polymerizable non-ionic surfactant NE-40 in the emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The particle size decreases with increasing NE-40 concentration and increases with increasing persulphate initiator concentration. The dependence of particle size on the initiator concentration does not follow conventional Smith–Ewart theory, which is attributed to the bridging flocculation process during the particle nucleation period. The differences in the particle nucleation and growth stages and colloidal stability observed in the NE-40 and nonyl phenol-40 mol ethylene oxide adduct (NP-40) stabilized systems can be attributed to the different distribution patterns of surfactant molecules in the particles. Experimental data also indicate that the particle size decreases with increasing electrolyte concentration, or agitation speed. The total scrap, presumably caused by the bridging flocculation process, increases rapidly with increase in the NaCl concentration The amount of large flocs formed during polymerization is generally greater for the run operated at higher agitation speed. As expected, the latex products stabilized by non-ionic surfactants show excellent stability toward added sodium salt.     

Monomer-micelle equilibrium in the diffusion of surfactants in binary systems through collagen films

Three different binary systems (two anionic/nonionic and one anionic/amphoteric) were selected to study the behavior of these mixtures in their diffusion through a collagen film and the formation of micelle aggregates in such systems. The inhibition observed in the surfactant diffusion of anionic/nonionic and anionic/amphoteric binary mixtures through a collagen film, in comparison with that of single surfactants, has been related to the behavior of these binary systems in the micellization process. The surfactant flux in these systems is mainly determined by the monomeric species. The modification of the equilibrium monomers-micelle aggregates shown by these surfactant binary systems could be also associated with the reduction of the irritancy power for such binary systems.     

Preparation of nanometer-sized barium titanate powders by a sol-precipitation process with surfactants

Nanometer sized barium titanate powders can be obtained by adding surfactants to titanyl acylate precursors in a strong alkaline solution (pH>13). FTIR, TGA, SEM and XRD were used to investigate the effects of the surfactants influence on the morphology of the obtained titanate powders and their sinterability. In a pre-added surfactant process (i.e. surfactant added before precipitation in alkaline solution), a slower rate of hydrolyzation is observed, and the shift rate in the condensation is slower. Less crosslinking of smaller particles is observed. The addition of anionic surfactant (LAS) in general leads to the formation of micelles, which control the nucleation and crystal growth of the titanate powders. This micelle formation results in a smaller particle size (30–90 nm), and a larger surface area of 60.5 m²/g for BaTiO₃ powders was obtained. The nanometer-sized barium titanate powders were readily sintered at 1100–1200 °C.     

Soil deposition on shrink-resist-treated wool fabrics in the presence of anionic and non-ionic surfactants

The deposition behaviour of carbon black on shrink-resist-treated wool fabric, and on untreated wool, in the presence of different mixtures of anionic and non-ionic surfactants has been investigated. Two types of surfactant mixtures were studied; sodium dodecylbenzenesulphonate and sodium dioctylsulphosuccinate were used as anionic surfactants and Triton X-100 as a non-ionic surfactant. An electrokinetic study was also carried out, under similar conditions; the zeta potential was obtained, which was related to the amount of deposition found. From these zeta potential measurements the surface charge density was determined.     

Influence of surfactants on properties of electrochemically synthesized pyrrole/1-dimethylaminopyrrole copolymer

The electrochemical copolymerization of pyrrole (Py) and 1-dimethylaminopyrrole (DMAPy) was successfully carried out in the presence of three different types of surfactant (anionic, cationic and non-ionic) by cyclic voltammetric method. The influence of anionic (sodium dodecylbenzenesulfonate) (NaDBS), cationic (tetradecyltrimethylammonium bromide) and non-ionic poly(ethylene oxide)(10) iso-octylphenyl ether (Tween 20) surfactants on the properties of copolymer was investigated. The copolymer has been characterized by the cyclic voltammetry, fourier transform infrared spectroscopy, UV–Vis spectroscopy, scanning electron microscopy, thermogravimetric analysis and conductivity measurements. The results confirmed that the electrochemical reaction of Py and DMAPy in the presence of surfactants generated copolymers. The type of surfactant had an effect on the structural, morphological, thermal and conductivity properties of the copolymers in different ways. According to the initial decomposition temperatures, the thermal stability of the copolymers improved in the presence of surfactants. Py/DMAPy copolymer synthesized in the presence of anionic surfactant NaDBS had the highest initial decomposition temperature (320 °C). The copolymer prepared using various surfactants exhibited different morphologies. The electrical conductivity of pyrrole/1-dimethylaminopyrrole copolymer (8.39 × 10^?3 Scm^?1) was improved using surfactants, especially with anionic surfactant (3.75 × 10^?2 Scm^?1) due to the incorporation of NaDBS into the PPy polymer chain that resulted in a more compact morphology and reduced size of PPy globules.     

Modelling particle size distributions and secondary particle formation in emulsion polymerisation

An extensive model is given for the particle size distribution (PSD), particle number, particle size and amount of secondary nucleation in emulsion polymerisations. This incorporates what are thought to be all of the complex competing processes: aqueous phase kinetics for all radical species arising from both initiator and from exit (desorption), radical balance inside the particles, particle formation by both micellar and homogeneous nucleation mechanisms, and coagulation (the rate of which is obtained using the Healy–Hogg extension of DLVO theory). The predictions of the model are compared to extensive experimental results on rates, time evolution of the particle size distribution, and relative amounts of secondary nucleation, for styrene initiated by persulfate with sodium dodecyl sulfate and with sodium dihexyl sulfosuccinate as surfactants. For this system values of almost all of the many parameters needed for the model are available from independent measurements, and thus no significant parameter adjustment is plausible. Accord with experiment is imperfect but quite acceptable, supporting the validity of the various mechanisms in the model. Effects such as the experimental variation of particle number with ionic strength, as well as calculated coagulation rate coefficients as functions of particle size, suggest that coagulation of precursor (i.e., newly-formed) particles is a significant effect, even above the cmc. The modelling also suggests why secondary nucleation occurs readily in systems stabilised with polymeric surfactant.     

Compound surfactant-based emulsion method for the preparation of high-porosity alumina microspheres

Porous alumina microspheres have attracted significant attention owing to their high mechanical strength and excellent chemical and thermal stability. The emulsion method is considered as a simple and controllable method for the preparation of inorganic microspheres. However, preparing alumina microspheres with the emulsion method is challenging because the emulsification of the precursor is inhibited by the rapid hydrolysis of aluminum alkoxide. Herein, we report a new emulsion method for the preparation of high-porosity alumina microspheres using a combination of ionic and non-ionic surfactants; in this method, the compound surfactants act as a template agent to guide aluminum alkoxide to form a lamellar structure through self-assembly. The decomposition of the templating agent and transformation of the alumina crystal at a high temperature result in structural collapse and formation of lamellar pores. Compound surfactants increased the spheroidization rate of the emulsion from 47% to 63% after hydrolysis, whereas the particle size was decreased by almost half. Additionally, the morphology and porosity of the alumina microspheres were changed. With increasing anionic surfactant content, the porosity increased initially and then decreased. The porosity of the alumina microspheres reached a maximum value of 76% at the 1:1 mass ratio of the non-ionic to anionic surfactants. Heat treatment was found to change the size of lamellar pores, with the pore diameter reaching maximum value at 1300 °C. The compound surfactants also increased the compressive stress and specific surface area of the porous alumina microspheres.     

Adsorption of surfactants from water onto raw and HCl-activated clays in fixed beds

The removal of surfactants from water by adsorption onto raw and HCl-activated montmorillonite in fixed beds was studied. Three surfactants hexadecylpyridinium chloride (cationic), sodium dodecyl sulfate (anionic), and Triton X-102 (non-ionic) were selected in the concentration ranges lower than their critical micelle concentrations in fixed bed experiments. It was shown that the adsorption of anionic surfactant onto Ca-montmorillonite (SAz-1) decreased with increasing pH but that of cationic surfactant increased. The adsorption capacity of non-ionic surfactant was maximized at pH 7.0. For given clay, the adsorption capacities of surfactants were strongly pH-dependent. The adsorption capacity and adsorption rate of non-ionic surfactant onto SAz-1 could be largely improved after acid activation of the clay. Such an improvement was due to the fact that the dissolution of Al³⁺ or Fe²⁺ of montmorillonite occurs in acid solution. The calculated breakthrough curves in fixed bed agreed with the measured ones (standard deviation < 6%). The 50% C/C₀ breakthrough time (τ) decreased with increasing liquid flow rate. The effects of flow rate on the adsorption constant and adsorption capacity were also discussed.     

Particle nucleation rates in continuous emulsion polymerisation reactors

The design of a continuous, stirred emulsion polymerisation reactor requires a detailed characterisation of the particle nucleation rate. Here, consideration is given to systems which use micelle-forming surfactants and water-insoluble monomers. The surfactant micelles will be considered to participate in two competing rate processes; the nucleation of polymer particles and dissolution into the aqueous phase. When the reactor operates in a steady state it is possible to obtain a size distribution function for the particles. This distribution function is used in the development of a number of diffusion equations and conservation equations. By making various sets of assumptions concerning the nucleation process, these equations are then used to obtain expressions for the particle number. By comparing the different models with experimental results it can be seen that satisfactory predictions for the particle number can be obtained without assuming that the polymer particles are always saturated with surfactant. The models also show that the radical absorption processes are not controlled by diffusion in the aqueous phase. In some cases the particle number does not reach a steady state but oscillates with time. The nature of these oscillations is described by the solution of nonlinear differential equations. Boundary conditions for these equations depend on the reaction conditions.     

宜昌磷矿低温捕收剂研究

以高品位胶磷矿为研究对象,采用来源广泛且价格便宜的棉油皂脚工业品作主体药剂,在单泡管中进行了增效剂(阴离子、阳离子和非离子型表面活性剂)的筛选试验。结果表明:阴离子型表面活性剂(SDS、十二烷基磺酸钠、SDBS)的用量增加,胶磷矿的产率增加,具有良好的增效作用;非离子型表面活性剂(磷酸二(2-乙基己基)酯、吡啶)须控制用量,过量则增效作用降低。本研究还进行了验证试验,当pH=8、浮选温度为10～12℃时,SDS只需添加皂脚用量5%,精矿的回收率可提高30.68%,并能降低对温度的敏感程度,为胶磷矿低温捕收剂的进一步应用打下良好的基础。     

Combined Use of Ozonation and Biodegradation of Anionic and Non-ionic Surfactants

This study investigated the extent of primary and final biodegradation of anionic and non-ionic surfactants to evaluate the combined use of ozonation and biodegradation in surfactant removal. The surfactants used were alkylpolyglucosides and linear alkyl benzene sulfonates. The anionic surfactant containing a benzene ring on its structure was oxidized faster than was the non-ionic surfactant. Both surfactants showed poor mineralization due to ozonation indicating an ozone attack primarily on carbon bonds. The results indicate that the removal of surfactants and of the total organic carbon is increased by the consecutive use of ozonation and biodegradation.     

Synergism and Performance for Systems Containing Binary Mixtures of Anionic/Cationic Surfactants for Enhanced Oil Recovery

The surfactant structure–performance relationship and application properties in enhanced oil recovery (EOR) for binary mixtures of anionic and cationic surfactants are presented and discussed. A polyoxyethylene ether carboxylate anionic surfactant was blended with a quaternary ammonium chloride cationic surfactant and tested for a high-temperature, low-salinity, and high-hardness condition as found in an oil reservoir. These mixtures were tailored by phase behavior tests to form optimal microemulsions with normal octane (n-C8) and crude oil having an API gravity of 48.05°. The ethoxy number of the polyoxyethylene carboxylate anionic surfactant and the chain length of the cationic surfactant were tuned to find an optimal surfactant blend. Interfacial tensions with n-C8 and with crude oil were measured. Synergism between anionic and cationic surfactants was indicated by surface tension measurement, CMC determination, calculation of surface excess concentrations and area per molecule of individual surfactants and their mixtures. Molecular interactions of anionic and cationic surfactants in mixed monolayers and aggregates were calculated by using regular solution theory to find molecular interaction parameters β ^σ and β ^M . Morphologies of surfactant solutions were studied by cryogenic TEM. The use of binary mixtures of anionic/cationic surfactants significantly broadens the scope of application for conventional chemical EOR methods.     

CLAs制备及其稳定性的实验研究

制备了预分散溶剂萃取所需的胶质液泡(CLAs),探讨了溶质的存在对CLAs稳定性的影响. 结果发现,在表面活性剂浓度相同时[离子型表面活性剂浓度为1 g/L,非离子型表面活性剂浓度为1.0%(j)],溶质(苯甲酸)的存在对CLAs稳定性的影响很大,许多在没有溶质存在的条件下能够制备得到稳定的CLAs的表面活性剂组合,在加入了溶质后,不能再制备得到稳定的CLAs. 对于在溶质存在的条件下仍能制备得到稳定的CLAs的表面活性剂组合,考察了表面活性剂浓度对所制得的CLAs平均直径的影响. 结果发现,随着离子型表面活性剂和非离子型表面活性剂浓度的增大,CLAs平均直径逐渐减小. 另外,考察了离子型表面活性剂的类型对CLAs稳定性的影响. 结果发现,当表面活性剂浓度相同时[离子型表面活性剂浓度为1 g/L,非离子型表面活性剂浓度为1.0%(φ)],阴离子表面活性剂十二烷基硫酸钠和十二烷基苯磺酸钠可制备得到稳定的CLAs,而阳离子表面活性剂十六烷基三甲基溴化铵不能制备得到稳定的CLAs.     

Effects of three surfactant types of anionic, cationic and non-ionic on tensile properties and fracture surface morphology of epoxy/MWCNT nanocomposites

Three types of surfactants were used to enhance the dispersion of multi-wall carbon nanotubes (MWCNTs) in the epoxy matrix. MWCNTs were separately treated with non-ionic (polyoxyethylene octyl phenyl ether, Triton X-100), cationic (hexadecyl-trimethyl-ammonium bromide, CTAB) and anionic (sodium dodecyl sulfate, SDS) surfactants and their effects were evaluated on the dispersion state and surface chemistry, as well as on the tensile properties and tensile fracture surface morphology of MWCNTs/epoxy nanocomposites. The active surfaces of the carbon nanotubes were characterized by FTIR. The non-ionic surfactant, Triton X-100, had the best effect on dispersion of the MWCNT in the epoxy matrix, thus, positively affecting the tensile parameters of the corresponding nanocomposites which were attributed to the ??bridging?? effects between the MWCNT and epoxy, introduced by the hydrophobic and hydrophilic heads of the corresponding surfactant. Presence of MWCNTs as reinforcing agent increased the elastic modulus of nanocomposites, indicating the improved interfacial adhesion between CNTs and polymer matrix. The regions of nucleation and propagation of cracks were clearly seen in the SEM micrographs of the tensile fracture surface of the nanocomposites. The cracks deviated on reaching the carbon nanotubes. The dispersing aiding capabilities of the three surfactants used in the present study were as follows: cationic?<?anionic?<?non-ionic.     

Effect of alkyl groups in anionic surfactants on solution properties of anionic-nonionic surfactant system

The effect of different alkyl chains of anionic surfactants on properties of binary anionic-nonionic mixed surfactant systems was studied. These systems included ocytldodecyl-, and cetylsulfoacetates mixed with isooctyl phenol nonyl ethoxylate. The critical micelle concentration of mixed surfactants shifted to lower values compared to those of the single anionic surfactants. Effectiveness values increased with decreases in the mole fraction of anionic surfactants. The negative values of interaction parameter (β) increased with increases in the chain length of anionic surfactants.     

单分散二氧化硅超细颗粒的制备

利用3种不同类型的表面活性剂反胶团体系制备SiO2超细颗粒,并与传统的Stober制备方法进行了对比. 在阴离子表面活性剂AOT和非离子表面活性剂TritonX-100两类体系中,得到了单分散的SiO2超细颗粒．在AOT体系中颗粒粒径随体系水含量w。的增大而增大;而TritonX-100体系中,颗粒粒径随w。的增大而减小;在阳离子表面活性剂(如CTAB,TOMAC)体系中无法得到SiO2超细颗粒．对不同体系所得颗粒的粒径标准偏差及粒度分布进行了对比,结果表明制备粒径小于100 nm的SiO2颗粒,反胶团法明显优于Stober方法,粒径相对标准偏差较低, 而对粒径大于100 nm的颗粒,Stober方法仍不失为一种很好的制备途径．     

The stabilization effect of mixed-surfactants in the emulsion polymerization of methyl methacrylate

Summary The emulsion polymerization of methyl methacrylate (MMA) was conducted at 50°C using either anionic or nonionic surfactants, or a mixture of the two at different surfactant concentrations. In the singlesurfactant systems a proportional relationship was observed between the total particle surface area per cm³ of aqueous solution at 90% conversion (TS) and the amount of surfactant used. For mixed-surfactant systems, a relationship close to an additive one was found between the TS value and the amount of each surfactant used. The particle number did not remain constant during the polymerization, while the TS value continuously increased. It was also found that MMA formed a paste easily at higher (M/W) ratios, which could be alleviated by using higher surfactant concentrations.