A novel associative latex thickener using ethoxylated behenyl methacrylate as functional monomer

<正>Alkali-soluble associative latex thickeners modified with hydrophobic long chain alkyl groups were prepared using common acrylics and varying amount of a functional monomer,ethoxylated behenyl methacrylate(BEM),through emulsion polymerization.It was found that the size of the emulsion particle became larger with addition of BEM.The light transmittance of the thickener latex sharply increased with pH varied from 6 to 7.The associative latex thickener manifested a higher viscosity when solids in the latex thickeners were kept at 0.5 wt%or higher,and the optimal amount of BEM was found to be around 2.5 wt%,or 0.16 mol%.All thickener latexes modified with BEM have better shearing resistance than the BEM-free thickener.     

含三苯基乙基苯氧基聚氧乙烯醚甲基丙烯酸酯功能单体的缔合型乳液增稠剂的制备及增稠机理

采用半连续法乳液聚合以甲基丙烯酸、丙烯酸乙酯、邻苯二甲酸二烯丙酯和不同量的功能单体三苯基乙基苯氧基聚氧乙烯醚甲基丙烯酸酯(SEM-25)为原料合成了疏水改性碱溶性增稠剂乳液. 测定了增稠剂乳液的粘度、透光率、pH、粒径及其分布, 结果表明随着pH值的增加, 乳液的粘度和透光率首先迅速升高, 然后缓慢下降. 随着SEM-25用量的增加, 乳胶粒的粒径先增大后减小. 与不含SEM-25的乳液增稠剂相比较, SEM-25低含量增稠剂的增稠效果和抗剪切性没有提高, 只有当SEM-25用量提高至单体质量的12%, 且乳液固含量大于0.65%时, 所制备缔合型增稠剂乳液的粘度和流变性比不含SEM-25的增稠剂才有明显提高. 在此基础上研究了增稠剂对苯丙乳液的增稠性. 含有增稠剂的苯丙乳液的粘度和透光率随pH值的变化与纯增稠剂乳液的变化类似. 只有当加入0.34 wt%苯丙乳液固体质量的增稠剂, 并且增稠剂中SEM-25含量达到5 wt%时苯丙乳液的粘度与使用不含SEM-25的增稠剂增稠的粘度相比才有明显增高. 在此基础上对增稠剂的增稠机理进行了探讨.     

交联剂含量对憎水改性缔合型增稠剂性能的影响

以甲基丙烯酸、丙烯酸乙酯和功能单体二十二烷基聚氧乙烯醚甲基丙烯酸酯为原料,过硫酸铵为引发剂,变化交联剂邻苯二甲酸二烯丙酯(DAP)的量,采用半连续乳液聚合方法合成了DAP含量不同的憎水改性缔合型增稠剂乳液.测定了乳液的黏度和乳胶粒粒径及其分布等性能.考察了乳液运动黏度和透光率随pH的变化.随着pH值的增加,乳液的透光率...     

Surfactant and Electrolyte Effects on Latex Depletion Flocculation by Thickeners

Summary: Polymer thickeners can induce good dispersion, bridging, or depletion flocculation of latexes depending on the polymer structure and concentration. Unlike non-associative polymers, associative polymers have the ability to create a good latex dispersion. However, when the associative interactions are destroyed, depletion flocculation of the latex can result. This happens when an excess of ionic surfactant is added to the system. In addition, the surfactant may associate with the thickener backbone, thus modifying the molecular volume of the polymer thickener. This paper explores the effect of anionic surfactant and electrolyte on the molecular volume of both associative and non-associative thickeners. Both HEUR and HASE structures are included. For HEUR thickeners, formation of a pseudo-polyelectrolyte through the association of anionic surfactant with the polyethylene oxide backbone is confirmed. Further, the ability of the thickener to depletion flocculate latexes as a function of surfactant and electrolyte is explored. Experimental critical flocculation concentrations (CFC) are compared to values expected based on molecular volume and potential energy calculations. A good correlation is found between molecular volume and CFC for a wide range of thickener compositions.     

水煤浆添加剂与煤之间的相互作用规律研究 Ⅰ. 复合煤颗粒间的相互作用对水煤浆流变性的影响

使用12种不同分散剂对14种不同变质程度的煤进行了成浆性实验，分析了182个水煤浆(CWS)样品的流变性。结果表明，低变质程度和高灰煤浆多呈屈服假塑性，煤的性质起主导作用；变质程度高且灰分较低煤浆的流变性，主要依赖于分散剂的结构与性质；分子结构单元立体空间效应大，疏水基团与亲水基团呈立体间隔分布的分散剂，易形成屈服假塑性CWS；分子线度长，亲水基团与疏水基团呈线性间隔分布的分散剂，易形成胀塑性CWS。复合煤粒间的相互作用方式是决定CWS流变特性的关键。     

含二十二烷基聚氧乙烯醚甲基丙烯酸酯功能单体的缔合型乳液增稠剂的制备及表征

以甲基丙烯酸、丙烯酸乙酯、邻苯二甲酸二烯丙酯和不同量的功能单体二十二烷基聚氧乙烯醚甲基丙烯酸酯(BEM)为原料,采用半连续乳液聚合方法合成了疏水改性碱溶性缔合型增稠剂乳液.测定了增稠剂乳液的粘度、透光率、乳胶粒粒径及其分布等性能,考察了不同固含量下乳液粘度和透光率随pH的变化情况.结果表明随着BEM用量的增加,乳胶粒粒径逐渐增大.随着pH值的增加,乳液的粘度首先迅速升高,然后缓慢下降.与不含BEM的增稠剂乳液相比,当乳液固含量大于0.5%,BEM含量占单体量低于5.0wt%时,该缔合型增稠剂的增稠效果和抗剪切性有显著提高,BEM含量较高(8.0wt%或更高)时反而使增稠效果和抗剪切性变差.在此基础上研究了增稠剂对苯丙乳液的增稠效应,结果显示BEM含量占单体量的2.5wt%时,对苯丙乳液的增稠作用最好.与使用功能单体三苯乙基苯酚聚氧乙烯醚甲基丙烯酸酯改性的增稠剂相比,含BEM的增稠剂在BEM用量较少的情况下就能起到明显的增稠效果.     

Influence of prepolymers molecular weight on the viscoelastic properties of aqueous HEUR solutions

A series of hydrophobically modified ethoxylated urethanes (HEURs) were synthesized by a step growth polymerization of polyethylene glycol with dicyclohexylmethane diisocyanate (H12MDI). The thickeners were produced with different sizes of the hydrophilic section by changing the molar ratios of reactants. The size of the hydrophobic ends was constant for all prepared samples. The changes in hydrophilic lengths were correlated with the rheological properties of HEURs aqueous solutions. The intrinsic viscosity measurements showed that associates are present even at very low concentration. The response of these HEUR systems in aqueous solution to both steady shear and oscillatory shear was determined as a function of hydrophilic chain length and polymer concentration. Dramatic increases in viscosity are observed with decreasing molecular weight of the prepolymer (with a decrease of the hydrophilic components' size and at the same time an increased ratio between hydrophobic and hydrophilic sections of HEURs). Also, a steep increase in viscosity with increasing thickener concentration is obtained. The rheological properties of aqueous solutions of HEUR polymers can be described using a simple Maxwell model with a single relaxation. The dynamic measurements verified the results obtained from the steady state measurements about the hydrophilic section size and its effect on the association phenomenon.     

Dispersion of TiN in aqueous media

The dispersion of TiN powders in aqueous media was studied through XPS, zeta potential, adsorption, sedimentation, and rheology measurements. XPS showed that there are TiO2, TiN, and TiOxNy sites on the TiN particle surface. In the absence of dispersant, the isoelectric point (pH(IEP)) of the TiN particles was at pH 2.2. Based on the surface properties of TiN particles, a cationic polymer, polyethylene imine (PEI), was selected as a dispersant. In the presence of PEI, the pH(IEP) shifted from pH 2.2 to pH 11.10. It was evidenced that TiN slurries could be stabilized around pH 9.50 with 1-2 wt% PEI as dispersant. Subsequently, TiN slurries with solid content as high as 57 vol% were developed and exhibited dilatant rheological behavior at high shear rate. The results showed that PEI is an effective dispersant for TiN in aqueous media.     

Rheological properties of hydrophobically modified alkali-soluble polymers—effects of ethylene–oxide chain length

The rheological properties of hydrophobic alkali-soluble associative polymers (HASE) were studied using controlled rate (Mettler LS40) and controlled stress (TA CSL 500) rheometers. The effects of pH and polymer concentrations on the rheological properties of three HASE model polymer systems (i.e., HASE 5141, 5134, and 5142, with a degree of ethoxylation of 2.5, 10, and 40 mol, respectively) and a reference polymer without associative hydrophobes (MAAEA) were examined. As the pH is increased by addition of ammonia to greater than 5–6, the carboxyl groups ionize to carboxylate ions and the polymers become water soluble. The HASE polymers thicken mainly by hydrophobic association. Viscosity can increase by two to three orders of magnitude as pH is raised to 9. The degree of ethoxylation in the macromonomer controls the nature of the hydrophobic association junctions by altering the flexibility and hydrophobicity of the macromonomer. Optimum thickening efficiency is observed in the system with approximately 10 mol of an ethylene–oxide spacer between the polymer backbone and the macromonomer. Viscoelastic study shows that the maximum thickening efficiency also corresponds to the dominant elastic property observed in the system with 10 mol of EO. All the model systems except the control system without hydrophobe exhibit strain thickening of the viscous and elastic components. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2275–2290, 1998     

Investigating the effect of hydrophobic structural parameters on the thickening properties of HEUR associative copolymers

Hydrophobically modified ethoxylated urethanes (HEUR) associative copolymers are prepared through the hydrophobic modification of polyethylene glycol based polyurethanes. These types of thickeners are categorized as anionic associative thickeners. To investigate the effect of structure of the hydrophobic groups on the thickening properties, three different hydrophobic groups were selected. These groups were comprised of cetyl alcohol (16 carbons), dodecyl alcohol (12 carbons) and a cyclic group such as cyclo hexanol. These functional groups were substituted on the identical prepolymers made from H₁₂MDI and polyethylene glycol. Here, three different urethane associative polymers containing hydrophobic segments and different hydrophobic groups were synthesized. The viscoelastic characteristics of all the samples were determined using a cone and plate rheometer. The viscosities of the examined HEUR samples showed both Newtonian and non-Newtonian behaviours (shear thinning and thickening) for the explored shear rates window. The steady shear viscosity results were interpreted using the theories by Raspaud [Macromolecules 27 (1994) 2956] and Semenov [Macromolecules 28 (1995) 1066]. The Cox-Merz rule happened to be applicable to these systems for the various hydrophobic ends and concentrations at lower shear rates indicating typical associative polymer behaviour. The cyclic end groups did not show viscoelasticity for the frequencies window explored. The zero shear viscosity increased by almost two orders of magnitude from HEUR-cyc to HEUR-dod and by four orders of magnitude from HEUR-cyc to HEUR-cet. The intermediate shear thickening was only observed for the concentrated HEUR-cet samples.     

Polyelectrolyte-surfactant association—from fundamentals to applications

Mixed polymer-surfactant systems have broad applications, ranging from detergents, paints, pharmaceutical, and cosmetic to biotechnological. A review of the underlying polymer-surfactant association in bulk is given. While ionic surfactants bind broadly to polymers, nonionics only do so if the polymer has a lower polarity and can interact by hydrophobic interactions. Water-soluble polymers, which have hydrophobic groups, form physical cross-links, hence they may be used as thickeners. The rheological behaviour is strongly influenced by various cosolutes; especially strong effects are due to surfactants and both a decrease and an increase in viscosity can occur. When the polymer-surfactant interactions are particularly strong, an associative phase separation can occur, like in the case where there is electrostatic attraction as well as hydrophobic; this and other types of phase separation phenomena are described. Except for linear ionic and nonionic polymers, the interactions between surfactants and cross-linked polymers, microgel particles and covalent macroscopic gels are analyzed, as well as the possibility of forming gel particles of interest for encapsulation purposes. Furthermore, the behavior of these mixed systems on surfaces is discussed. In particular, we consider the adsorption of mixtures of ionic polymers and oppositely charged surfactants on polar and nonpolar surfaces. Depending on concentration, an ionic surfactant can either induce additional polyion adsorption or induce desorption. Kinetic control of adsorption and, in particular, desorption is typical. Important consequences of this include an increased adsorption on rinsing and path dependent adsorbed layers. Recently, considerable attention has been given to the interaction between DNA and cationic surfactant, both as a means to understand the behaviour of DNA in biological systems and to develop novel formulations, for example for gene therapy. Here we review aspects such as DNA compaction, DNA covalent gels and DNA soft nanoparticles.     

Synthesis and characterization of monodisperse magnetic composite particles for magnetorheological fluid materials

Monodisperse magnetic composite particles (MCP) were prepared and characterized for a study of magnetic field-responsive fluids. Magnetic composite particles used are iron oxide-coated polymer composite particles, which were synthesized through in situ coating of iron oxide onto pre-existing polymer particles by the reduction of ferrous fluids. For a uniform and bulk coating of iron oxide, the porous structure was introduced into the substrate polymer particles through a two-step seeded polymerization method. Moreover, surface cyano-functionality was born from acrylonitrile unit of substrate polymer and it played an important role in obtaining successful uniform coating. The structure of the composite particle was analyzed by using a thermo gravimetric analysis (TGA) and a X-ray diffraction (XRD) analysis. The magnetization property of the particle was also observed. Then, the rheological properties of monodisperse magnetorheological (MR) suspensions of magnetic composite particles were examined under a magnetic field using a parallel-plate type commercial rheometer. From the rheological measurements, it was found that MR properties of the magnetic composite suspensions are dependent on the iron oxide content and the fluid composition.     

Dispersion of Zirconia in the Presence of Dolapix PC75

The effect of Dolapix PC75 on the electrokinetic and rheological behavior of nano zirconia particles is presented here. The effect of pH, concentration of dispersant, and solids loading on zeta-potential and rheological behavior was studied. Upon interaction with the dispersant, the iso-electric point of zirconia changed and the surface became more negative with increasing concentration of dispersant, suggesting a strong interaction. Maximum charge was obtained in the presence of about 200 ppm of Dolapix. Rheological tests at pH 7 showed that the zirconia suspension is viscous at high solids loading and addition of the dispersant decreased the viscosity substantially especially at high solids loading (>50 wt%). Sedimentation tests confirmed that Dolapix PC75 is a good dispersant for zirconia particles at pH values of 7 and above.     

Effects of nonionic surfactant and associative thickener on the rheology of polyacrylamide in aqueous glycerol solutions

The effect of a low molecular weight nonionic surfactant and an acrylic associative thickener on the rheology of polyacrylamide in aqueous glycerol solutions under steady shear was experimentally investigated. The nonionic surfactant (Tween20), associative thickener (Acrysol TT935) and polyacrylamide (Separan AP30) underwent complex molecular interactions in solution as reflected by rheological measurements. The surfactant also interacted with the glycerol solvent. The addition of surfactant in aqueous glycerol solutions reduced the surface tension, as well as the solution viscosity, at low surfactant concentration. The solution viscosity went through a minimum at certain surfactant concentration, depending on the composition of glycerol/water mixture, before increasing again. Similar behavior was found when the surfactant was added to the polyacrylamide solution, except there was an initial increase in the viscosity before the reduction. The associative thickener, Acrysol TT935 (an anionic acrylic emulsion copolymer) exhibited a strong affinity with polyacrylamide in solution, as indicated by a sharp increase in the solution viscosity. The dilute polyacrylamide solution became highly elastic in the presence of either the nonionic surfactant on the associative thickener. A threestage model was proposed to describe the surfactant/thickener/polymer interactions.     

环糊精包合作用对疏水缔合聚合物流变调节与应用

近年来,利用超分子作用力调节体系流变行为备受人们关注,已在多领域中展现出广泛的应用前景。而环糊精包合作用是一类重要的超分子作用力,向缔合聚合物水溶液中加入环糊精,将拆散缔合结构,引起粘度和粘弹性急剧下降;竞争客体或酶的加入又会诱导分子间发生新的组装行为,使体系流变性得到恢复。本文综述了基于环糊精包合作用的分子组装与流变调节在理论及应用方面的研究现状,重点介绍了环糊精对不同缔合聚合物溶液的流变影响规律和外加物质对体系流变恢复的调节。     

Effect of associating polymer on the viscosity behavior of suspensions consisting of particles with different surface properties

Associating polymers which consist of water-soluble long-chain molecules containing a small fraction of hydrophobic groups (hydrophobes) behave as flocculants in aqueous suspensions. The effects of associating polymers on the rheological behavior are studied for single suspensions of particles with hydrophilic and hydrophobic surfaces, and their mixtures. For particles with hydrophilic surfaces, the suspensions are highly flocculated by a bridging mechanism, because the water-soluble chains adsorb onto hydrophilic surfaces. On the other hand, the particles with hydrophobic surfaces cannot be dispersed in water without polymer and the additions of a small amount of polymer are required for preparation of homogeneous suspensions. The associating polymer acts as a dispersant at low concentrations. However, further additions of polymer lead to a drastic increase in viscosity. Since the hydrophobes on one end of molecules adsorb onto hydrophobic surfaces and other hydrophobes tending from the particles can form micelles, the particles are connected by linkage of interchain associations. By mixing two suspensions of particles with hydrophilic and hydrophobic surfaces, the viscosity is substantially reduced and the flow becomes nearly Newtonian. The associating polymer in complex suspensions acts as a binder between the hydrophilic and hydrophobic surfaces. The hetero-flocculation which leads to the formation of composite particles may be responsible for the viscosity reduction of complex suspensions.     

Changes in the rheological and colloidal properties of paper coating liquids with paper-yellowing inhibition additives

This is an investigation of the effect of paper-yellowing inhibitors on the rheological, colloidal, and interfacial properties of paper-coating liquids and the associated changes in the liquid surface microstructure. In addition to rheological measurements, we measured the zeta potential and imaged the surface microstructure of coating liquids by transmission electron microscopy (TEM) using an advanced Pt/C replica technique. The zeta potential is related to the concentration of added inhibitors. The images reveal interparticle structuring with increasing concentration of inhibitors. The structuring is related to the interaction between the coating liquids and the inhibitors. It was also found that the viscosity and the elastic modulus increased with inhibitor concentration. The significant changes in mixture properties due to the additives show the importance of the rheological and surface characterization of liquids and the ensuing effect on the corresponding engineering process.     

Synthesis of hydrophobically modified poly(acrylamides) in water-in-oil emulsions

High-molecular-mass hydrophobically modified poly(acrylamides) have been prepared via water-in-oil miniemulsion copolymerization of acrylamide and lauryl methacrylate initiated by 2,2′-azoisobutyronitrile. The incorporation of the hydrophobic comonomer into the polymer backbone is indirectly confirmed by the rheological and associative properties of polymer solutions. The copolymers prepared from the reaction mixtures containing less than 5 mol % lauryl methacry late demonstrate the associative behavior in aqueous solutions, as evidenced by fluorescence spectroscopy (a decrease in the polarity parameter of pyrene), static and dynamic light scattering (overestimated effective molecular masses and appearance of a peak due to aggregates), and rheological measurements (a rise of viscosity relative to that of the acrylamide homopolymer). A further increase in the content of lauryl methacrylate leads to formation of polymers possessing limited solubility in water. At the acrylamide-to-hydrophobic monomer equimolar ratio, homopolymers arise along with the insoluble copolymer.     

Viscoelastic behaviour of butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid latices thickened with associative thickeners

The rheological behaviour of butyl acrylate/styrene/acrylic acid latices thickened with a hydrophobically modified ethoxylated polyurethane (HEUR) or hydrophobically modified alkali-soluble polyacrylate emulsion (HASE) was investigated. While the pseudoplastic character of frequency dependence of complex viscosity was similar for both thickeners, viscoelastic behaviour, expressed as the ratio of loss and storage moduli, significantly differed, indicating that the HEUR molecules, unlike swollen HASE particles, create a viscoelastic space structure. The increase in hydrophilicity of the particle surface, achieved by incorporation of 2-hydroxyethyl methacrylate (HEMA) monomer into the latex copolymer reduced the viscoelasticity of latices thickened with HEUR, but not of those thickened with HASE. This confirms that adsorption of hydrophobic end-groups on particle surface is important for thickening of latices with HEUR and that a physical network of latex particles interconnected by the thickener macromolecules is formed. To cite this article: O. Quadrat et al., C. R. Chimie 6 (2003).     

PAA/PEO comb polymer effects on rheological properties and inter-particle forces in aqueous silica suspensions

The effects of a poly(acrylic acid) (PAA)-poly(ethylene) (PEO) comb polymer dispersant on the rheological properties and inter-particle forces in aqueous silica suspensions have been studied under varying pH conditions. The comb polymer was found to adsorb more strongly under acidic than basic conditions, indicating that the PAA backbone of the copolymer preferentially adsorbs onto silica surfaces with the PEO "teeth" extending out from the surface into the solution. In the presence of low concentrations of copolymer, the silica suspensions were stable due to electrostatic repulsions between the silica surfaces. At higher copolymer concentrations and under neutral and basic conditions, where the copolymer interacted only weakly with silica, the suspensions showed a transition from a dispersed to weakly flocculated state and attractive forces were measured between silica surfaces. Under acidic conditions, the silica dispersion also destabilized at intermediate copolymer adsorbed density and then was re-stabilized at higher adsorbed coverage. The silica suspensions were stable at high copolymer coverage due to steric repulsions between the particles. The destabilization at intermediate coverage is thought to be due to polymer bridging between particles or possibly depletion forces.