水性乳液/聚氨酯模型缔合增稠剂的触变性机理

以异佛尔酮二异氰酸酯(IPDI)与聚乙二醇(PEG, 分子量为4000, 6000和8000)为原料, 以直链醇(C12, C14, C16和C18)为封端剂, 合成了疏水改性乙氧基化氨基甲酸酯(HEUR), 并将其应用于乳液增稠. 采用核磁共振波谱(¹H NMR)、 傅里叶变换红外光谱(FTIR)及凝胶渗透色谱(GPC)表征了HEUR的结构、 分子量及其分布, 研究了其在水性乳液中的流变行为. 研究结果表明, 当HEUR封端基团为C14, C16和C18, 且质量分数增加到1.0%以上时, 增稠的乳液(Latex/HEUR)的流变曲线出现触变环, 为触变性流体. 当HEUR亲疏水比值(R_h)减小时, 疏水性增强, 触变环向低剪切速率( \dot{\gamma } )方向移动, 黏度下降率(Δη)增大; 当HEUR用量增加时, 触变环面积(S_loop)也增大. 这些触变性特点归因于HEUR在乳液中的缔合作用、 氢键作用及链缠结. 利用扫描电子显微镜(SEM)和原子力显微镜(AFM)对Latex/HEUR的聚集态和表面形貌进行了表征. 结果表明, 随着HEUR封端基团链长增加, Latex/HEUR颗粒粒径增大, 表面变粗糙.     

Rheological Behavior of Aqueous Solutions of Cationic Guar in Presence of Oppositely Charged Surfactant

The cationic guar (CG) is synthesized and the rheological behavior of aqueous solutions of CG in the presence of sodium dodecyl sulfate (SDS) is studied in detail. The steady viscosity measurements show that the zero shear viscosity enhancement can be almost 3 orders of magnitude as the concentration of SDS increases from 0 to 0.043%. The gel-like formation is observed as the concentration of SDS is greater than 0.016%. The oscillatory rheological measurements of CG solutions in the presence of SDS show that the crossover modulus is almost independent of the concentration of SDS whereas the apparent relaxation time increases swiftly upon increasing the concentration of SDS. The experimental results indicate that the strength rather than the number of the cross-links is greatly affected bySDS molecules. The mechanism concerning the effect of SDS upon the rheology of CG solutions can be coined by the two-stage model. Before the formation of cross-links at the critical concentration, the electrostatic interaction between SDS and cationic site of CG chains plays a key role and the SDS molecules bind to CG chains through the electrostatic interaction. After the formation of cross-links at the concentration greater than the critical concentration, the cooperative hydrophobic interaction become dominant and SDS molecules bind to the cross-links through the hydrophobic interaction. The rheological behavior of aqueous solutions of CG in the presence of SDS is chiefly determined by the micelle-like cross-links between CG chains. In fact, the flow activation energy of CG solution, obtained from the temperature dependence of the apparent relaxation time, falls in the range of transferring a hydrophobic tail of SDS from the micelle to an aqueous environment.     

Phase behavior and rheological properties of enzymatically synthesized trehalose decanoate aqueous solutions

Surface tension properties of an enzymatically synthesized equimolar mixture of trehalose mono- and didecanoate in aqueous solutions have been determined. At 20 degrees C a critical micellar concentration (CMC) of 50 micromol/l and a minimal surface tension of 28 mN/m have been obtained. Above the CMC, it has been shown that up to a concentration of 42 wt%, and in a 20-60 degrees C temperature range the sugar ester aqueous solutions do not form any crystalline structure, nor present any phase transition, and the trehalose decanoate molecules form an isotropic worm-like micellar phase. The rheological properties indicate however a more complicated picture in the same concentration and temperature ranges. In steady shear, the viscosity of the trehalose decanoate solutions do not exhibit any shear rate dependence from 1 to 100 s(-1) for concentrations up to 42 wt%. Below 0.8 wt%, the viscosity remains constant and close to that of water; then, between 0.8 and 23 wt%, the viscosity shows a quadratic increase with surfactant concentration. For higher concentrations, up to 42 wt%, no further significant increase in viscosity is observed. In oscillatory shear experiments, the solutions exhibit viscoelastic properties. The observed rheological behavior as a function of concentration and temperature may be due to a progressive evolution of the trehalose decanoate molecular associations: as the concentration increases, the system evolves towards an entangled and/or partially branched or cross-linked micellar network, and eventually a multiconnected network of cross-linked micelles.     

Thickening properties and emulsification mechanisms of new derivatives of polysaccharide in aqueous solution 2. The effect of the substitution ratio of hydrophobic/hydrophilic moieties

The thickening properties and association behavior of aqueous solutions of HHM-HEC (hydrophobically-hydrophilically modified hydroxyethyl cellulose) with various hydrophobic and hydrophilic substitution degrees were investigated. The HHM-HEC was used as an oil-in-water emulsifier and stable compositional regions were investigated as a function of polymer concentration and substitution degree. The viscosity of aqueous solutions of HHM-HEC increased drastically at lower concentration for HHM-HEC with a higher hydrophobic/hydrophilic substitution ratio. The intensity ratio of the first and third vibrational bands of pyrene (I(1)/I(3)) decreased with the increase of HHM-HEC concentration and the I(1)/I(3) reached a lower plateau at a lower concentration for HHM-HEC with a higher hydrophobic/hydrophilic substitution ratio. The concentration ranges of HHM-HEC solutions which stabilize O/W emulsions differ by the hydrophobic/hydrophilic substitution ratio. However the viscosity ranges of these HHM-HEC solutions were almost the same regardless of the hydrophobic/hydrophilic substitution ratio. At the suitable concentration range for emulsification, HHM-HEC networks have two properties: (1) oil particle retention capacity and (2) laxation which can trap emulsified particles.     

疏水缔合效应对聚丙烯酰胺类水溶液结构和流变性质的影响

以聚合物驱油为背景,研究了部分水解聚丙烯酰胺(HPAM)和缔合型部分水解聚丙烯酰胺(AHPAM)水溶液的结构与流变性质的差别.通过粘度法和静态激光光散射法得到了所分析的聚丙烯酰胺的分子量,用动态激光光散射法和粘度法分析了特定AHPAM分子缔合形态,并用流变学法测定了AHPAM在地层温度与矿化度条件下的线性粘弹性与非线性流变特性.着重讨论了临界缔合浓度的概念,研究了结构和流变性质的关系,以及分析了缔合对聚合物驱油的可能影响.实验结果表明,AHPAM水溶液在宽浓度范围存在分子缔合;一般临界缔合浓度的概念实际反映在进入亚浓溶液范围分子间缔合的效应,剪切速率约为10 s-1时,剪切粘度突降数倍,反映缔合结构在剪切场中的变化,该现象在高缠结浓度下较不明显;拉伸粘度随拉伸速率变化与HPAM定性不同,该拉伸特性反映了疏水缔合近程作用的本质.     

The effect of polymeric surfactants on the rheological properties of nanoemulsions

We have investigated the rheological properties of submicron emulsions and how they are affected by the structure of polymeric surfactants. We have prepared oil-in-water emulsions stabilized with five steric surfactants, two of them belonging to the Myrj family and three belonging to the Pluronic family, with key differences on their structures. Droplet size and volume fraction have been kept constant to analyze only the influence of the surfactant. The viscoelasticity has been characterized by dynamic oscillatory shear experiments, while the shear viscosity was measured during steady shear flow tests. The results show a qualitatively similar gel-like behavior for all the emulsions, but with remarkable quantitative differences. Surfactants with longer hydrophilic tails produced emulsions with higher viscoelasticity. Pluronics, having a central hydrophobic part between two hydrophilic tails, produced emulsions with notably higher viscoelasticity and yield stress than Myrjs with comparable hydrophilic tails. The reason for this seems to be a more efficient steric barrier at the interface, induced by this central hydrophobic part.     

Celluloses in an ionic liquid: the rheological properties of the solutions spanning the dilute and semidilute regimes

The ionic liquid of 1-allyl-3-methylimidazolium chloride ([amim]Cl) was used as the good solvent to dissolve celluloses. Cellulose concentration covers the range of 0.1-3.0 wt %, spanning both the dilute and semidilute regimes. The rheological properties of the cellulose ionic liquid solutions have been investigated by steady shear and oscillatory shear measurements in this study. In the steady shear measurements, all the cellulose solutions show a shear thinning behavior at high shear rates; however, the dilute cellulose solutions show another shear thinning region at low shear rates, which may reflect the characteristics of the [amim]Cl solvent. In the oscillatory shear measurements, for the dilute regime, the reduced dimensionless moduli are obtained by extrapolation of the viscoelastic measurements for the dilute solutions to infinite dilution. The frequency dependences of the reduced dimensionless moduli are intermediate between the predictions from the Zimm model and elongated rodlike model theories, while the fitting by using a hybrid model combining these two model theories agrees well with the experimental results. For the semidilute regime, the frequency dependences of moduli change from the Zimm-like behavior to the Rouse-like behavior with increasing cellulose concentration. In the studied concentration range, the effects of molecular weight and temperature on solution viscoelasticities and the relationship between steady shear viscosity and dynamic shear viscosity are presented. Results show that the solution viscoelasticity greatly depends on the molecular weight of cellulose; the empirical time-temperature superposition principle holds true at the experimental temperatures, while the Cox-Merz rule fails for the solutions investigated in this study.     

Analysis of interfacial phenomena of aqueous solutions of polyethylene oxide and polyethylene glycol flowing in hydrophilic and hydrophobic capillary viscometers

Viscosities of aqueous solutions of five polyethylene oxide (PEO) samples with molar masses from 1.5 x 10(5) to 1.0 x 10(6) were carefully measured in a polytetrafluoroethylene (PTFE) capillary Ubbelohde viscometer in the concentration range from dilute down to extremely dilute concentration regions and compared with those of the same sample obtained from a glass capillary viscometer. At the same time, viscosities of aqueous solutions of three PEG samples in glass and paraffin-coated capillary viscosity were measured. The wall effects occurred in viscosity measurements for PEO and PEG aqueous solutions in different capillary viscometers were theoretically analyzed and discussed. It was found that different interfacial behaviors occurred in both hydrophobic and hydrophilic capillary viscometers respectively and the interfacial behaviors also exhibit molar mass dependence.     

Rheological properties of hexadecyl dimethyl amine modified carboxymethyl hydroxyethyl cellulose solutions and its gelling process

To obtain a new fracturing fluid viscosifier, hexadecyl dimethyl amine was used to modify carboxymethyl hydroxyethyl cellulose (CMHEC) to obtain a product called HD-CMHEC with high viscosity. The rheological properties of HD-CMHEC solutions and CMHEC solutions were studied. For the concentration of 0.3%, the viscosity of CMHEC and HD-CMHEC solutions is, respectively, 19.0?mPa?·?s and 73.6?mPa?·?s, respectively. The viscosity of HD-CMHEC solution increases 2.8 times than before. The thixotropy and viscoelasticity of HD-CMHEC solutions become stronger. As a typical viscoelastic fluid, HD-CMHEC solutions show better rheological performance than that of CMHEC solutions. The gelling process of HD-CMHEC solutions under steady shear was studied in detail. The concentrations of HD-CMHEC solutions, shear rates, and crosslinking agent were investigated. Viscosity versus time curves during the crosslinking process were obtained. The four-parameter crosslinking rheokinetics equation can describe the gelling process of HD-CMHEC solutions under different conditions well. Study on the gelling process of HD-CMHEC solutions under steady shear contributes to the understanding of gel formation, and provides theoretical guidance for exploration and exploitation of the system.     

铝/镁混合金属氢氧化物正电胶体粒子体系的触变性

采用恒定低剪切速率方法和动态实验方法研究了铝/镁混合金属氢氧化物(MMH)悬浮体的流变性,着重考察了剪切历史和恢复时间等因素对悬浮体触变性的影响,发现MMH粒子深度的增加使得悬浮体从粘性流体变为“类固体”;恒定低剪切速率方法和动态实验方法研究悬浮体的结构恢复过程给出了不同的结果,唯象地解释了MMH悬浮体触变性产生的原因,认为触变性结构是由于粒子间的静电排斥作用而形成的,与粘土悬浮体相比,两者的流变性具有诸多相似之处,只是所带电荷符号相反。     

Rheological properties of a telechelic associative polymer in the presence of alpha- and methylated beta-cyclodextrins

The viscosity of hydrophobic ethoxylated urethane (HEUR) solution decreased in the presence of alpha-CD or m-beta-CD; however their interactions were quite different. When the alpha-CD/hydrophobe molar ratio exceeded 5.0, the viscosity was close to that of a PEO solution of similar molecular weight. Oscillatory shear indicated that the mechanically active chains in HEUR solution decreased with the addition of alpha-CD. This agreed with the hypothesis that alpha-CD formed an inclusion complex with the hydrophobic moiety of the HEUR polymer, thereby destroying the transient hydrophobic associative network. The viscosity/temperature relationship of the alpha-CD/HEUR system (for HEUR with 70% of the PEO chains capped at both ends) did not obey the Arrhenius relationship for alpha-CD/hydrophobe molar ratio in the range 0.8-5.0. The low shear viscosity increased with increasing temperature at molar ratio of 1.0, and this was attributed to the competitive complexation of the alpha-CD/hydrophobe and the alpha-CD/PEO chain. Increasing temperature favored alpha-CD/PEO complexation. Comparison between the behavior of alpha-CD/HEUR and m-beta-CD/HEUR resulting from the different binding characteristics was discussed.     

丙烯酰胺型阴离子表面活性单体与丙烯酰胺共聚物水溶液的流变特性

以丙烯酰胺型阴离子表面活性单体2-丙烯酰胺基十四烷基磺酸钠(NaAMC14S)为共单体,与丙烯酰胺(AM)的水溶液均相共聚合,使NaAMC14S的浓度分别处于临界胶束浓度上下,分别制备了具有无规结构与微嵌段结构的两类共聚物;用红外光谱法对共聚物的结构进行了表征,使用乌氏粘度法测定了特性粘数,相对表示出了共聚物的分子量;采用荧光探针法与表观粘度法重点研究了两类共聚物的疏水缔合性与水溶液的流变特性.研究结果表明,具有微嵌段结构的共聚物具有很强的疏水缔合性,当其水溶液的浓度达0.2wt%后,表观粘度迅速提高;其水溶液的切力变稀行为具有明显的可逆性,表现出强的抗剪切性能.本研究中特别发现,具有微嵌段结构的共聚物其盐水溶液的表观粘度远高于纯水溶液的表观粘度,当共聚物浓度为0.3wt%、CaCl2浓度为2wt%时,溶液的表观粘度竟然提高了3个数量级,表现出独特的正性盐敏性(即遇盐变稠).     

Effect of Thermal History on Rheological Properties of Partially Hydrolyzed Polyacrylamide／Anionic Surfactant SDS Complex Systems

The effects of thermal history on the rheological properties of partially hydrolyzed polyacrylamide/sodium dodecyl sulfate complex aqueous solutions have been studied using both steady shear and dynamic temperature sweep characterizations. An abnormal rheological behavior was found that dynamic moduli of the aqueous solutions increased, while the viscosity decreased after thermal treatment,which could help to gain insight into the micro-phase evolution of the polymer/surfactant complex aqueous solutions and its dependence on temperature     

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.     

聚丙烯酰胺类疏水缔合物的增黏因素研究

合成了6种不同修饰度的聚丙烯酰胺疏水聚合物(PAM1~PAM6), 考察了聚合度、 共聚物片段含量及疏水基团大小等内部因素和聚合物的抗剪切能力、 剪切恢复性及抗盐性等外部因素对这些疏水聚合物分子间、 分子内缔合的影响规律.     

十二烷基聚氧乙烯硫酸钠胶束体系的流变性质研究

用流变学方法研究了无机电解质KBr存在时,阴离子表面活性剂十二烷基聚氧乙烯(3)硫酸钠(SDES)水溶液中胶束的生长和结构。通过测量体系的稳态剪切粘度(η)和应力(σ)关系,得到零剪切粘度(η0)、复合粘度(|η^*|)、动态模量[储能模量(G')和损耗模量(G")、平台模量(G0)、结构松驰时间(τ)等流变学参数,并应用Cox-Merz规则和Cole-Cole图,发现在SDES/KBr体系中可以形成蠕虫状胶束网络结构,体系为假塑性流体,偏离Maxwell模型,具有非线性粘弹性,没有单一的结构松驰时间。     

Temperature effect of hydrophobically modified polyethylene oxide at the air–water interface

Surface pressure (π)–area (A) isotherms of hydrophobically modified polyethylene oxide (HEUR) at the air–water interface was examined. Conformational transitions between pancake, mushroom, and brush states of the hydrophilic backbone influence the intermolecular interaction between the hydrophobic chains. We choose relatively long (18 carbons) hydrophobic ends, which have large hydrophobic interactions, and investigate the main chain effect by change in the length of the hydrophilic PEO chain. At high surface concentration region, the temperature coefficient of surface pressure, dπ/dT, was larger by increasing the portion of the hydrophobicity. This indicates an increase in surface energy and a decrease in surface enthalpy at high surface concentrations. As alkyl chains on both sides of HEURs are anchored at the air–water interface, restriction caused by the alkyl chain would be smaller for the long PEO chain, but the larger for the short PEO chain length.     

丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的粘度性能

通过改变丙烯酰胺 (AM)与苯乙烯 (St)两单体的投料比 ,在微乳液介质中制备了分子组成系列变化的丙烯酰胺 苯乙烯双亲嵌段共聚物 (PAM b PSt) ,使用旋转粘度计测定了共聚物水溶液的表观粘度 ,详细考察了共聚物浓度、共聚物链结构、剪切速率、盐度及温度等因素对共聚物水溶液表观粘度的影响规律 .研究结果表明 ,由于PAM b PSt分子链中的PSt疏水嵌段链段之间具有强的疏水缔合作用 ,导致其具有独特的流变性能 .当共聚物水溶液的浓度高于某一临界值后 ,疏水缔合作用以分子间的缔合为主 ,大分子链之间会形成动态物理交联网络 ,增大了流体力学体积 ,使PAM b PSt水溶液可产生良好的增稠性能 ;疏水缔合作用是一吸热过程 ,升高温度有利于分子间的缔合 ,因此PAM b PSt水溶液具有良好的耐温性 ;聚合物水溶液中盐类物质的存在 ,会增强溶剂的极性 ,有利于分子间的缔合 ,使PAM b PSt水溶液具有良好的耐盐性 .     

Rheology of viscoelastic solutions of cationic surfactant. Effect of added associating polymer

Rheological studies were performed with aqueous salt solutions of viscoelastic cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride (EHAC) and its mixtures with hydrophobically modified polyacrylamide. The solutions of surfactant itself above the concentration of crossover of wormlike micelles exhibit two regions of rheological response. In the first region, they behave like polymer solutions in semidilute regime characterized by viscoelastic behavior with a spectrum of relaxation times. In the second region, unlike polymer solutions their relaxation after shear is dominated by a single relaxation time. Being composed of "living" micelles, the EHAC solutions easily lose their viscosity at the variation of the external conditions. For instance, heating from 20 to 60 degrees C reduces viscosity by up to 2 orders of magnitude, while added hydrocarbons induce a sudden drop of viscosity by 3-6 orders of magnitude. Polymer profoundly affects the rheological properties of EHAC solutions. The polymer/surfactant system demonstrates a 10,000-fold increase in viscosity as compared to pure-component solutions, the effect being more pronounced for polymer with less blocky distribution of hydrophobic units. A synergistic enhancement of viscosity was attributed to the formation of common network, in which some subchains are made up of elongated surfactant micelles, while others are composed of polymer. At cross-links the hydrophobic side groups of polymer anchor EHAC micelles. In contrast to surfactant itself, the polymer/surfactant system retains high viscosity at elevated temperature; at the same time it keeps a high responsiveness to hydrocarbon medium inherent to EHAC.     

Rheological properties of polyurethane adhesives containing silica as filler: influence of the nature and surface chemistry of silica

Four silicas, two fumed silicas (one hydrophilic and one hydrophobic) and two precipitated silicas (one hydrophilic and one hydrophobic), were added as filler to solvent‐based polyurethane (PU) adhesive formulations. In general, the addition of silica increased the viscosity, the storage and loss moduli of the PU adhesives but only the hydrophilic fumed silica exhibited pseudoplasticity and thixotropy. The rheological properties imparted by adding filmed silicas to PU adhesive solutions were more noticeable than that of precipitated silicas. Interactions between the hydrophilic fumed silica, the polyurethane and/or the solvent seemed to be responsible for the improved rheological properties of filled PU adhesives.