Rheological Properties of Polymer-Containing Aqueous Aerosil Dispersions

The rheological properties of two- and three-component systems containing a solid phase (hydrated aerosil), water, and a water-soluble polymer were studied under static and dynamic conditions. Gels prepared by the cross-linking of these systems with CrCl₃were also investigated. Minimal concentrations of the polymer and the solid phase necessary for a gel-like system formation were determined. The kinetics of the gelation was studied. The formation process of the chemically cross-linked gels was found to be determined not only by the ratio between the concentrations of the solid phase, the cross-linking agent, and the polymer, but also by the degree of polymerization of the latter.     

Synthesis of LDHs and Rheological Properties of Laponite／LDHs Dispersions

The chemical composition, morphology of the particles of positively charged layered double hydroxides (LDHs) were studied by ICP, Mastersizer, TEM. The preliminary results indicated that with adding LDHs to 1% laponite dispersion the yield stress of laponite/LDHs mixed dispersions increased at first, then decreased dramatically to a minimum, and the yield stress rose again when LDHs increased further.     

聚合物多元醇分散体的流变特性

聚合物多元醇分散体(以下简称分散体)是接枝聚醚多元醇、聚醚多元醇和乙烯基单体聚合物的混合物,直接用于制备高回弹、高负载和阻燃的软质和半软质聚氨酯泡沫体,是新一代聚醚多元醇产品[1].分散体用于聚氨酯工业中各种产品的生产,除要求有良好的稳定性外,其最为重要的指标是粘度应小于3000mPa·s和乙烯基单体聚合物的含量(固含量)应大于40%.但分散体的粘度,随固含量的增加呈指数性增加[2].近年来,已有既具高固含量和良好稳定性,又有较低粘度的分散体的研究报道[3].本文在不同的反应条件下,合成了分散体,测定了其流变特性和体系中微粒的大小…     

添加剂对TiO2/水分散体流变性的影响

研究了TiO₂生产中有关助剂对其流变性能的影响,得到了TiO₂/水分散体的流变性能与三乙醇胺用量之间的关系,并找到了最佳用量.实验发现,六偏磷酸钠为分散剂时,其使用效果有时间依赖性;碳酸铵作絮凝剂时则对分散体的流变性能和形成的絮凝体有影响.     

Prediction of Rheological Properties of Multi-Component Dispersions by Using Artificial Neural Networks

This article shows the ability of artificial neural network (ANN) technology for predicting the correlation between rheological properties of multi-component food model systems and their chemical compositions. Multi-component food model systems were made of whey protein isolate (WPI) (2, 4 wt%), Iranian tragacanth gum (TG) (Astragalus gossypinus) (0.5, 1 wt%) and oleic acid (5, 10% v/v). The input parameters of the neural networks (NN) were these chemical compositions, namely WPI and TG concentrations, and oleic acid volume fractions. The output parameters of the NN models were rheological properties of multi-component food model systems (flow and consistency indices, viscosity, loss and storage moduli). Results showed that, ANN with training algorithm of back propagation (BP) was the best one for the creation of nonlinear mapping between input and output parameters. The best topology was 3-10-5. The ANN model predicted the rheological properties of multi-component food model systems with average RMSE 4.529 and average MAE 3.018. These results show that the ANN can potentially be used to estimate rheological parameters of multi-component food model systems from chemical composition. This development may have significant potential to improve product quality control and reduce time and costs by minimizing the rheological experiments.     

pH响应型P(HEMA/MAA)纳米微凝胶分散液的凝胶化行为和流变性能

制备了在修复受损组织方面有应用潜能的纳米级聚(甲基丙烯酸羟乙酯/甲基丙烯酸) (P(HEMA/MAA))微凝胶; 采用试管倒转法对不同pH值和浓度的P(HEMA/MAA)微凝胶分散液的凝胶化相转变行为进行了研究; 借助椎板流变仪考察了低浓度和高浓度微凝胶分散液的流变性能, 并对pH触发物理凝胶化相转变机理进行了推测. 结果表明: 在生理pH值环境下, 一定浓度的P(HEMA/MAA)微凝胶分散液可以发生凝胶化相转变形成凝胶态, pH=7时, HEMA/MAA进料摩尔比为8/2的微凝胶分散液凝胶化后得到的凝胶力学性能最佳, 最大弹性模量(G')可达7.58×10³ Pa; P(HEMA/MAA)微凝胶颗粒在不同条件下具有不同的溶胀效果, 导致低浓度分散液的表观粘度发生相应的变化, 并由此推测出微凝胶颗粒的溶胀过程由外及内, 分为三个阶段; 高浓度微凝胶分散液发生凝胶化相转变主要是由颗粒间或颗粒与分散介质间形成的空间静电稳定作用和氢键共同作用引起的.     

Rheological Properties of Silica Particle Suspensions in Mineral Oil

The rheological properties of particles suspended in a non‐polar mineral oil have been investigated as a function of volume fraction of particles, particle size, surface properties and shear rate. Three different types of particles were investigated; glass microspheres, monodisperse silica particles and fumed silica. The suspensions showed shear thinning behavior at higher volume fractions, and the viscosity increased with decreasing particle size. The hydrophobic particles display lass shear thinning effects. The relative viscosity of all the suspensions was well fitted to the Krieger and Dougherty model.     

Mg-Al-CO3水分散液的稳定性及流变性

水滑石;水分散体系;层状结构;Mg-Al-CO3水分散液的稳定性及流变性     

Rheological Behavior of Epoxy Resin Concentrated Dispersions

IntroductionWaterbornedispersionsofpolymerresinswithlow(orzero)contentofvolatileorganiccompoundshavereceivedmuchat'tentionowingtoincreasinglystrictenvironmentalandecologicalregulations.BisphenolAepoxyresinisacondensationpolymerofanextensivescopeofapplicationssuchasincomposites,coatings,adhesives.Therefore,thepreparationoftheepoxyresinwaterbornedispersionsisveryinteresting.Recently,wehavesuccessfullypreparedtheepoxyresinwaterbornedispersionswithhighsolidcontentbyphaseinversionemulsificationtec…     

Aqueous Dispersions of Positively Charged Al/Mg Mixed Metal-Hydroxide Particles:Surface Chemistry and Rheological Properties

The solids concentration, pH and NaCl were found to have a very significant effect on the rheological properties of aqueous dispersions of positively charged Al-Mg mixed metal hydroxide particles (Al-Mg MMH). At low solids concentrations the flow curves of the dispersions at natural pH followed the Newtonian model very well in the observed range of shear rate, while at high solids contents the dispersions developed a yielding type of response, with yield stress increasing rapidly as solids concentration increases. The variation in rheological properties with pH and NaCl contents correlated well with the change in surface properties of Al-Mg MMH particles. Al-Mg MMH dispersions with maximum yield stress occurred near the isoelectric point (IEP) where the Zeta potential (or electrophoretic mobility) is zero. At the IEP, the shear yield stress decreased monotonously in magnitude as a function of the increasing NaCl concentration, which is in contrast to the increment in the yield stress observed below the DEP at NaCl concentrations less than 0.1 mol dm^-3. At low NaCl concentrations, significant shear yield stress differences exist at and below the IEP. By contrast, at high NaCl concentrations, almost identical shear yield stress versus NaCl results are obtained in both cases.     

聚氨酯脲-丙烯酸酯水分散液的粒径及形态研究

研究了羧基含量、异氰酸酯指数（［ － ＮＣＯ］／［ － ＯＨ］） 、聚氨酯脲与聚丙烯酸酯组成比（ＰＵＵ／ＰＡ） 以及一系列制备工艺因素对聚氨酯脲—丙烯酸酯（ＰＵＡ） 水分散液粒子尺寸及形态的影响。结果表明：羧基含量和ＰＵＵ／ＰＡ 组成比增大或异氰酸酯指数减小都会导致分散液粒径减小;ＰＵＡ 中ＰＡ 含量越大,ＰＵＡ 水分散液粒子形态越不规整;工艺因素如搅拌强度、升温速率等对ＰＵＡ 水分散液粒子尺寸及形态的影响不符合传统乳液聚合的规律。     

Low-Shear Viscosities of Dilute Dispersions of Colloidal Rodlike Silica Particles in Cyclohexane

Low-shear viscosities have been studied for isotropic dispersions of uncharged colloidal silica rods in cyclohexane as a function of volume fraction Φ and aspect ratior_p. Intrinsic viscosities in the limit Φ → 0 agree with theoretical results [Brenner, H.,Int. J. Multiphase Flow1,195 (1974)] for colloidal cylinders. The Φ²term in the low-shear viscosity, accounting for two-particle interactions, is considerably larger than predicted by D. H. Berry and W. B. Russel [J. Fluid Mech.180,475 (1987)] for dilute hard-rod dispersions. The discrepancy is very likely due to weak interparticle attractions, which also account for the novel observation of an isotropic–isotropic phase separation in the silica rod dispersions. Our results demonstrate that, in comparison to spheres, high aspect ratios markedly increase both the shear viscosity and its sensitivity to even minor attractions.     

Mg-Al-CO3水分散液的稳定性及流变性

以n(Mg):n(AI)=3的层状双金属氢氧化物（LDH）作为研究对象,考察了其水分散液的稳定性及流变性。发现其水分散液的稳定性依赖于含固量及LDH的结构完整性。LDH水分散液的流变性与其特殊的层状结构密切相关,LDH水分散液具有剪切变稀作用且是可逆的,同时还具有触变性能。利用XRD表征LDH晶体结构,SEM及TEM考察了水分散液中LDH的晶粒形态。     

Rheological and Electrophysical Properties of Dispersions Based on Thermally Treated Magnetite and Aqueous Emulsions of Water-Soluble Polymers in Transformer Oil

Rheological, electrophysical, and sorption properties of magnetite dispersions modified with water-soluble polymers were studied as influenced by the temperature of heat treatment in the 300-600°C range.     

Adsorption of Oligomers from Dilute Solutions on the Surface of Ferromagnetic Fillers

The adsorption of oligomers from their dilute solutions on the surfaces of dispersed barium and strontium oxide ferrites and of neodymium-iron-boron alloy was studied. The main thermodynamic functions of the system components were evaluated. The features of their variation were established.     

Effect of Rotary Inertia on the Orientational Behavior of Dilute Brownian and Non-Brownian Fiber Suspensions

The orientational behavior of a dilute suspension of slender Brownian and non-Brownian fibers with rotary inertia in simple shear and turbulent channel flows is numerically investigated. The translational inertia of fibers is neglected. The equations describing the evolution of fibers orientation are integrated along the Lagrangian paths of the fluid elements. The fully developed turbulent channel flow at Re _τ = 180 is provided by a direct numerical simulation (DNS). The coupling between the flow field and the fiber dynamics is one way. The Brownian motion is modeled by a stochastic Wiener process. The results are compared with those of inertia-free particles. In simple shear flow, the inertial non-Brownian fibers align slower than the inertia-free fibers to the shear direction while they tend to the same steady state orientation. For Brownian fibers, the steady state orientation of inertial and inertia-free fibers differ. In turbulent channel flow, the second moment of the orientation distribution function shows an oscillatory behavior at high values of inertia for non-Brownian fibers while the oscillations disappear at lower inertia. For Brownian fibers, the oscillations are weaker due to the damping effect of the Brownian diffusivity.     

Colloidal Properties of Polychlorotrifluoroethylene-Based Multicomponent Dispersions

A polychlorotrifluoroethylene-based multicomponent dispersion in dimethylformamide (DMF) was used to prepare protective polymer coatings by the electrodeposition method. The properties of the fluoroplastic coatings were modified by the addition of a cationic polyelectrolyte and pigments of different natures to the dispersion, the pigments being codeposited on a cathode together with the fluoroplastic particles. The optimal composition of the dispersion was determined. It was found that all dispersion components were wetted by DMF; the surface properties of the coatings depended on the concentration of the polyelectrolyte added to the dispersion. The polyelectrolyte adsorption on F-3 and pigment particles was estimated by the UV spectroscopy; the electrokinetic potential of the particles was measured. The charge on a particle surface increased the dispersion stability, thus facilitating the formation of a more uniform electrodeposited layer, i.e., the coating.     

Stokesian Dynamics Simulations of Ferromagnetic Colloidal Dispersions Subjected to a Sinusoidal Shear Flow

We have conducted Stokesian dynamics simulations to investigate the dynamic properties of ferromagnetic colloidal dispersions subjected to a sinusoidal shear flow. Thick chain-like cluster formation is significantly influenced by an oscillatory shear flow even if the amplitude is relatively small, since the internal structures of thick chain-like clusters are highly sensitive to the change in the direction of the shear flow. The motion of thick chain-like clusters is out of phase to a sinusoidal shear rate, and the phase difference is strongly correlated with that of the viscosity and normal stress coefficients. The viscoelastic properties become more apparent with decreasing frequency of the oscillatory shear flow, since such properties have a strong relationship with the thick chain-like cluster formation. In other words, since thick chain-like clusters are more stable for the case of a smaller frequency shear flow, such stable clusters induce significant viscoelastic properties of ferromagnetic colloidal dispersions in a strong, applied magnetic field. Copyright 2000 Academic Press.     

关于稀溶液依数性讲解中的几个问题讨论

就大一化学中稀溶液依数性讲解中依数性概念、蒸气压下降原因、渗透压定义以及几个图解中存在的问题进行讨论并提出了见解。