Influence of Oil Content in Paraffins on the Behavior of Wax Emulsions: Wetting and Rheology

In this study, effect and correlation of alkyl chain length (C8, C10, C12, C14, and C16) and concentration of n-alkyl sulfate acid used as representative Br?nsted acid-combined-surfactant catalysts on dehydration esterification of oleic acid with 1-octanol as typical substrates are researched. CMC of the series surfactant are measured by surface tension method. The results indicate that alkyl chain length as well as concentration of catalyst plays an important role in determining conversion of esterifications. Appropriate chain length surfactant and concentration should be chosen for the combined-surfactant catalyzed reaction.     

Dynamic Stability of Heavy Crude Oil-in-Water Emulsions

The transport of heavy oil as concentrated oil-in-water (O/W) emulsions is one of the most promising pipeline techniques, and how to ensure a steady flow is the key to the successful application of this technology. Most of the previous studies focused on the static stability of the emulsions. However, the stability changes constantly with time and external shearing in the transportation. In this paper, a stable O/W emulsion was prepared for its dynamic stability to be tested by three methods of small-scale flow loop, rheology and stirring, respectively. The results indicated that the O/W emulsion with 30 vol.% water and 0.2 wt.% OP-10 could well satisfy the transport requirement. A critical temperature existed to make the rheological property of the emulsion rapidly deteriorate. For low-Reynolds-number turbulent pipe flow, an appropriate increase of temperatures and shear rates was conducive to the flocculation-dissociation balance of the internal phase, which could effectively reduce the apparent viscosity of the emulsion and the flow frictional resistance. High flow rate of O/W emulsions could be transported at relatively low temperatures to ensure great dynamic stability, and low flow rate of that could be done at relatively high temperatures to obtain low apparent viscosity.     

Alteration of Interfacial Stability of Oil-in-Water Emulsions Using Bio-Derived Additives

Oil-in-water (O/W) emulsions are widely used in the preparation of many cosmetics, foods, and pharmaceutical products. Microstructure and stability of such emulsions are of utmost importance for their acceptability by the end user. In the present work, we studied the O/W emulsions to know the effects of two bio-derived additives—juice of Coriander sativam L., and milk of Cocos nucifera L, which have good nutrient value for their use in food emulsions. Addition of Cocos nucifera L. milk resulted in enhanced stability with decrease in the polydispersity of dispersed droplets in the emulsions due to the presence of proteins in it. Addition of Coriander sativam L. provided better stability against pH variation from 4 to 8.     

Effects of Salts Containing Mono-, Di-, and Trivalent Ions on Electrical and Rheological Properties of Oil-Water Interface in Presence of Cationic Surfactant: Importance in the Stability of Oil-in-Water Emulsions

Many industrial applications of oil-in-water emulsions involve salts containing ions of different valence. The properties of the oil-water interface (e.g., interfacial tension, zeta potential and interfacial shear viscosity) are strongly influenced by the presence of these salts. This work investigates the role of NaCl, CaCl₂ and AlCl₃ on these properties of the hexane-water interface in presence of a cationic surfactant, viz., hexadecyltrimethylammonium bromide. Addition of salt enhanced the adsorption of surfactant molecules at the hexane-water interface, which increased the interfacial charge density, and consequently, the zeta potential. Interfacial shear viscosity significantly decreased in the presence of salt. The effectiveness of salt at a given concentration was in the sequence: AlCl₃ > CaCl₂ > NaCl. The hexane-in-water emulsions coarsened with time due to the coalescence of hexane droplets. The increase in droplet size with time was analyzed by a model based on the frequency of rupture of the thin aqueous film. The rate constants for coalescence were determined. The rate of coalescence increased in presence of salt.      

Rheological Behavior and Scattering Studies of Acrylamide-Based Copolymer Solutions

Summary: In this paper the chemical structure of an acrylamide-N,N-dihexylacrylamide copolymer was established by IR and NMR. Static and dynamic light scattering in formamide were used in order to evaluate the polymer structural parameters, such as weight-average molecular weight (M_w), second virial coefficient (A₂), radius of gyration (R_G), the form factor P(q) and the hydrodynamic radius (R_H). Additionally to the classical characterization, those results indicated the presence of aggregation, showing that formamide is not a very good solvent, as stated in earlier investigations. The rheological behavior in aqueous solutions was evaluated as a function of the salt concentration. The solutions presented an important viscosity increase in the presence of NaCl and did not show any sensitivity to the presence of CaCl₂. This result is in favor of the oil recovery especially in high salinity reservoirs.     

Flocculation and Coalescence of Oil-in-Water Poly(dimethylsiloxane) Emulsions

The stability of poly(dimethylsiloxane) (PDMS) oil-in-water emulsions has been investigated in the presence of added NaCl as well as in the presence of added surfactant. The emulsions were prepared using a combination of nonionic (C(x)E(y), x and y represent the number of methylene (C) and ethylene oxide (E) groups, respectively) and cationic (quarternary alkylammonium) surfactants. The droplets were observed to exhibit weak flocculation in the presence of high NaCl concentration (1 M). Phase separation and optical microscopic observations revealed that the principal mechanism for emulsion destabilization at high salt concentration was coalescence, which was accelerated at elevated temperature (50 degrees C). The effective coalescence rate for diluted emulsions was investigated using photon correlation spectroscopy. The small effective Hamaker constant for PDMS is the primary reason for the slow rate of coalescence observed for the emulsions at neutral pH in the presence of NaCl. The stability of PDMS emulsions to flocculation is qualitatively similar to that reported for low Hamaker constant dispersions (e.g., microgel particles). Addition of cationic surfactants (cetyltrimethylammonium chloride and dodecyl dimethylbenzylammonium chloride) to the negatively charged droplets after preparation was shown to decrease the emulsion stability once the surfactant concentration exceeded the CMC. Electrophoretic mobility measurements showed that added cationic surfactant changed the sign of the droplet charge from negative to positive at concentrations well below the CMC. Charged micelles of the same sign as the droplets are electrostatically excluded from close approach to the droplet surface within a distance (varepsilon) which results in depletion flocculation. Copyright 2000 Academic Press.     

Analysis of the Rheological Behavior of Copper Metal Injection Molding (MIM) Feedstock

Metal Injection Molding (MIM) technique allows for the production of highly porous metallic foams with porosity levels up to 90%. It makes use of the pressure built up by the decomposition of a foaming agent which is incorporated in a foamable precursor copper material obtained by powder compaction. Rheological is one of the key factors to ensure the successful of MIM technique and to predict failure, whether due to the binder component and compositions, powder loading or unsuitable process parameters. The balanced ratio feedstock contains of 63 vol.% of copper powder, different percentage of potassium carbonate; Batch 1 (0.4 vol.%), Batch 2 (0.5 vol.%) and Batch 3 (0.6 vol.%), and the remaining volume percentage of binder system has been mixed to form copper feedstock. The rheological behaviors were investigated using a capillary rheometer (CFT-500D, Shimadzu) at various temperature and loads. From the experiments, it was concluded that the MIM feedstock exhibit a shear thinning or pseudo-plastic behavior based on the trend of graph which is suitable for MIM process. This result is within the ideal range of viscosity theoretical for MIM feedstock which is in the range of between 10 Pa.s to 1000 Pa.s at all temperature tested. The viscosity of a pseudo-plastic substance decreases as the shear rate increases (shear thinning). This could be due to particle orientation and ordering with flow as well as breakage of particle agglomerates released together with the binder.     

超润湿膜在乳化液破乳中的应用及作用机制

超润湿膜材料由于对水和油有独特的润湿性质,可显著提高膜材料处理乳化液的通量,有效缓解严重的膜污染问题,因此在乳化液废水处理领域受到越来越多的重视。本文从超润湿膜的设计制备、分离效果和作用机制三个方面进行分析和总结。超润湿膜材料包括超亲水膜、Janus膜和功能位点膜,主要通过构建亲水表面和粗糙结构进行膜的设计制备,其中静电纺丝法合成的交联纤维膜由于可以突破筛分效应对膜孔径的限制,在乳化液分离中具有较好的应用前景。同时,归纳超亲水膜的滤水破乳模式和Janus膜的集油破乳模式,前者具有操作压力低、过滤通量高、抗污染性能好的特点,后者具有高纯度集油的特点;并分析膜润湿性、膜孔径、膜上功能位点等膜结构性质和表面活性剂浓度大小等因素对乳化液破乳分离效能的影响规律。最后,总结液滴在膜垂向和切向上的迁移转化规律,以及在Janus膜集油破乳过程中液滴穿透过膜的机制及其力学分析探讨,该部分研究当前主要是基于液滴形态变化的推测和力学的定性分析,对于相关机制的实证和定量的力学分析还有待进一步探究。     

Rheological characterization of functional walnut oil-enriched butters stabilized by the various polysaccharides

Dynamic rheological measurements provide a valid determination of the ability of polymeric ingredients to compensate the reduced contribution of fat to texture and mouthfeel, as well as provide an emulsion that easily breaks down in commercial low-fat butters. In this study, the linear effects of pectin (PE, 0.5%) and xanthan gum (XG, 0.1%) and their interactions with locust bean gum (LBG, 0.2% and 0.4%), sodium-alginate (ALG, 0.2% and 0.4%), and modified starch (MS, 0.2% and 0.4%) on the flow behavior, dynamic rheological characteristics, and stability of reduced-fat butters containing 10% walnut oil (WO) were investigated. Results showed that the power law model can adequately fit the shear-rate/shear-stress data (0.888?≤?r?≤?0.992, p?G′?>?G″ at all frequencies. The samples prepared with PE–LBG (0.2% and 0.4%) and XG–ALG (0.4%) had the highest G′ values. The phase angle (G″/G′) decreased with increasing frequency from 0.03 to 15?Hz. The maximum apparent viscosity and stability were, respectively, found for WO butters formulated with XG–0.2% ALG and PE–0.4% LBG.     

Optimization of Oil-in-Water Emulsion Stability: Experimental Design,Multiple Light Scattering,and Acoustic Attenuation Spectroscopy

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.     

镁铝类水滑石/阳离子淀粉分散体系流变学振荡行为研究

采用稳态剪切和小振幅振荡剪切实验研究了镁铝类水滑石化合物(Mg-Al HTlc)/阳离子淀粉(CS)分散体系(HTlc与CS质量之比R分别为0, 0.02, 0.05和0.08)的流变学性质．实验结果表明: 上述体系在实验pH值(5～11)范围内均为剪切稀释非牛顿流体, 其中, Mg-Al HTlc/CS (R＝0, 0.02和0.05)分散体系的流变曲线符合幂律模型, 而Mg-Al HTlc/CS (R＝0.08)体系符合Herschel-Bulkley模型. 上述体系先于1000 s^－1剪切180 s, 再于1 s^－1(或者3 s^－1)低速剪切时均表观出粘度随时间周期变化的振荡现象. 振荡现象缘于CS分子结构的周期变化. pH值、剪切速率和HTlc含量的变化可以改变振荡周期(频率)和振幅. 低pH值条件下, Mg-Al HTlc/CS (R＝0.08)体系先于1000 s^－1剪切180 s, 再于小振幅振荡剪切(剪切应力0.03 Pa, 频率0.5 Hz)时储能模量G?和损耗模量G?也表现出随时间周期变化的振荡现象.     

Influence of Mixing Speed in Liquid Crystal Formation and Rheology of O/W Emulsions Containing Vegetable Oils

The process parameters are important in the development of emulsions containing liquid crystals. Thus, we studied the influence of the mixing speed in microscopic and rheological features. Oil-in-water emulsions using vegetable oils and nonionic surfactant were developed employing gradual raise of the mixing speed. It decreased the liquid crystal formation and the density values, and increased apparent viscosity values. The most suitable mixing speed was 600 rpm, since it allowed the attainment of emulsion with better performance and presence of lamellar liquid crystals. However, all emulsions were stable in these experimental conditions and presented pseudoplastic behavior and tixotropy.     

取代度和金属平衡离子对羧甲基纤维素热行为的影响

低取代度(DS<0.8)的NaCMC具有纤维素(Ⅱ)型的晶型结构,随DS增加结晶度迅速下降,DS>1时为无定形结构。其T_(?)随DS增加而降低,但DS=1.55的CMC的T_(?)则稍有提高。其起始分解温度(T_(?))随DS增加而增加,而分解活化能则与DS没有规律性的关系。CMC链上的平衡离子H~+、Na~+、Mg~+、Ca~+和Al~(3+)等对其结晶形态的破坏能力不同,对相同价数的离子,随离子半径增大,破坏力增强,而对半径相近的离子,高价的比低价的破坏作用明显。NaCMC的分解活化能E=251～293 kJ/mol,而高价平衡离子的CMC的E=105 kJ/mol左右。     

SDS和CTAB水溶中胶束扩散系数及第一、第二CMC测定

在无探针条件下用循环伏安法测定了不同形状SDS和CTAB胶束的扩散系数，进而得到第一CMC和第二CMC（SDS：第一CMC和第二CMC分别为8．0×10－3和5．6×10－2mol·L-1;CTAB：第一CMC和第二CMC分别为8．9×10－4和2．1×10－2mol·L－1）．此法为表面活性剂体系物理化学性质的研究，特别是为第二CMC测定提供了一个新的研究方法．     

Rheological properties of carboxymethyl cellulose (CMC) solutions

In this study, we investigated the way of predicting two critical concentrations of sodium carboxymethyl cellulose (CMC) solutions using simple experimental procedures with a rotational rheometer. It was found that, above a critical shear rate, all CMC solutions (0.2 to 7 wt.%) exhibit shear-thinning behavior and the flow curves could be described by the Cross model. A first critical CMC concentration c*, transition to semidilute network solution, was determined using the following methods (1) study of the flow curve shapes, (2) Cross model parameters, (3) plot of the specific viscosity vs the overlap parameter, and (4) empirical structure–properties relationships. Furthermore, both creep and frequency-sweep measurements showed that the solutions behaved as viscoelastic materials above a second critical CMC concentration c** (transition to concentrated solution). The characterization of CMC solutions was completed with a time-dependent viscosity study that showed that the CMC solutions exhibited strong thixotropic behavior, especially at the highest CMC concentrations.     

pH-Dependent Aggregation Behavior and Emulsion Stability of Comb-Like Surfactant Containing PEO Grafts

The aggregation behavior of the comb-like surfactant, poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether) (SMA-M), prepared via the one-pot method, at surface and in solution, was investigated by equilibrium surface tension, rheological technology, and transmission electron microscopy (TEM). The emulsion prepared from n-decane/water/C₁₃E₇ was used as a model system to determine the influence of SMA-M on the stability of the emulsion. The equilibrium surface tensions of SMA-M solution with various pH were measured. The adsorption data, that is, the saturation surface excess concentration (Γ_max) and the minimum area (A _min) were evaluated using the average monomeric molecular weight (M _nA ). The results showed that Γ_max decreased with the increase of pH, but the A _min enlarged with the increase of pH. The results of the steady-state shear experiment indicated that the aggregate structure of the as-prepared comb-like surfactant SMA-M in aqueous solution evolved from interlinked micelle-like aggregates to isolated inflated micelle-like aggregates, then to rod-like aggregates with the increasing pH, which were confirmed by the TEM images. The investigation of the stabilization of n-decane/water/C₁₃E₇/SMA-M emulsion system indicated that SMA-M obviously slows down the phase separation, and the most effectively stabilized sample was obtained at pH 5.0. Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

Thermal and Rheological Behavior of Collagen. Chitosan blends

Collagen:chitosan blends in 1:1 ratio were prepared and characterized by Fourier transform infrared spectroscopy, thermal (DSC, TG) and rheological studies. Apparently each material maintains its behavior and addition of chitosan does not denature collagen fibers. The rheological behavior showed that adding chitosan to collagen causes a decrease of storage modulus (G’),viscous loss modulus (G”) and apparent viscosity when measured as a function of frequency. Both anionic and native collagen presented more solid-like behavior than fluid-like viscoelastic behavior. Collagen:chitosan blends exhibits a more fluid-like viscoelastic behavior. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rheological and Morphological Properties of Carboxymethylcellulose/Starch Blends with or without ZnO and Their Applications as Inoculant Carrier

Summary: Using controlled shear-rate testing ramps, this study investigates the rheological properties of carboxymethycellulose (CMC)/starch blends, with and without zinc oxide (ZnO). Viscosity decreased as the amount of starch increased and after adding 1% ZnO. The creep and recovery tests indicated that, with increasing starch content, there was a decrease in elasticity and the viscosity zero shear rate. The results also showed, in the temperature range between 25 and 70 °C, an inversion occurred in the elastic and viscous moduli behavior, obeying the Arrhenius equation. The addition of ZnO affects the viscoelastic behavior and the morphology of the blends. The best survival results were obtained for samples 50/50 and 60/40 wt% (CMC/starch).     

CMC/PNIPAAm半互穿网络水凝胶的溶胀动力学研究

以羧甲基纤维素钠(CMC)和N-异丙基丙烯酰胺(NIPAAm)为原料,制备了具有温度和pH敏感性的半互穿网络(CMC／PNIPAAmsemi-IPN)水凝胶,并研究了水凝胶在不同温度和pH值条件下的溶胀行为。结果表明：在弱碱性(pH-7．4)条件下,凝胶的溶胀速率和溶胀度都随着凝胶中CMC含量的增加而增大;而在酸性(pH-1．O)条件下则相反。在弱碱性条件下,水分子在凝胶中的扩散行为都可用non-Fickian扩散来描述,水分子在凝胶中的扩散系数D随着凝胶溶胀速率的增大而增大;在酸性条件下,20℃时凝胶的溶胀过程符合non-Fickian扩散规律,而37℃时凝胶的溶胀过程符合Fickian扩散规律,但水分子的扩散系数D相差不大。     

Water Sorption to Hydroxyl and Carboxylic Acid Groups in Carboxymethylcellulose (CMC) Studied with NIR-spectroscopy

In carbohydrate systems which contain polar groups such as hydroxyl and carboxylic acid groups, water molecules are adsorbed in a specific way which varies with the type of polar group. Near infrared Spectroscopy (NIR) combined with multivariate statistical analysis was used to study the interactions between water molecules and carboxymethylated cellulose (CMC) with various degrees of substitution of the carboxylic acid groups, in two ionic forms (CMC-Na and CMC-Ca). The adsorbed water molecules were clearly influenced by the counterion; i.e. the nature of the ion-pair. A principle component analysis (PCA) identified variations in the registered spectra related to: the nature of the counter-ion, the degree of substitution (DS), the relative humidity (RH) and the type of polar group to which water was adsorbed. It was, possible furthermore, through the use of partial least square analysis (PLS), to extract spectral information related to the non-freezing bound water adsorbed on hydroxyl and carboxyl groups respectively. Loading spectra indicated that the obtained spectral information indeed correlated to the two kinds of polar groups studied (hydroxyl groups and carboxylic acid groups). The results support the view that, in the humidity range of 0–100%, water molecules are specifically adsorbed to individual polar groups, which characteristics are dependent on the nature of the polar group.