搅拌槽内的液液湍流分散(Ⅰ)——分散特性的影响因素

采用取样稳定显微照相分析法,就稳态液液分散体系,研究了搅拌转速、分散剂浓度、分散相体积分率和分散相粘度对液滴大小及其分布的影响,并用界面张力和界面粘性讨论液-液分散行为,为阐明液-液分散机理提供实验依据。     

HDPE／UHMWPA层状分散合金的亚微形态,流变性能及体系相容性研究

本文研究了HDPE/UHMWPA共混体系的相容性及各组分的流变性能,据此选取了制备层状分散合金的工艺参数,获得了具有各种层状分散相态的共混物。研究结果表明:在低剪切及分散相粘度大于连续相粘度时,分散相易被层化;体系相容性和外剪切场对层状平板的尺寸及形状有明显的影响。     

超浓乳液稳定性的研究

本文简单介绍了超浓乳液的基本概念及用途,并以苯乙烯为分散相,水为连续相,对超浓乳液稳定性进行了详细的研究。研究结果表明,超浓乳液的稳定性与表面活性剂的种类我党有度,分散相性质,分散相的体积分数,电解质浓度,连续相粘度等因素有关。     

乳状液和微乳液体系的形成及其性能研究

以柴油／水、汽油／水、煤油／水为实验体系,制备了乳状液和微乳液并对其性能进行了系统的研究。结果表明：乳状液的粘度是分散相体积分数和粒径的函数并获得了相应的关联式;影响乳状液稳定性的主要因素是乳状液的粒径而不是粘度;在微乳液体系中,表面活性剂的用量和分散相体积之间存在着比例关系;微乳液的形成只与它本身的组成有关而与制备方法无关。     

铬凝胶体系性能影响因素分析

对不同聚合物浓度、交联剂浓度、剪切速率、矿化度及铬凝胶体系性能分析及地层配伍性研究。结果表明:在静态条件下,铬凝胶体系的成胶临界浓度为聚合物浓度500mg·L~(-1)+交联剂70mg·L~(-1)。在预剪切条件下,成胶时间延长,400m·d~(-1)为极限剪切速率,达到这一剪切速率后体系粘度不再降低。随着矿化度的增加,体系粘度上升,当矿化度低于900mg·L~(-1)时体系不成胶。铬凝胶体系与地层配伍的最低渗透率界限为有效渗透率100mD。     

乳状液和微乳液体系的形成及其性能研究

以柴油／水、汽油／水、煤油／水为实验体系，制备了乳状液和微乳液产以其性能进行了系统的研究。结果表明：乳状的粘度是分散相体积分数和料径的函数并获得了相应的关联式；影响乳状液稳定性的主要因素是乳状液的粒径而不是粘度；在微乳液体系中，表面活性剂的用量和分散相体积之间着比例关系；微乳液的形成只与它本身的组成有关而一制备方法无关。     

PP/EHDPET共混体系熔体粘度对相转变的影响

以聚丙烯 (PP) /易水解聚酯 (EH DPET)共混体系为研究对象 ,测试了共混组分在不同加工温度与不同剪切速率下的熔体粘度。结果表明 ,加工温度与剪切速率的改变均会导致 PP与 EHDPET熔体粘度比的变化 ,进而影响到两组分的海 -岛结构构成。选择较高的加工温度及较低的剪切速率 ,可以使共混物 PP在高组成比时成为分散相。     

反应性聚丙烯/三元乙丙橡胶共混物的流变性能研究

采用高压毛细管流变仪 ,研究了EPDM含量、交联剂、交联助剂等因素对反应性PP/EPDM共混物性能的影响。结果表明 ,EPDM分散相浓度为 2 0～ 2 5phr,反应共混工艺对体系的消缠降粘效果显著 ;交联剂A的含量越高 ,体系表观粘度越小 ,但粘度对剪切的响应不敏感 ;交联剂B和并用交联剂S可抑制PP降解 ,进一步优化材料力学性能 ,并仍保持体系加工流动性高于简单共混PP/EPDM。     

调节聚苯乙烯树脂粒度分布的研究

研究了悬浮法聚苯乙烯粒度分布的两种调节方法：改变分散剂用量和改变反应初期分散相粘度。结果表明，分散剂用量增加，树脂粒径减小；分散相粘度增大，树脂粒径增大。     

连续聚合法合成高固含低粘度聚合物多元醇的研究

采用间歇法和单釜连续法合成了高固含聚合物多元醇(POP),采用动态光散射和扫描电镜研究了不同工艺下POP分散相粒子的粒径分布。实验结果表明:采用单釜连续聚合工艺能使POP产品分散相粒子粒径分布比较宽,从而能有效降低高固含POP粘度。采用单釜连续聚合工艺合成出了固含量45％,粘度为 5 900 mPa·s(25℃)的POP。     

The effect of microencapsulated phase change materials on the rheology of geopolymer and Portland cement mortars

The effect of microencapsulated phase-change materials (MPCM) on the rheological properties of pre-set geopolymer and Portland cement mortars was examined. Microcapsules with hydrophilic and hydrophobic shells were compared. The shear rate dependency of the viscosities fitted well to a double Carreau model. The zero shear viscosities are higher for geopolymer mortar, illustrating poorer workability. The time evolution of the viscosities was explored at shear rates of 1 and 10 s⁻¹. New empirical equations were developed to quantify the time-dependent viscosity changes. The highest shear rate disrupted the buildup of the mortar structures much more than the lower shear rate. Microcapsules with a hydrophobic shell affect the rheological properties much less than the microcapsules with a hydrophilic shell, due to the higher water adsorption onto the hydrophilic microcapsules. Shear forces was found to break down the initial structures within geopolymer mortars more easily than for Portland cement mortars, while the geopolymer reaction products are able to withstand shear forces better than Portland cement hydration products. Initially, the viscosity of geopolymer mortars increases relatively slowly during due to formation of geopolymer precursors; at longer times, there is a steeper viscosity rise caused by the development of a 3D-geopolymer network. Disruption of agglomerates causes the viscosities of portland cement mortars to decrease during the first few minutes, after which the hydration process (increasing viscosities) competes with shear-induced disruption of the structures (decreasing viscosities), resulting in a complex viscosity behavior.     

Viscosity and molecular weight distribution of ultrahigh molecular weight polyethylene using a high temperature low shear rate rotational viscometer

To obtain accurate measurements of the limiting viscosity number (LVN) or the intrinsic viscosity [η] of solutions of ultrahigh molecular weight polyethylene (UHMWPE), a low shear floating-rotor viscometer of the Zimm-Crothers type was constructed to measure viscosities at elevated temperatures (135°C) and near zero shear rate. The zero shear rate measurements for UHMWPE whole polymer and UHMWPE fractionated by hydrodynamic crystallization were compared with viscosity measurements at moderate and high shear rates (up to 2000 _s^?1) carried out in a capillary viscometer. The limiting viscosity number of UHMWPE decreases, as expected, with shear rate. The higher shear rate data could not be extrapolated to yield the correct zero-shear rate viscosities. Fractionation of UHMWPE gave 10 fractions ranging in LVN from 9 to 50 dL/g. A tentative integral molecular weight distribution for the whole polymer was calculated on the basis of the Mark-Houwink equation, but because it had been previously established only for lower molecular weight polyethylenes, it may not be accurate. A correlation was found between the LVNs for the fractions in the two types of viscometers.     

Shear viscosity,extensional viscosity,and die swell of polypropylene in capillary flow with pressure dependency

The shear and extensional viscosities of a polypropylene resin were studied using a capillary rheometer and capillary dies of 1‐mm diameter and length of 10, 20, and 30 mm. Melt temperatures at 190, 205, and 220°C and shear rates between 100 and 5000 s^?1 were used. At the highest shear rate a visible melt fracture was observed. An equation relating the pressure drop and die length was derived with consideration of pressure effects on melt viscosities and the end effect. After the correction for pressure effects the true wall shear stress and end effect at zero pressure were calculated. The end effect showed a critical stress of melt fracture around 10⁵ Pa, and increased rapidly when shear stress increased above the critical stress. From shear stress the shear viscosity was calculated, and a power law behavior was observed. Extensional viscosity was calculated from the end effect and showed a decreasing trend when strain rate increased. After time–temperature superposition shift shear viscosity data correlated well, but an upward trend was observed in extensional viscosity when melt fracture occurred. Die swell ratio at different temperatures can be plotted as a function of wall shear stress and was higher for shorter dies. © 2002 Wiley Perioodicals, Inc. J Appl Polym Sci 84: 1269–1276, 2002; DOI 10.1002/app.10466     

Mathematical modeling and the estimation of parameters for the melt viscosity of polyamides

Capillary rheometry data of a range of commercial polyamide engineering materials was obtained from a mould-flow analysis material database, from which melt viscosity data was obtained at different temperatures, which made comparison of the viscosities difficult. In an attempt to make a reasonable comparison between the melt viscosities of the various polyamide materials at different temperatures, it was necessary to obtain the mathematical functions which describe the relationships between: (i) the melt viscosity and the shear rate, (ii) the melt viscosity and temperature and (iii) the melt viscosity and the combined effect of the shear rate and temperature of each of the polyamides studied. Therefore, melt viscosity was modelled as a function of shear rate at the three temperatures (275°C, 295°C and 315°C), at which the viscosities were determined. The function obtained represented smoothed versions of the experimental data, eliminating the experimental noise and enabling the generation of melt viscosity data at the six different shear rates of the original data. It was established that the melt viscosity as a function of shear rate at constant temperature, in the shear rate range 500-700 s m 1 , is incorrectly described by the Ostwald-de-Waele's model, \eta_{\rm T}={\rm f}({\dot \gamma})={\rm K}({\dot \gamma})^{({\rm n}-1)} , while the melt viscosity of the polyamides studied, as a function of temperature, is correctly described by the model \eta_{\dot \gamma}={\rm g}{(\rm T)}={\rm Pe}^{\left (\rm {QT/R}\right )} . But the response-surface melt viscosity is effectively described as a function of both shear rate and temperature by the model: \eta=\vert {\dot \gamma}\vert^{(\rm n-1)}{\rm Ae}^{(\rm ET/R)} . The parameters A, E and n are highly interrelated as they all influence the average melt viscosity. All are temperature sensitive and also, to some degree, shear sensitive.     

Rheological Characterization of Anaerobic Sludge from Agricultural and Bio‐Waste Biogas Plants

Anaerobic sludges taken from 16 different biogas plants were analyzed with respect to their rheological characteristics. All sludges showed temperature‐dependent shear‐thinning behavior with viscosities from 900 – 6000 mPa s at 20 °C. Nevertheless, the liquid fraction of the anaerobic sludges also revealed temperature‐dependent, shear‐thinning behavior with viscosities well above water viscosity (2 – 40 mPa s at 20 °C). The rheological behavior of the liquid phase could be linked to organic fractions, i.e., proteins and polysaccharides. Shear‐thinning and temperature‐dependent behavior was modeled by the power‐law equation and the Arrhenius law, respectively.     

用局部组成理论关联纳米流体的剪切黏度

In this study, a new method is presented to correlate the shear viscosity of nanofluids by local composition theory. The Eyring theory and nonrandom two-liquid (NRTL) equation are used for this purpose. The effects of temperature and particle volume concentration on the viscosity are investigated. The adjustable parameters of NRTL equation are obtained by fitting with experimental data. The calculated shear viscosities for nanofluids of CuO/water with 29 nm particle size, Al2O3/water with two different particle diameters, 36 nm and 47 nm, and CuO/(ethylene glycol, water) are compared with experimental data and the average absolute deviation (AAD) is 1.2%, while the results from some conventional models yield an AAD of 190%. The results of this study are in excellent agreement with experimental data.     

界面剪切黏度对原油乳状液稳定性的影响

对孤东一号联合站及孤东四号联合站(简称孤东1#及孤东4#)两种原油及其分离组分(饱和分、芳香分、胶质、沥青质)配成模拟油,测定了模拟油与碱水〔w(Na2CO3)=1 2%〕体系的界面剪切黏度。原油浓度越大,界面剪切黏度越大;沥青质模拟油/碱水界面剪切黏度最大,在油/碱水间形成了一定强度的界面膜,膜的强度大于饱和分、芳香分、胶质的界面膜强度;孤东4#沥青质模拟油/碱水的界面剪切黏度大于孤东1#沥青质的界面剪切黏度。在剪切速率为0 3rad·s-1时,原油及胶质的油/碱水界面剪切黏度不随时间变化。     

The viscosity of fiber suspensions at low fiber volume fractions

The viscosities of suspensions of glass fibers in an aqueous solution of sucrose have been studied by use of a capillary viscometer. In the aligned condition in the capillary, the viscosity depends little on shear rate within the range studied or on fiber length, but increases with increasing volume fraction of the fibers. The entrance effect was found to depend strongly on fiber volume fraction and fiber length: this indicates that the suspensions are relatively resistant to flow during the initial stages while alignment takes place.     

Measurement of shear-dependent intrinsic viscosities of carboxymethyl cellulose and xanthan gum suspensions

A rotational rheometer with cone and plate fixtures was used to measure the intrinsic viscosities of aqueous suspensions of xanthan gum and carboxymethyl cellulose (CMC). The reduced viscosities or hydrodynamic volumes of CMC suspensions increased with dilution. However, the reduced viscosities of xanthan gum suspensions decreased with dilution within the concentration range of 0.1–0.06% and increased with dilution within the concentration range of 0.04–0.01%. When the gums were suspended and diluted with 0.06 M sodium acetate, the reduced viscosities of all the xanthan gum and CMC suspensions decreased upon dilution. The intrinsic viscosities of xanthan gum and CMC suspensions decreased with increasing the shear rate, showing a dependence of hydrodynamic volume on shear rate.     

Constant rotational rheological behaviors of the PAN/DMSO/nonsolvent systems

The constant rotational rheological behaviors of PAN/DMSO solutions with two kinds of nonsolvent (water and ethanol) have been investigated, respectively, using a cone‐plate rheometer. From viscosity measurements, the flow behavior was described within the shear rate range 0.1–1000 s^?1. The PAN solutions show shear thinning at high shear rates. The viscosities of the solutions decreased with the rising of the temperature at low shear rate. H₂O content has great influence on the viscosity of the solutions, depending on the hydration of H₂O and PAN or desolvent effect, according to different H₂O content. The role of ethanol compared with H₂O was also researched and higher viscosity was found. Non‐Newtonian index, structural viscosity index Δη, and flow activation energy of the PAN/DMSO/H₂O systems were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009