多分散聚合物稀溶液体系的Rouse模型

本文将Rouse提出的均一分布球簧链式分子模型加以推广.得到了多分散体系的本构方程.对几种最常见的分子量分布,在稳态剪切流中,分别计算了它们的物质函数以及特性粘数与重均聚合度的关系.结果表明,这一线性模型的流变性质与聚合物的分子量分布有密切的关系;若通过物质函数的监测,则还能预示聚合反应的动态过程.     

Flow behavior of polyacrylamide solution. III. Mathematical treatment

The flow behavior of polyacrylamide solutions was systematically determined over a wide range of temperatures (20–50°C) and concentrations (20–50 ppm) by using a coaxial cylinder viscometer. The results indicated that the rheological behavior of low-concentration polyacrylamide solution behaves similar to non-Newtonian fluids at all these concentrations. The effect of temperature on the consistency coefficient and flow behavior index of polyacrylamide solution of the different concentrations followed an Arrhenius-type relationship. Moreover, the effect of concentration on consistency coefficient and flow behavior index followed an exponential-law relationship at the temperatures used. The rheological constants for the Arrhenius and exponential-law models were determined. The combined effect of temperature and concentration on the coefficient of dynamic shear stress can be represented by a single equation: shear stress = 2.446 × 10⁻⁷exp(0.0639C + 3613/RT)(shear rate)^{2.337 exp(−0.00707C−245/RT)}. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2784–2789, 2001     

SOLVENT EFFECTS ON THE RHEOLOGY OF AQUEOUS POLYACRYLAMIDE SOLUTIONS†

The influence of solvent chemistry on steady shear viscosity and first normal stress difference for aqueous polyacrylamide solutions (Separan AP-273) was investigated in the Weissenberg rheogoniometer and capillary tube viscometer. It was found that these rheological properties are particularly sensitive to the chemistry of the solvent. For example, the zero shear rate viscosity of a 1000 wppm Separan solution with distilled water as the solvent was greater than that with Chicago tap water as the solvent by a factor of 25, while the first normal force difference varied by a factor of two. The addition of an acid or a base to the Chicago tap water-Separan solution also influenced the zero shear rate viscosity and first normal force difference. It was found that there is an optimum pH of approximately 10 which yields a maximum value of the zero shear rate viscosity for the Separan-tap water solution.

Limited data on the influence of solvent chemistry were obtained for 5000 wppm aqueous solutions of polyethylene oxide (WSR-301) and reveal the same quantitative trends found for the polyacrylamide solutions although the magnitude of the observed changes are smaller.     

Viscoelasticity of concentrated polyacrylonitrile solutions: effects of solution composition and temperature

The effects of solution composition and temperature on the viscoelasticity of concentrated polyacrylonitrile (PAN) solutions were studied using a variety of rheological measurements, such as steady‐state shearing, dynamic stress sweep and transient rheological tests. The first normal stress difference N₁ and the shear stress τ were found to increase with decreasing temperature and increasing PAN concentration and water content in the solutions. The crossover point of N₁ and τ, denoting the equal contribution of viscosity and elasticity to the viscoelasticity of the solutions, moved to lower shear rates at lower temperature, higher PAN concentration and higher water content. The values of the relaxation time (λ) were larger at 70 °C than at 40 °C. In addition, the changes of λ with PAN concentration and water content were different at the two temperatures, ascribed to the different states of the solutions. The PAN solutions were in the linear viscoelastic regime in the temperature range 40–70 °C when the shear stress was below 300 Pa. The creep compliance recovery rate decreased with increasing temperature, but increased with increasing PAN concentration and water content. Thixotropic tests showed that the thixotropy of the solutions was also affected by the solution composition and temperature. Gelation was found to influence the way the solution composition and temperature affected the viscoelastic properties of the PAN solutions. Copyright © 2011 Society of Chemical Industry     

Experimental investigation of the influence of molecular weight distribution on the rheological properties of polypropylene melts

An experimental study of steady shear and elongational flow Theological properties of a series of polypropylene melts of varying molecular weight and distribution is reported. Broadening the molecular weight distribution increases the non-Newtonian character of the shear viscosity function and increases the principal normal stress differences at fixed shear stress. The behavior is compared to earlier rheological property-molecular weight studies. Correlations are developed for these properties in terms of molecular structure. Elongational flow studies indicate that for commercial and broader molecular weight distribution samples, ready failure by neck development occurs and the elongational viscosity appears to decrease with increasing elongation rate. For narrower molecular weight distribution samples, the elongational viscosity is an increasing function of elongation rate, The implication of these experimental results to viscoelastic fluid constitutive equations and polymer melt processing is developed.     

絮凝氧化铁悬浮液流变性质研究

应用LVDV-Ⅲ+型可编程流变仪测定了微米级氧化铁悬浮液絮凝处理后的流变特性,考察因素包括悬浮液固相质量浓度、pH值、絮凝剂添加量、搅拌速度。结果表明,悬浮液浓度不同,其流变性能也表现出不同,在相同剪切速率下,高质量分数悬浮液的表观粘度和剪切应力都大于低质量分数悬浮液的表观粘度和剪切应力;pH对絮凝悬浮液流变性有重要的影响。絮凝悬浮液粘度随pH的增加先增大后减小,絮凝剂聚合氯化铝添加量为80 mg的条件下,pH=6.14时表观粘度最大;絮凝剂浓度的不同,对于悬浮液流变性能的影响也不同,在相同剪切速率下,添加高浓度絮凝剂悬浮液的表观粘度和剪切应力都大于添加低浓度絮凝剂悬浮液的表观粘度和剪切应力,增加絮凝剂浓度对提高悬浮液粘着性能具有积极意义;对悬浮液搅拌强度不同其流变性能也表现出不同,在相同剪切速率下,悬浮液的表观粘度和剪切应力随着测试前对它搅拌强度的增加表现出先增大后减小。     

聚醚砜／二甲基乙酰胺溶液流变性的研究

采用锥板式流变仪研究聚醚砜／二甲基乙酰胺(PES／DMAc)溶液的流变性能。结果表明：PES／DMAc溶液(质量分数为18％～28％)属非牛顿流体中的假塑性流体，表观粘度随温度和剪切速率提高而降低，具有切力变稀行为。溶液的剪切应力随浓度升高而增大，同一剪切速率下，随温度的升高而降低，非牛顿指数(n)值随溶液温度的升高而逐渐增大。     

细菌纤维素/LiCl/DMAC溶液体系流变性的研究

采用锥板式旋转黏度计测定细菌纤维素溶液的流变行为。结果表明,细菌纤维素溶液为非牛顿流体,随着剪切速率的增大,溶液呈现切力变稀现象。溶液中纤维素含量和温度影响纤维素溶液的流变行为,剪切黏度随温度的上升及纤维素含量的减少而下降,结构化程度随温度上升和纤维素含量减少而降低。     

Rheology on novel viscoelastic trimeric octadecyl zwitterionic surfactant micelle solutions

In this work, a novel trimeric octadecyl zwitterionic surfactant (TOCC) was successfully synthesized. TOCC was compounded with sodium salicylate (NaSal) for an optimized formulation to form viscoelastic micelles. The effects of NaSal concentration, pH, and temperature on the rheological properties of TOCC and TOCC/NaSal micelle solutions were investigated. The flow curves for both TOCC and TOCC/NaSal micelle solutions can be fitted with the Carreau–Yasuda model. Zero shear viscosity of TOCC/NaSal micelle solution increased and then decreased with increasing NaSal concentration, and the same trend was observed for viscoelasticity. Some micelle solutions exhibited significant thixotropy with stress overshoot. The optimal composition of the TOCC/NaSal micelle solution obtained was 5.0/0.5 wt%. Frequency sweep in the form of Cole–Cole plots indicated that the viscoelastic modulus of the TOCC/NaSal micelle solution fitted the Maxwell model at low and medium frequencies. With increasing pH, 5.0 wt% TOCC micelle solution had the maximum zero shear viscosity at pH = 6.9. The steady-state viscosities of different concentrations of TOCC micelle solutions reached their maximum at neutral conditions (pH = 6.5 ~ 7.0). Viscoelastic modulus of 5.0 wt% TOCC and TOCC/NaSal (5.0/0.5 wt%) micelle solutions decreased with increasing temperature, and thermal thixotropy was observed in both micelle solutions. The novel TOCC and TOCC/NaSal micelle solutions enrich the variety of trimeric surfactants and viscoelastic micelle solutions. This study provides a rheological reference for the applications of viscoelastic trimeric surfactants in smart materials and oil fields.     

ABS/木质素复合材料动态流变行为的研究

通过酸析法从木质素磺酸钙中提纯木质素,利用熔融共混法制备了丙烯腈丁二烯苯乙烯共聚物（ABS）/木质素复合材料,采用旋转流变研究了复合体系的动态流变行为。结果表明,经过提纯后,木质素磺酸钙在波长622 cm-1处的SO伸缩振动吸收峰消失;在线性黏弹区内,复合体系的储能模量（G′）保持恒定,当应变（γ）超过临界值γc时,复合体系进入非线性黏弹区,出现了“Payne效应”,G′随着γ增大而骤然减小,而且随着木质素含量的增加γc下降;随着剪切速率的增加,复合材料的复数黏度（η*）呈下降趋势,表现出剪切变稀的特征;随着木质素含量增加,复合体系的η*增大,储能模量（G′）和损耗模量（G″）交叉点黏弹转变频率(ωc)呈先增大后减小的趋势。     

聚丙烯腈/离子液体溶液流变性能的研究

采用应力流变仪对聚丙烯腈/1-丁基-3-甲基咪唑氯化物(PAN/[BMIM]Cl)溶液体系的稳态和动态流变性能进行了研究,讨论了PAN相对分子质量(Mη)对溶液稳态和动态流变性能的影响。结果表明:PAN/[BMIM]Cl溶液在低剪切速率区表现出牛顿流体特征,在高剪切速率区随着剪切速率的增大粘度降低,表现为切力变稀流体;溶液的粘度大于常规溶剂体系,随着PAN的Mη增大,PAN/[BMIM]Cl溶液表观粘度明显增大,非牛顿指数减小,粘流活化能增大;溶液的损耗模量和储能模量越大,溶液更容易表现出弹性效应。     

多孔SiC中黏弹性流体的流变性数值研究

为研究黏弹性流体在多孔SiC中流变行为,将多孔SiC的骨架建成十四面体结构单元的阵列,利用POLYFLOW计算流体力学软件,黏弹性流体的本构方程采用PTT模型,主要研究黏弹性流体流经多孔SiC的法向应力及剪切应力随松弛时间、多孔介质孔径以及流速变化规律,以及剪切速率的分布特点。黏弹性流体弹性越强,孔道结构对其作用的应力越大,从而使聚合物分子链发生断裂的几率越大。     

纤维素纳米晶体对壳聚糖纺丝原液流变行为的影响

首先将纤维素纳米晶体(CNC)悬浮液进行超声分散,然后与壳聚糖乙酸溶液进行高速搅拌共混,制备不同CNC含量的壳聚糖-CNC共混均匀溶液。采用平板式旋转流变仪研究了CNC含量对壳聚糖溶液流变行为的影响。测试结果表明:壳聚糖-CNC共混溶液表现为非牛顿流体行为;黏度随温度的上升而下降,但在高剪切速率范围内,温度对黏度的影响不再明显;随着CNC含量的增加,壳聚糖溶液的表观黏度增大,对剪切速率的敏感性增强,同时非牛顿指数和黏流活化能降低;共混原液的结构黏度指数随CNC含量减少以及温度升高而降低;壳聚糖-CNC共混溶液储能模量和损耗模量的交叉点随温度的升高向高频区移动,随CNC含量的增加向低频区移动,溶液流变规律基本符合Cox-Merz规则。     

Nonlinear rheological behavior of a novel oil displacing agent

In this work, the shear and elongational rheologies have been investigated for a newly developed oil displacing agent, polymeric surfactant‐PSf. It was found that the PSf solutions exhibited Newtonian, shear‐thinning, and shear‐thickening behavior, respectively, depending on the polymer concentration and shear rate, and Cox–Merz rule was not applicable to these systems. The first normal stress difference (N₁) versus shear rate plots for PSf were complicated, which varied with the composition of the solutions. The uniaxial elongation in capillary breakup experimental results indicated that Exponential model could be used to fit the experimental data of the PSf solutions at lower polymer concentrations. In addition, it was found that PSf was more effective in improving shear viscosity than partially hydrolyzed polyacrylamide, but not in the case of elongational viscosity. The experimental results indicated that the microstructural mechanisms are responsible for the rheological behavior of the polymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40813.     

MELT RHEOLOGICAL PROPERTIES OF TALC-FILLED ISOTACTIC POLYPROPYLENE COMPOSITES

The melt rheological properties of talc-filled isotactic polypropylene have been studied at talc concentrations of 0–33.3 vol% and at 493 K. The composites followed a power law model in the shear stress–shear rate dependence and were shear thinning. The apparent melt viscosity increased whereas the melt elasticity parameter “first normal stress difference” decreased as the talc concentration increased. Surface modification of the talc by a coupling agent LICA 38 modified the rheological properties through bonding and/or a plasticizing/lubricating effect.     

用于制造极细纤维的PET/PE共混熔体流变性及粘弹性研究

本文采用自制CE—81型毛细管流变仪研究了PET/PE共混物体系的流变性和粘弹性。结果表明:在所研究的温度和切变速率范围内,随PET含量的增加,PET/PE共混物体系的表观粘度η_a以及剪切弹性模量G下降,可复弹性形变Sr及第一法向应力差(σ_(11)—σ_(22))增加。     

Shear rheology of diluted solutions of high molecular weight cellulose

A steady-state and dynamical rheological study was performed with dilute solutions (1–4%) of high molecular weight cellulose (M_w = 350,000). The solutions are strongly viscoelastic. The steady-state viscosity and the first normal stress difference have a power law dependence on the shear rate. The power law indices have the same dependence on temperature and concentration. These results as well as the correlation between the steady-state viscosity and the real part of the complex viscosity are in good agreement with the Spriggs model. The 4% concentrated solution shows the beginning of a rubber-like storage modulus plateau, suggesting the existence of an entanglement network.     

BOPP专用树脂的流变行为研究

利用高压毛细管流变仪,对三种不同BOPP专用树脂的流变性能进行测定,BOPP专用料均表现为剪切应力随剪切速率增加而增加,但增加速率明显减弱,表观粘度随剪切速率增加而减小的特点,具有明显的假塑性的流动行为。通过分析温度、剪切速度和分子量及其分布对树脂的表观粘度的影响,确定不同树脂改善熔体粘度最有效的方法。     

Rheological characterization of concentrated cellulose solutions in 1‐allyl‐3‐methylimidazolium chloride

The rheological properties of high concentrated wood pulp cellulose 1‐allyl‐3‐methy‐limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10–25 wt %). The measurement reveals that cellulose may slightly degrade at 110°C in [Amim]Cl and the Cox–Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120°C. The zero shear viscosity (η_o) was obtained by using the simplified Cross model to fit experimental data. The η_o values were used for detailed viscosity‐concentration and activation energy analysis. The exponent in the viscosity‐concentration power law was found to be 3.63 at 80°C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120°C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G′), the loss modulus (G″) and the first normal stress difference (N₁) were also analyzed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

聚酰胺酸纺丝溶液的流变性能研究

由均苯四酸二酐(PMDA)和4,4'-二氨基二苯醚(ODA)在N,N-二甲基乙酰胺(DMAc)中共聚合制得聚酰亚胺前驱体——聚酰胺酸的纺丝溶液,采用哈克流变仪研究了溶液的流变性能。结果表明:聚酰胺酸溶液属于切力变稀的非牛顿流体;溶液的表观黏度随溶液温度的升高而降低,随溶液浓度的升高或聚合物特性黏度的增大而增大。溶液温度的升高、浓度的降低或聚合物特性黏度的减小均使得聚酰胺酸溶液呈现切力变稀行为的临界剪切速率变大,使得溶液的非牛顿指数增大,同时使得溶液的结构黏度指数减小。溶液的黏流活化能随剪切速率的增加或随溶液浓度的增高而下降。