Rheological Behavior Of Aqueous Solutions Research Articles

Rheological properties of hydrophobically modified alkali-swellable acrysol emulsions

The rheological behaviour of aqueous solutions of two commercial anionic hydrophobically modified alkali-swellable emulsions (HASE), Acrysol TT615 and RM5, was studied. These polymeric systems, initially in the form of low-viscosity latices at low pH, tend to swell and increase their viscosity when neutralised with base. The steady-shear and dynamic properties of these polymers were measured over a wide range of concentration, at constant pH=9 and temperature of 20°C. The intrinsic and zero-shear viscosities were used to identify the concentration regimes of the polymer solutions. In the case of Acrysol TT615, the solution exhibited shear-thinning characteristics at a concentration above 500 ppm. The Carreau model described well the viscosity function of the 1000 and 2000 ppm solutions. Considerable viscosity enhancement and a change in the flow curve profile were observed at concentrations above 2000 ppm. At high polymer concentration. the zero-shear viscosity was not detectable, and the power law model was adequate to characterize these solutions. By contrast, the RM5 solutions exhibited nearly Newtonian behaviour over the whole concentration range considered. Elasticity measured from the first normal stress difference indicated that Acrysol TT615 was more elastic than Acrysol RM5. Dynamic measurements revealed that both storage (G′) and loss (G″) moduli increased with polymer concentration. In the higher frequency and concentration regions, G′ > G″ was obseved for TT615, whereas G″ > G′ for RM5.

Synthesis and rheological behavior in aqueous solutions of poly(acrylamide‐co‐maleic acid)

AbstractWater‐soluble copolymers of acrylamide with maleic acid were synthesized in aqueous solution by using potassium persulfate with N,N,N′,N′‐tetramethyl ethylenediamine as initiator. The influences of synthetic variables on the copolymerization were investigated. The copolymers were characterized by IR and 1H‐NMR spectroscopy. The copolymeric composition was obtained by using 1H‐NMR method. The monomer reactivity ratios were calculated by the Kelen‐Tudos method and the values of r1 (AM) and r2 (MA) were determined to be 11.45 and 0.0129, respectively. The rheological behavior of aqueous solution of synthetic poly(acrylamide‐co‐maleic acid) was determined, and flowing activation energy E was calculated. © 1995 John Wiley & Sons, Inc.

Intense stretching of moderately concentrated polymer solutions

The rheological behaviour of aqueous solutions of high molecular weight polymers with a concentration of the order of several percentages under uniaxial intense stretching has been studied experimentally and theoretically. Sharp acceleration of the relaxational processes was found for high elastic strains. An explanation of the effects observed is offered within the molecular theory of the rheological behaviour of polymeric solutions.

Rheological behaviour of aqueous solutions of polyvinylalcohol in the presence of some nonionic substances

Rheological behaviour of aqueous solutions of polyvinylalcohol in the presence of some nonionic substances

Shear stress and normal stress measurements of aqueous polymer solutions in a cone-and-plate rheogoniometer

The rheological behaviour of aqueous solutions of Separan AP-30 and Polyox WSR-301 in a concentration range of 10–10000 wppm is investigated by means of a cone-and-plate rheogoniometer. The relation between the shear stress and the shear rate is for lower shear rates characterized by a timet0, which is concentration dependent. Both polymers show for 4000 s−1 <\(\dot \gamma \) < 10000 s−1 a behaviour similar to that of a Bingham material, characterized by a dynamic viscosityη0 and an “apparent yield stress”τ0, which also depend on the concentration. The inertial forces are measured for water and some other Newtonian liquids. An explanation is given why the theoretical model developed for these forces does not match the experimental values; the shape of the liquid surface is shear rate dependent. To obtain the first normal stress difference, we have to correct for these inertial forces, the surface tension and the buoyancy. The normal forces, measured for Separan AP-30, appear to be a linear function of the shear rate for 350 s−1 <\(\dot \gamma \) < 3300 s−1.

The flow of non‐Newtonian solutions through packed beds

AbstractThe rheological behavior of aqueous solutions of Separan AP‐30®, polymethylcellulose, and polyvinylpyrrolidone was studied experimentally. These solutions exhibit non‐Newtonian flow behavior in simple shear, and are characterized by one of several 2, 3, or 4 parameter rheological equations. The equations used included the power law, the Ellis model, Spriggs equation, the Herschel‐Bulkley equation, and Meter's model. The power law model fits the data for each of the solutions over a limited range of shear rates, whereas the other models, which include either a lower shear rate limiting Newtonian viscosity, and/or an upper shear rate limiting Newtonian viscosity, or a yield stress, fit the data well over a wide range of shear rates from 0.00675 to 1076 sec−1. The pressure drop‐flow rate data for the same aqueous solutions flowing through packed beds were correlated well by the Ergun equation using the various rheological models applied in this work to evaluate a modified fluid viscosity. In each case it was found that the rheological model which best fit the viscometric data also gave the best packed bed friction factor correlation, and that no one model, such as the powerlaw, or the Ellis model, is the best one to use in all cases for all solutions. For polyvinylpyrrolidone solutions large deviations between experimental values of friction factor and those from the Ergun equation occurred for modified Reynolds numbers greater than one. A pseudo viscoelastic parameter was used to improve the friction factor correlation empirically at high Reynolds numbers.

Relationship between rheological behavior of solutions and composition of acrylamide and acrylic acid copolymers

AbstractThe rheological behavior of aqueous solutions of ten acrylic acid and acrylamide copolymers was studied. The mole fraction of acrylic acid in the copolymer ranged from 0.042 to 0.443. Fifteen aqueous solutions for each copolymer were prepared by including all combinations for five values of the degree of neutralization and for three solution concentrations. All other parameters being constant, solution viscosity increases with the degree of neutralization of carboxylic groups in a copolymer. We introduced the expression (ηn –/(η0n), where ηn and η0 are the viscosities of solution at the degree of neutralization n and 0, respectively, and called it the neutralization viscosity number. It has been found that the limiting neutralization viscosity number for n = 0 is a linear function of the acrylic acid mole fraction in the copolymer with acrylamide and that it is independent of the copolymer molecular weight and solution concentration.