The rheological behavior of polyacrylamide solution - II. Yield stress

The effect of temperature and concentration on the rheological behavior of polyacrylamide solution was systematically studied using the generalized Casson equation. It was found that the yield stress of the polyacrylamide solution decreased with increasing temperature and increased with increasing concentration. The consistency coefficient of polyacrylamide solution increased and flow behavior index of polyacrylamide solution decreased on increasing the temperature. It was found that the effect of temperature on the yield stress, consistency coefficient and flow behavior index of polyacrylamide solution of different concentrations followed an Arrhenius-type relationship. Moreover, the consistency coefficient of the polyacrylamide solution increased and flow behavior index of polyacrylamide solution decreased on increasing the concentration of polyacrylamide. The general rheological equation, optimal in terms of multiple correlation coefficients, was established and confirmed by experimental data. The optimum equation: tau=tau (o)+K gamma (n) where tau (o)=5.0x10(-9) exp(0.0644C+38000/RT), n=0.3586 exp(-0.0017C+3700/RT) and K=7.469 exp(0.0157C-28100/RT), was given for describing the combined effect of temperature and concentration on the behavior properties of low concentrations of the polyacrylamide solution. The equation was successfully applied in calculating the rheological behavior of polyacrylamide solution. (C) 2001 Elsevier Science Ltd. All rights reserved.