Predicting Steady and Oscillatory Shear Rheological Properties of CMC/Guar Blends Using the Bird‐carreau Constitutive Model

The Bird‐Carreau constitutive model, a five parameter semi‐empirical set of equations, was used to predict the steady shear viscosity η, the dynamic viscosity η′, and the out‐of‐phase component of the complex viscosity divided by frequency η″/ω, for aqueous blends of sodium carboxymethylcellulose (CMC) and guar gum. The five Bird‐Carreau constants were derived from equations which correlate the constants to concentration and molecular weight of the CMC/guar blends. Blends of ratios 3:1, 2:1, 1:1, 1:2, and 1:3 by weight were studied in concentrations of 0.5, 0.75, 1.0, and 1.5% by weight. For most blends the model accurately predicted the experimental η and η′ data in the frequency/shear rate range of 0.1–100 s‐1 and the experimental η″/ω data in the frequency/shear rate range of 1.0–100 s−1.