Effect of Heat Treatment on the Flow Properties of Aqueous Guar Gum and Sodium Carboxymethylcellulose (CMC) Solutions

Prolonged heat treatment of 1% (w/v) guar gum and sodium carboxymethylcellulose (CMC) solutions resulted in a permanent loss of their apparent viscosity. The consistency index (K) of the power law model: τ= K γ n , indicated well the loss of viscosity. The reduction in K due to heat treatment could be characterized by D and z parameters. The D 250 and z values for guar gum were 32 min and 62°F, respectively; the magnitudes for CMC were 7.9 min and 48°F, respectively. These values were obtained from experiments in which the solutions were placed in sealed cans (201 × 304) and subjected to temperatures between 210–260°F. Because the solutions were viscous, corrections were made for heating and cooling lags during heat treatment. Dilutee solution viscosity data showed that heat treatment resulted in lower magnitudes of intrinsic viscosities and interaction coefficients. The activation energy of flow of the heat‐treated solutions was not affected significantly due to heat treatment.