Study of the rheological and compatibility behavior of sulfonated acrylamide copolymer/ wheat starch blends in aqueous media

In order to develop the scope of application of polymer materials in the preparation of drilling fluids, in this study, various blends of wheat starch and copolymer of sulfonated polyacrylamide were prepared and the rheology and compatibility behavior of samples under different salinity and aging conditions were evaluated. The rheological behavior of starch-polyacrylamide blends in tap water and saturated brine water showed that the viscosity of the samples increased with increasing concentration of polyacrylamide copolymer in the both media. However, starch-polyacrylamide blends in saturated brine had less viscosity than tap water. It was observed that in both tap water and salt water saturated conditions after 4 hours of aging at 90 ° C, the viscosity of most samples increased. Comparison of the curves for empirical viscosity data and prediction of the mixing rule showed that in both of tap water and salt saturated water, positive deviation from the mixing rule is observed, which indicates the compatibility between the blend components. By performing the aging process, although positive deviation was still observed, this positive deviation slightly decreased, which means the negative effect of aging on the compatibility of the starch- copolymer of sulfonated polyacrylamide blend.
In conclusion, the results of this study showed that the blend of starch- sulfonated polyacrylamide copolymer is compatible at high temperature (90 °C) and saturated NaCl salt wate. Moreover, in some samples, this compatibility exists even after aging.