Structure-property relationships of new water-soluble grafted starches with amphoteric character

Full Paper: In an attempt to develop an environmentally friendly, multifunctional mud additive for oilfield drilling treatment, new water-soluble grafted starches with amphoteric character were prepared by grafting the mixed monomer system of 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and 2-(dimethylamino)ethyl methacrylate (DMAEM) onto naturally occurring potato starch, and characterized by IR and composition analyses. Their structure-property relationships with respect to the hydration suppression of the swellable clay and the control of mud rheology were studied with the help of clay hydration-swelling test, mud rheology test, and SEM observation. It has been found that the grafting of DMAEM enhances the inhibition effectiveness of clay hydration-swelling and that the grafting of AMPS increases the viscosity of the treated muds and the tolerance to added salt. Compared with the partially hydrolyzed polyacrylamide with a degree of hydrolysis of 16%, a typical polymeric additive used in current drilling fluids; such grafted starch with suitable grafting percentage and composition has some distinct advantages in the formulation of water-based drilling muds.