A study on preparation and thickening efficiency of an inverse emulsion of anionic starch-graft-polyacrylamide

A series of graft copolymers of starch with polyacrylamide was made by using a K2S2O8 initiation system in inverse emulsion. The corresponding anionic graft copolymers, which have a different hydrolysis degree, are prepared by alkaline hydrolysis of the uncharged graft copolymers. Adequate hydrolytic conditions including type and amount of hydrolyzing agent, temperature, and time were studied. These graft copolymers have been tested for their temperature sensitivity, salt tolerance and shear stability, and a comparison has been made with ungrafted polyacrylamide (PAM). Experiments showed that a high hydrolysis degree can be obtained in a shorter time when NaOH and Na2CO3 were used together as hydrolyzing agents, and the highest solution viscosity was observed when the hydrolysis degree of the graft copolymers was approximately 30%. In addition, the shear stability, temperature sensitivity and salt tolerance in the graft copolymers were also investigated.