In this work, the reinforcing effects of polystyrene microspheres in a hydrolyzed polyacrylamide (HPAM) matrix was studied. The experimental design approach was used to optimize the rheological behavior of the HPAM polymer. The effects of three important parameters, including the size of the polystyrene microspheres, their concentration, and the test temperature on the zero-shear viscosity of HPAM polymer solutions were considered. (375 characters)