Research on the rheological properties of cross-linked polymer microspheres with different microstructures

Abstract

Polyacrylamide is widely used in various fields as the controlled releasing of medicines, paper and other basic fields. For purposes of enhancing oil recovery, polymer microspheres are utilized as in-depth flooding agent for their excellent performance of water shutoff and deep profile control. To explain the thickening properties of copolymer intermolecular, study of the interaction between solution properties and microspheres structure is necessary. Cross-linked polymer microspheres with different microstructures were synthesized by changing the crosslink ratio Nx. When the mass concentration was sufficiently high, the aggregated microspheres would be broken up under the shear stress; therefore, the dispersed system exhibited shear-thinning behavior. At lower mass concentrations, the rheological properties were markedly different. With an increase of Nx(0.5%-10%), the microspheres behaved as pseudoplastic fluid, Newtonian fluid and dilatant fluid in turn with the increase of shear rate. Additionally, the critical mass concentration (above the mass concentration, the cross-linked microspheres displayed shear-thinning, thixotropic behavior, a sol-gel transition and creep-recovery behavior) increased with the increasing crosslink ratio.