The properties of nanoscale water-swellable crosslinked polyacrylamide microspheres were inverstigated by HAAKE rheometer

scanning electron microscopy(SEM) and dynamic lighting scattering(DLS).Besides

filtration experiments with nuclear pore films and displacement experiments of sand packed tube were also adopted to investigate selective plugging characteristics of the nanoscale water-swellable crosslinked polyacrylamide microspheres.The results showed that within a certain range of shear rate

the viscosity of the crosslinked polyacrylamide microsphere dispersed system increased with the raising of shearing rate if the concentration of microspheres was limited in 100 ～ 900 mg/L.This phenomenon showed that the crosslinked polyacrylamide microphere dispersed system represented shear-thickening.The viscosity of 50 mg/L microsphere dispersed systems didn ’t change obviously with shearing rate increasing

which showed newtonian fluid characteristics.The dispersed system with concentration of 1500 mg/L showed pseudoplastic fluid property its viscosity decreased with the shear rate increasing.The grain diameter of crosslinked polyacrylamide microspheres increased and it appeared polydispersitic microsphere in the dispersed system due to swelling

and an obvious size polydispersity was observed.These microsphere dispersed systems exhibited effective plugging on 0.4 μm pore-size nuclear pore film and deep plugging in sand packed tube.This deep plugging property of crosslinked polyacrylamide micorspheres closely depends on their deformability under presssure.