In situ Dynamic Rheological Study of Polyacrylamide during Gelation Coupled with Mathematical Models of Viscosity Advancement

Abstract

Acrylamide dynamic viscosity has been measured in aqueous solutions. Separate rheological measurements were performed on neat resins devoid of the curing agent over a range of shear rates to yield the initial resin viscosity. The gels were also characterized by sub-ambient DSC to determine the phase structure as a function of formulation. The dynamic viscosity shows a marked sigmoidal behavior with a plateau viscosity. Mathematical interpretations of the gel time both by sigmoidal and power law models were comparable. The power law model allowed a direct determination of the gel time while the sigmoidal model yielded parameters associated with the initial viscosity, one associated with the plateau viscosity of the gel, and two time constants controlling the sharpness of the transition.