Extension rheology behaviors of polyacrylamide and its copolymer in aqueous solution

Extension viscosity is one of the important parameters for the efficiency of polymer flooding. By means of CaBER1 extensional rheometer and RS 600 rheometer,the extension viscosity and rheological behaviors of polyacrylamide and its copolymer in aqueous solution were measured and the effect of polymer chain structures upon the extension viscosity and rheologic behaviors was studied. It has been found that the extension viscosity of polymer solution is greater than the shear viscosity of polymer solution at the same strain rate by three orders of magnitude or more,and it increases with the increase of strain but decreases with the increase of the strain rate. The extension viscosity of the comb-shaped polyacrylamide copolymer is much greater than that of the partially-hydrolyzed polyacrylamide homopolymer in case of the same concentration. In particular,the extension viscosity of the polyacrylamide copolymer solution is three to five times greater than that of the homopolymer solution on condition that they have the same shear viscosity,and the elastic model of the copolymer solution is 1.8 times greater than that of the homopolymer solution. The extension viscosity of both polyacrylamide and its copolymer in solution increases swiftly as the concentration of polymers in solution increases.