Rheology Analysis of Molecular Structures of Modified HPAM Polymers on Heat Resistance

Adding functional monomers to improve heat resistance of Partially hydrolyzed polyacrylamide (HPAM) becomes a hot point in recent years. However, to fully comprehend the impact of the molecular architectures of the functional monomers on heat resistance, more research is still needed. Four polymers with the main chains of acrylamide (AM) and adding other functional agents were synthesized through free radical polymerization, and their structures were characterized. To ascertain the heat resistant performance, the viscosity, viscosity retention rate and viscosity recovery of the polymers were evaluated. At last, explain how the molecular structure of the polymer affects temperature resistance by comparing the viscoelasticity properties of polymers before and after structural breakdown. The results showed that the viscosity of the four distinct polymers decreased as temperature rose and even showed a trend toward irreversible viscosity loss at temperatures over 70 ℃. At 90 ℃, the irreversible viscosity loss was lowest in polymers containing N’ N-dimethylacrylamide (DMAA), at 37.8%, and highest in polymers containing Dodecyl phenol polyoxyethylene ether (DP), at 70.9%. The viscoelasticity analysis demonstrated that all storage modulus of the four polymers before aging were higher than their loss modulus, while after aging, the opposite trend emerged, which proved that the irreversible loss of viscosity was caused by the destruction of the spatial network structure due to the main chain broken under high temperature. Besides, the small decrease of the storage modulus and huge shear viscosity loss of PAADA manifested that the hydrophobic association and steric hindrance effects of polymer monomers with branching structures worked synergistically to reduce the chain broken. This suggests that functional monomers with branched structure and hydrophobic structures may be a better option for increasing heat resistance. This paper lay a theoretical foundation in rheology for the modification of HAPM with better heat resistance.