The viscosity of polyacrylamide solution mainly reflects the internal frictional resistance between liquid molecules due to flow or relative movement. The internal frictional resistance is related to the structure of the polymer, the nature of the solvent, the concentration of the solution, temperature, pressure and other factors. The larger its value, the greater the viscosity of the solution.
Temperature
The viscosity of the polyacrylamide solution decreases with the increase of temperature. The reason is that the dispersed phase particles of the polymer solution are entangled with each other to form a polymer with a network structure. The higher the temperature, the easier the network structure is broken, so its viscosity decreases.
Hydrolysis time
The viscosity of the polyacrylamide solution changes with the extension of the hydrolysis time. The shorter the hydrolysis time, the lower the viscosity, which may be due to the fact that the polymer has not had time to form a network structure. Excessive hydrolysis time will cause the viscosity to decrease, which is caused by the loosening of the structure of polyacrylamide in the solution.
Salinity
Compared with the anionic groups in the polyacrylamide molecular chain, the number of cationic groups is larger, the net charge is larger, and the polarity is larger. H2O is a polar molecule. According to the principle of similar compatibility, the polymer has better water solubility and higher intrinsic viscosity. As the content of minerals increases, the positive electrostatic charge part is surrounded by anions to form an ionic atmosphere, thereby combining with the surrounding positive electrostatic charge, the polarity of the polymer solution decreases and the viscosity decreases. The concentration of minerals continues to increase, resulting in a decrease in the solubility of the polymer in water. At the same time, the added salt ions break the association between the positive and negative ions by shielding the positive and negative charges, so that the formed salt bonds are destroyed, which result in a decrease in the solubility of the polymer in water. These two effects compete with each other, so that the viscosity of the polymer solution remains small at higher salt concentrations.
Molecular weight
The viscosity of the polyacrylamide solution increases with the increase of the molecular weight of the polymer. This is because the viscosity of the polymer solution is produced by the interaction between the molecules when the molecules move.