What are the main factors affecting the viscosity of polyacrylamide?

The viscosity of polyacrylamide solution mainly reflects the internal friction resistance caused by flow or relative motion between liquid molecules. Internal friction resistance is related to polymer structure, solvent properties, solution concentration, temperature and pressure and other factors. The greater the value, the greater the viscosity of the solution.

1, the influence of temperature on the viscosity of polyacrylamide temperature is a reflection of the intensity of molecular random thermal motion, the movement of molecules must overcome the interaction between molecules, and the interaction between molecules, such as intermolecular hydrogen bond, internal friction, diffusion, molecular chain orientation, entanglement, directly affect the size of the viscosity, so the viscosity of polymer solution will change with the temperature. The influence of temperature change on viscosity of polymer solution is significant. The viscosity of polyacrylamide solution decreases with the increase of temperature, the reason is that the dispersed phase particles of polymer solution are entangled with each other to form a network structure of polymer, the higher the temperature, the more easily the network structure is destroyed, so its viscosity decreases.

2, the effect of hydrolysis time on the viscosity of polyacrylamide solution viscosity changes with the prolongation of hydrolysis time, hydrolysis time is short, the viscosity is small, this may be due to the polymer is not too late to form a network structure caused by; The hydrolysis time is too long and the viscosity decreases, which is caused by the structure of polyacrylamide loosening in solution. Partially hydrolyzed polyacrylamide dissolves in water and dissociates into negatively charged macromolecules. The electrostatic repulsion between molecules and the anionic repulsion between different chains on the same molecule lead to the extension of molecules in solution and can make the molecules entangled with each other. This is the reason why the solution viscosity of partially hydrolyzed polyacrylamide can increase significantly.

3, the influence of salinity on the viscosity of polyacrylamide molecular chain cationic groups relative to anionic groups more number, more net charge, larger polarity, and H2O is a polar molecule, according to the principle of similar phase solubility, the polymer water is better, the characteristic viscosity is larger; With the increase of mineral content, the positive electrostatic charge is surrounded by anions to form ionic atmosphere, which combines with the surrounding positive electrostatic charge. The polarity and viscosity of polymer solution decreases. Mineral concentration continues to increase, positive and negative ion groups form intramolecular or intermolecular hydrogen bond association (resulting in a decrease in solubility of polymer in water), at the same time, salt ions added by screening positive and negative charges, break up the association between positive and negative ions, so that the salt bond has been destroyed (resulting in increased solubility of polymer in water), these two effects compete with each other. Making the polymer solution gt at a higher salt concentration; At 0.06 mol/L), the viscosity remained small.

4, the effect of molecular weight on the viscosity of polyacrylamide solution viscosity with the increase of molecular weight of the polymer increases, this is because the viscosity of the polymer solution is produced by the interaction between molecules when the molecular movement. When the relative molecular mass of the polymer is about 106, the polymer wire groups begin to permeate each other enough to affect the scattering of light. At slightly higher concentrations, mechanical entanglement is sufficient to affect viscosity. At relatively low levels, the polymer solution can be viewed as a network structure, with mechanical entanglement and hydrogen bonding between the chains forming the nodes of the network. At higher concentrations, the solution contains many chain-chain contacts, making the polymer solution gel-like. Therefore, the larger the relative molecular weight of the polymer, the easier the formation of chain entanglement between molecules, the greater the viscosity of the solution.