Factors Affecting The Viscosity Of Polyacrylamide

    Polyacrylamide (PAM) is a homopolymer of acrylamide or copolymerisation with other monomers to get the polymer of the collective name, is a water-soluble polymer in one of the most widely used varieties. Due to the polyacrylamide structural unit contains amide group, easy to form hydrogen bonds, so that it has good water solubility and high chemical activity, easy to get through the grafting or crosslinking of branched chain or network structure of a variety of modifiers, in the petroleum exploration, water treatment, textiles, paper, mineral processing, medicine, agriculture and other industries have a wide range of applications.

    The viscosity of polyacrylamide solution mainly reflects the internal friction resistance between liquid molecules due to flow or relative motion. Internal friction resistance and the structure of the polymer, the nature of the solvent, the concentration of the solution and the temperature and pressure and other factors, the larger its value, indicating that the greater the viscosity of the solution.

    1, the effect of temperature on the viscosity of polyacrylamide

Temperature is a reflection of the intensity of the molecular irregular thermal movement, the movement of molecules must overcome the intermolecular interaction forces, and intermolecular interactions, such as intermolecular hydrogen bonding, internal friction, diffusion, molecular chain orientation, entanglement, etc., directly affect the size of the viscosity, so the viscosity of the polymer solution will change with the temperature. The effect of temperature change on the viscosity of the polymer solution is significant. Polyacrylamide solution viscosity with the increase in temperature and decrease, the reason is that the polymer solution of the dispersed phase particles entangled with each other to form a mesh structure of the polymer, the higher the temperature, the easier the destruction of the mesh structure, so its viscosity decreases.

    2, hydrolysis time on polyacrylamide viscosity effect

Polyacrylamide solution viscosity with the prolongation of the hydrolysis time and change, hydrolysis time is short, the viscosity is small, which may be due to the polymer is too late to form a reticulated structure; hydrolysis time is too long, the viscosity decreases, this is the polyacrylamide structure in solution due to the loosening. Partially hydrolysed polyacrylamide dissolved in water dissociated into negatively charged macromolecules, intermolecular electrostatic repulsion and the same molecule on the anionic repulsive force between different chain links lead to molecules in solution and can make the molecules entangled with each other, which is the part of the hydrolysed polyacrylamide solution viscosity can be significantly increased for the reason.

    3, the effect of mineralisation on the viscosity of polyacrylamide

Polyacrylamide molecular chain of cationic groups relative to the number of anionic groups, more net charge, polarity, and H2O is a polar molecule, according to the principle of similar solubility, the polymer water solubility is better, the characteristics of the viscosity is larger; with the increase in mineral content, the positive electrostatic charge partially surrounded by anions to form an ionic atmosphere, so that with the surrounding positive electrostatic charge combination, the polymer solution polarity decreases, the viscosity decreases Mineral concentration continues to increase, positive and negative ionic groups form intramolecular or intermolecular hydrogen bonding (resulting in a decrease in the solubility of the polymer in water), while the addition of salt ions through the shielding of the positive and negative charges, dismantling the positive and negative inter-ionic bonds have been formed to the salt bond is damaged (resulting in an increase in the solubility of the polymer in water), the two roles of the competition with each other, so that the polymer solution in the higher salt concentration (>0.06%). Salt concentration (> 0.06 mol / L) under the viscosity to remain small.

    4, the molecular weight on the viscosity of polyacrylamide

The viscosity of polyacrylamide solution increases with the increase of the molecular weight of the polymer, which is due to the viscosity of the polymer solution is generated by the intermolecular interactions during the molecular movement. When the relative molecular mass of the polymer is about 106, the polymer nematic clusters begin to interpenetrate each other enough to affect the scattering of light. At slightly higher levels mechanical entanglement is sufficient to affect viscosity. At fairly low levels, the polymer solution can be regarded as a web, with interchain mechanical entanglements and hydrogen bonds combining to form the nodes of the web. At higher contents, the solution contains many chain-link contacts, giving the polymer solution a gel-like consistency. Therefore, the greater the relative molecular mass of the polymer, the easier it is to form chain entanglements between molecules and the greater the viscosity of the solution.