For the viscosity of anionic polyacrylamide products, there are different demands in different fields. For example, ultra-high viscosity products are needed in the oil field, because manufacturers are "trying hard" to increase the molecular weight. In the field of water treatment, sometimes the high molecular weight will be counterproductive, because its viscosity will rise linearly with the increase of molecular weight. The direct consequence is that the screen sticking phenomenon occurs during the use of the filter press and the wire drawing phenomenon of the mud cake, that is, we often say that the dehydration is not good.
Sometimes, in the face of some special user groups, how to effectively improve the viscosity of anionic polyacrylamide has also become an urgent problem for manufacturers. Here, the viscosity we say refers to the viscosity at a certain concentration and temperature. For the existing anionic polyacrylamide, its molecular weight is certain and its viscosity at a certain concentration is also certain. Generally, the viscosity of polyacrylamide that has been produced can not be improved, unless cross-linking agent is added to make it partially branched or crosslinked to change the hydrodynamics of anionic polyacrylamide, which can indeed improve its viscosity to a certain extent.
The polymer chain of anionic polyacrylamide has great resistance to flow in aqueous solution, so its aqueous solution viscosity is high, and this viscosity varies with the concentration, molecular weight and degree of hydrolysis of PAM.
Generally speaking, when other conditions are the same, the greater the molecular weight, the higher the viscosity of the aqueous solution. The higher the concentration, the higher the viscosity. With the increase of degree of hydrolysis, the viscosity increases. When the degree of hydrolysis is about 50%, the viscosity decreases slightly after reaching the maximum.
In addition, the viscosity also decreases with the increase of temperature and the salinity of the solution. Anionic polyacrylamide aqueous solution has good lubrication performance. It can adhere to the solid surface like lubricating oil to form a film with good lubricity and greatly reduce its friction. Therefore, the mud cake viscosity coefficient of PAM mud is very small, which can prevent the mud cake from sticking to the drill.