Mechanism and Dissolution Process of Amphoteric Polyacrylamide As Dispersant

Amphoteric polyacrylamide is formed by hydrolyzed copolymerization of acrylamide and ethylene-based cationic monomer acrylic acid. Through infrared spectroscopy analysis, the product chain contains not only carboxylate ions but also ethylene-based cationic charges, forming an irregular copolymer with both cationic and anionic charges on the molecular chain.

Role of amphoteric polyacrylamide as a dispersant

Surfactants can fully wet and evenly disperse solid suspended particles in the liquid phase, minimize system separation and aggregation, and reduce the sedimentation rate of solid particles, thereby maintaining the dynamic stability of the suspension. As the molecular chain of amphoteric polyacrylamide contains carboxylate, it reduces surface tension and is beneficial for wetting the solid substances in water, especially for fiber and fillers'dispersion.

When PAM powder is added to the slurry, it forms a bimolecular structure on the surface of fibers and fillers. The external dispersant has a strong affinity with water, increasing the wetting level of fiber and filler particles with water. Due to electrostatic repulsion, solid particles like fibers and fillers move away from each other to achieve good dispersion effect.

Solubilization process of amphoteric polyacrylamide

Although Amphoteric polyacrylamide is soluble in water, it forms an opaque gel when the dissolution concentration exceeds one-percent level, making it difficult to continue the dissolution process. Therefore, a certain amount of clear water needs to be added in advance until the stirring blades are completely submerged, initiating the stirring device to circulate the aqueous solution, and then adding PAM powder.

The stirring blade should not have any corners and blades to avoid poor effects such as sticking and shearing of the copolymer molecular chain, making the dissolution concentration inaccurate and weakening its dispersing effect. The solubilization concentration of amphoteric polyacrylamide is not excessive, generally around 0.5 to 1 ‰.

Amphoteric polyacrylamide is hydrolyzed and copolymerized with both cationic and anionic bases. Its advantage is that it possesses the characteristics of general cationic flocculants, which can recover valuable metals from strong acid-extracted ores or acid catalysts containing metal. Anionic and cationic polyacrylamide types cannot be mixed. If they are used together, precipitation will occur. Therefore, amphoteric polyacrylamide is the most ideal.