Physical and chemical properties of polyacrylamide
Polyacrylamide is a kind of water-soluble linear polymer polymerized by acrylamide (AM) monomer initiated by free radicals. It has good flocculability and can reduce the friction resistance between liquids. According to the ionic characteristics, it can be divided into four types: non-ionic, anionic, cationic and amphoteric.
Polyacrylamide (PAM) is insoluble in most organic solvents, such as methanol, ethanol, acetone, ether, aliphatic hydrocarbon and aromatic hydrocarbon, except for a few polar organic solvents, such as acetic acid, acrylic acid, chloroacetic acid, glycol, glycerin, molten urea and formamide. However, the solubility of these organic solvents is limited, and they often need to be heated, otherwise they will not have much application value.
Under suitable low concentration, the polyacrylamide solution can be regarded as a network structure. The mechanical entanglement and hydrogen bond between the chains form a network node together. When the concentration is higher, the solution of PAM is gelatinous because the solution contains many chains and one contact point. PAM aqueous solution has good compatibility with many organic matters that can be mutually soluble with water, and it is very good for electrolyte. It is not sensitive to amine chloride, calcium sulfate, copper sulfate, potassium hydroxide, sodium carbonate, sodium borate, sodium nitrate, sodium phosphate, sodium sulfate, zinc chloride, boric acid and phosphoric acid.
Polyacrylamide is a white powder or small granule, with a density of 1.32g/cm3 (23℃), glass transition temperature of 188 ℃, and softening temperature of 210℃. Generally, it contains a small amount of water when it is dried, and it will quickly absorb water from the environment when it is dried. The homopolymer separated by freeze-drying method is a white soft amorphous solid, but when it is precipitated from the solution and dried, it is glass. The product is usually dried under appropriate conditions with a moisture content of 5%-15%. The polymer film cast on the glass plate is a transparent, hard and fragile solid.
Application characteristics of polyacrylamide
1. Flocculence: PAM can make the suspended matter through the electric neutralization, bridge adsorption, flocculation.
2. Adhesiveness: it can play a role of adhesion through mechanical, physical and chemical functions.
3. Resistance reduction: PAM can effectively reduce the friction resistance of the fluid, and the resistance can be reduced by 50-80% by adding a small amount of PAM into the water.
4. Thickening property: PAM has thickening effect under neutral and acid conditions. PAM is easy to hydrolyze when pH value is more than 10. The thickening will be more obvious when the structure is semi reticular.