Polyacrylamide, often abbreviated as PAM, is a synthetic high molecular weight polymer with a significant role in several industries. It is composed of acrylamide monomers, hence its name. The characteristics of PAM vary greatly depending on the level of polymerisation, making it an extremely versatile compound.
Polyacrylamides are produced by the polymerization of acrylamide (C3H5NO), a compound obtained by the hydration of acrylonitrile. Acrylamide is usually dissolved in water; it has toxic effects on the nervous system and must be handled under special protective procedures. The dissolved monomers (single-unit molecules) are induced to polymerize (link together to form large, multiple-unit molecules) through the action of free-radical initiators. In the resultant polymer, the acrylamide repeating unit has the following structure:
Polyacrylamide does not have the toxic effects of acrylamide monomer. The polymer is hydrophilic (displays an affinity for water) and can form aqueous solutions of very high concentration. Because of their gel-like properties, these solutions are employed as flocculants in the removal of suspended particles from sewage and industrial effluents (e.g., wastewater from paper mills). Through the highly reactive amide (NH2) group, the polymer can be chemically modified to produce positively charged cationic polymer or negatively charged anionic polymer. Ionic polymers are especially useful in separating metals from residues in various mineral-processing and metallurgical operations.
Polyacrylamides are widely used in an uncrosslinked form as thickeners and flocculants in the oil industry, ore recovery, water and sewerage treatment, and a variety of industrial and consumer products. Crosslinked polyacrylamides, particularly when partially hydrolyzed to yield acrylic acid moieties, are superabsorbent gels and have been used in selected applications over the years. Nonhydrolyzed, and hence nonionic, polyacrylamide gels are used for electrophoresis media in biotechnology laboratories . Particulate polyacrylamide gels are useful in horticulture.
Hydrolysis of polyacrylonitrile can yield first polyacrylamide and eventually some acrylic acid groups. Because polyacrylonitrile can be readily formed into fibers, it has been possible to form absorbent fibers by hydrolyzing the surface of such materials .
Acrylamide monomer is a solid, but the typical commercial product is a 50% solution in water. The monomer is a neurotoxin, and attention to safe handling is essential; the liquid form allows less opportunity for physical contact and is therefore safer.
Several properties make polyacrylamide a crucial compound in various applications. These include its high water solubility, ability to form gels, and its versatility in changing its physical properties through modifications in the polymerisation process.
- Water Solubility: PAM is highly soluble in water due to the presence of amide groups, which can form hydrogen bonds with water molecules. This property is essential in many of its applications, including wastewater treatment and soil conditioner.
- Gel Formation: When crosslinked, polyacrylamide forms a gel-like substance. This attribute makes it useful in several industries, including the cosmetic industry where it is a common ingredient in moisturizers and other skincare products.
- Versatility: The physical properties of PAM can be altered by changing the polymerisation process. This means that by varying the degree of polymerisation or crosslinking, PAM can be tailored to specific needs, resulting in diverse forms and uses.
Polyacrylamide has found extensive use in several sectors due to its unique properties. Some of its primary applications are:
- Waste Water Treatment: PAM is often used as a flocculating agent in wastewater treatment. By binding to suspended particles, it allows them to aggregate and settle, facilitating their removal.
- Soil Conditioner: In agriculture, PAM is used to reduce soil erosion and improve water retention in irrigated lands.
- Recovery (EOR) techniques. It helps increase oil production by improving the displacement efficiency and reducing the water production.
- Cosmetics Industry: Thanks to its gel-forming property, PAM is used in various cosmetic and personal care products. It acts as a thickening agent and can retain moisture, making it an essential component in products like moisturizers, lotions, and hair styling products.
- Papermaking: In the paper industry, PAM is used as a retention and drainage aid, enhancing the efficiency of papermaking by improving the retention of fillers, fibers, and other materials used in the paper matrix.
Safety Concerns and Regulations
While polyacrylamide has a wide range of beneficial uses, it’s important to understand potential safety concerns associated with it. The primary concern is that unreacted acrylamide monomers, which can potentially be present in polyacrylamide, are neurotoxic and have been classified as probable human carcinogens. However, polyacrylamide itself is considered safe and non-toxic when properly handled and processed.
Regulations are in place in many countries to ensure that the amount of residual acrylamide in polyacrylamide is kept to a minimum. In the United States, for instance, the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA) have set standards and guidelines for the permissible levels of acrylamide in different products and applications.
Conclusion
In conclusion, polyacrylamide (PAM) is an immensely versatile polymer that has found extensive use in various industries, thanks to its unique properties like high water solubility, ability to form gels, and the ease of tailoring its physical properties. Whether in wastewater treatment, agriculture, oil recovery, cosmetics, or papermaking, PAM proves to be a crucial component. Despite potential safety concerns surrounding residual acrylamide, appropriate handling and processing ensure its safe usage. As science and technology continue to advance, there’s no doubt that new and exciting applications for polyacrylamide will be discovered, furthering its significance in many sectors.
quote: https://www.sciencedirect.com/topics/chemistry/polyacrylamide
https://www.britannica.com/science/polyacrylamide