Modern superabsorbent polymer technology pdf

Water-absorbing polymers, which are classified as hydrogels when cross-linked, absorb aqueous solutions through hydrogen bonding with water molecules. A SAP’s ability to absorb water depends on the ionic concentration of the aqueous solution. The total absorbency and swelling capacity are controlled by the modern superabsorbent polymer technology pdf and degree of cross-linkers used to make the gel. Low-density cross-linked SAPs generally have a higher absorbent capacity and swell to a larger degree.

These types of SAPs also have a softer and stickier gel formation. The largest use of SAPs is found in personal disposable hygiene products, such as baby diapers, adult protective underwear and sanitary napkins. Until the 1920s, water absorbing materials were cellulosic or fiber-based products. Choices were tissue paper, cotton, sponge, and fluff pulp. The water absorbent capacity of these types of materials is only up to 11 times their weight, but most of it is lost under moderate pressure.

The USDA gave the technical know-how to several USA companies for further development of the basic technology. This polymer is the most common type of SAP made in the world today. Today superabsorbent polymers are made using one of three primary methods: gel polymerization, suspension polymerization or solution polymerization. Each of the processes have their respective advantages but all yield a consistent quality of product. A mixture of acrylic acid, water, cross-linking agents and UV initiator chemicals are blended and placed either on a moving belt or in large tubs. The liquid mixture then goes into a “reactor” which is a long chamber with a series of strong UV lights.

The UV radiation drives the polymerization and cross-linking reactions. The logs are shredded or ground and placed in various sorts of driers. Solution polymers offer the absorbency of a granular polymer supplied in solution form. Solutions can be diluted with water prior to application, and can coat most substrates or used to saturate them. After drying at a specific temperature for a specific time, the result is a coated substrate with superabsorbency. For example, this chemistry can be applied directly onto wires and cables, though it is especially optimized for use on components such as rolled goods or sheeted substrates. Solution-based polymerization is commonly used today for SAP manufacture of co-polymers, particularly those with the toxic acrylamide monomer.

This process is efficient and generally has a lower capital cost base. The solution process uses a water-based monomer solution to produce a mass of reactant polymerized gel. The polymerization’s own exothermic reaction energy is used to drive much of the process, helping reduce manufacturing cost. The suspension process is practiced by only a few companies because it requires a higher degree of production control and product engineering during the polymerization step. This process suspends the water-based reactant in a hydrocarbon-based solvent. The net result is that the suspension polymerization creates the primary polymer particle in the reactor rather than mechanically in post-reaction stages. Synthesis of fast-swelling superabsorbent hydrogels: effect of crosslinker type and concentration on porosity and absorption rate”.

History of Super Absorbent Polymer Chemistry”. Crystal Soil For Plants and Flowers”. Archived from the original on April 2, 2016. Water Absorbent Pads for Meats, Fruits and Vegetables”. Los materiales inteligentes de este milenio: Los hidrogeles macromoleculares. This page was last edited on 3 April 2018, at 11:47.

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