Superabsorbent polymers (also called powder mud ) can absorb and store large amounts of the relative fluid to their own mass.
Water-absorbing polymers, which are classified as hydrogels when connected, absorb aqueous solutions through hydrogen bonds with water molecules. The ability of SAP to absorb water depends on the ion concentration of the aqueous solution. In deionized and distilled water, SAP can absorb 300 times its weight (from 30 to 60 times its own volume) and can be up to 99.9% of the liquid, but when incorporated into a 0.9% salt solution, absorption drops to about 50 times folding. its weight. The presence of valence cations in the solution inhibits the ability of the polymer to bind to water molecules.
Total absorption and swelling capacity are controlled by the type and level of cross-linker used to make the gel. Low-density cross-linked SAPs generally have a higher absorbency capacity and swell to a greater extent. This SAP type also has a softer and more sticky gel formation. High cross-link density polymers exhibit lower absorption capacity and swell, but gel strength is stronger and can maintain particle shape even under moderate pressure.
The largest use of SAPs is found in disposable personal hygiene products, such as baby diapers, adult protective clothing and sanitary napkins. SAP was discontinued from the use of tampons due to concerns in 1980 over the association with toxic shock syndrome. SAP is also used to block penetration of water in underground forces or communications cables, horticultural water retention agents, spill control and aqueous liquid waste, and artificial snow for film and stage production. The first commercial use was in 1978 for use in Japanese feminine napkins and disposable beds for nursing home patients in the United States. Initial applications in the US market are with small regional diaper manufacturers as well as Kimberly Clark.
Video Superabsorbent polymer
Histori
Until 1920, water-absorbing materials were cellulose or fiber-based products. The options are tissue paper, cotton, sponge, and pulp. The water absorbent capacity of this type of material only reaches 11 times its weight, but most are lost under moderate stress.
In the early 1960s, the United States Department of Agriculture (USDA) was working on materials to improve water conservation on the ground. They develop resins based on grafting of acrylonitrile polymers into the backbone of starch molecules (ie starch-grafting). The hydrolysed product of the hydrolysis of the acrylonitrile acrylic polymer provides a water absorption of more than 400 times its weight. Also, the gel does not release liquid water as did fiber-based absorbents.
Polymers came to be known as "Super Slurper". USDA provides technical knowledge to several US companies for further development of basic technology. Various combinations of grafting are tried including working with acrylic acid, acrylamide and polyvinyl alcohol (PVA). Today's research has proven the ability of natural materials, eg Polysaccharides and Proteins, to perform super absorbing properties in pure water and saline solution (0.9 wt%) in the same range as synthetic polyacrylates do in current applications. Soy protein/poly (acrylic acid) superabsorbent polymers with good mechanical strength have been prepared. Polyacrylate/polyacrylamide copolymers were originally designed to be used in conditions with high electrolyte/mineral content and the need for long-term stability including many wet/dry cycles. Use includes agriculture and horticulture. With the added strength of the acrylamide monomer, it is used as a medical spill control, wire & amp; blocking water cable
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The superabsorbent polymer is now generally made of acrylic acid polymerization mixed with sodium hydroxide in the presence of an initiator to form a sodium salt of poly-acrylic acid (sometimes referred to as sodium polyacrylate). This polymer is the most common type of SAP made in the world today.
Other ingredients are also used for preparing superabsorbent polymers, such as polyacrylamide copolymers, ethylene maleic anhydride copolymers, hydroxyl carboxyene cloosphs, polyvinyl alcohol copolymers, crosslinked polyethylene oxide, and polyacrylonitrile starch polymers for various names. The latter is one of the oldest SAP forms created.
Currently superabsorbent polymers are made using one of three main methods: gel polymerization, suspension polymerization or solution polymerization. Each process has its own advantages but all produce consistent product quality.
Gel polymerization
Acrylic acid mixtures, water, crosslinking agents and UV initiator chemicals are mixed and placed on moving belts or in large tubs. The liquid mixture then enters the "reactor" which is a long space with a series of powerful UV lamps. UV radiation promotes polymerization and cross reaction reactions. The resulting "log" is a sticky gel containing 60-70% water. The wood is grated or ground and placed in various types of dryers. Additional crosslinking agents may be sprayed onto the surface of the particles; This "cross-link" relationship increases the product's ability to swell under pressure - a property measured as Absorbency Under Load (AUL) or Absorbency Against Pressure (AAP). The dried polymer particles are then filtered for appropriate particle size distribution and packaging. The current gel polymerization (GP) method is the most popular method for making polymer sodium superabsorbent polymers now used in baby diapers and other disposable hygienic items.
Polymerization solution
The polymer solution offers the uptake of the granular polymer provided in solution form. Solutions can be diluted with water before application, and can coat most of the substrate or be used to dry it. After drying at a certain temperature for a certain time, the result is a coated substrate with superabsorbence. For example, this chemical can be applied directly to wires and cables, although this is mainly optimized for use on components such as rolled articles or sheet substrates.
Solvent-based polymerization is commonly used today for the manufacture of SAP co-polymers, especially those containing toxic acrylamide monomers. This process is efficient and generally has a lower capital cost base. The solution process uses a water-based monomer solution to produce gel reactant polymerized mass. Exothermic polymerization reaction energy itself is used to encourage many processes, helping to reduce production costs. The reactant polymer gel is then chopped, dried and ground to the ultimate granule size. Each treatment to improve SAP performance characteristics is usually resolved after the final granule size is made.
Suspension polymerization
The suspension process is practiced by only a few companies as it requires a higher level of production control and product engineering during the polymerization step. This process delays a water-based reactant in a hydrocarbon-based solvent. The end result is that the suspension polymerization creates primary polymer particles in the reactor rather than mechanically in the post-reaction stage. Performance improvements can also be made during or after, the reaction stage.
Maps Superabsorbent polymer
Usage
- Waterball/Crystalball Arms (a cross between paintball and airsoft; used in China)
See also
- Sodium polyacrylate
- Potassium polyacrylate
Quote
References
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K. Horie; M. BÃÆ'¡ron; R. B. Fox; J. He; M. Hess; J. Kahovec; T. Kitayama; P. Kubisa; E. MarÃÆ' Â © chal; W. Mormann; R. F. T. Stepto; D. Tabak; J. Vohldal; E. S. Wilks & amp; W. J. Work (2004). "Definitions of terms relating to polymer reactions and functional polymeric materials (IUPAC Recommendations 2003)" (PDF) . Pure and Applied Chemistry . 76 (4): 889-906. doi: 10.1351/pac200476040889. - Katime Trabanca, Daniel; Katime Trabanca, Oscar; Katime Amashta, Issa Antonio (September 2004). Los Angeleses inteligentes de este milenio: Los hidrogeles macromoleculares. SÃ © ntesis, supporting y aplicaciones (1 ed.). Bilbao: Editorial Servicio de la Universidad del PaÃÆ's Vasco (UPV/EHU). ISBN: 84-8373-637-3.
- Buchholz, Fredric L; Graham, Andrew T, eds. (1997). Modern Technology Superabsorbent Polymer (1 ed.). John Wiley & amp; Children. ISBNÃ, 0-471-19411-5.
External links
- Nonwoven Contains Super Immobilized Absorbable Polymeric Particles
Source of the article : Wikipedia
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