Superabsorbent polymer

Last updated
Superabsorbent polymer powder Superabsorbent Polymer.jpg
Superabsorbent polymer powder

A superabsorbent polymer (SAP) (also called slush powder) is a water-absorbing hydrophilic homopolymers or copolymers [1] that can absorb and retain extremely large amounts of a liquid relative to its own mass. [2]

Contents


Water-absorbing polymers, which are classified as hydrogels when mixed, [3] 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. In deionized and distilled water, a SAP may absorb 300 times its weight [4] (from 30 to 60 times its own volume) and can become up to 99.9% liquid, and when put into a 0.9% saline solution the absorbency drops to approximately 50 times its weight.[ citation needed ] The presence of valence cations in the solution impedes the polymer's ability to bond with the water molecule.

The SAP's total absorbency and swelling capacity are controlled by the type 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. High cross-link density polymers exhibit lower absorbent capacity and swell, and the gel strength is firmer and can maintain particle shape even under modest pressure.

IUPAC definition for superabsorbent polymer IUPAC definition for a superabsorbent polymer.png
IUPAC definition for superabsorbent polymer

Superabsorbent polymers are crosslinked in order to avoid dissolution. There are three main classes of SAPs:

1.   Cross‐linked polyacrylates and polyacrylamides

2.   Cellulose‐ or starch‐acrylonitrile graft copolymers

3.   Cross‐linked maleic anhydride copolymers [1]

The largest use of SAPs is found in personal disposable hygiene products, such as baby diapers, adult diapers and sanitary napkins. [5] SAPs were discontinued from use in tampons due to 1980s concern over a link with toxic shock syndrome.[ citation needed ] SAPs are also used for blocking water penetration in underground power or communications cable, in self-healing concrete, [6] [7] horticultural water retention agents, control of spill and waste aqueous fluid, and artificial snow for motion picture and stage production. The first commercial use was in 1978 for use in feminine napkins in Japan and disposable bed liners for nursing home patients in the USA. Early applications in the US market were with small regional diaper manufacturers as well as Kimberly Clark. [8]

History

Until the 1920s, water-absorbing materials were fiber-based products. Choices were tissue paper, cotton, sponge, and fluff pulp. The water-absorbing capacity of these types of materials is only up to eleven times their weight and most of it is lost under moderate pressure.

In the early 1960s, the United States Department of Agriculture (USDA) was conducting work on materials to improve water conservation in soils. They developed a resin based on the grafting of acrylonitrile polymer onto the backbone of starch molecules (i.e. starch-grafting). The hydrolyzed product of the hydrolysis of this starch-acrylonitrile co-polymer gave water absorption greater than 400 times its weight. Also, the gel did not release liquid water the way that fiber-based absorbents do.

The polymer came to be known as “Super Slurper”. [9] The USDA gave the technical know-how to several US companies for further development of the basic technology. A wide range of grafting combinations were attempted including work with acrylic acid, acrylamide and polyvinyl alcohol (PVA).

Today's research has proved the ability of natural materials, e.g. polysaccharides and proteins, to perform super absorbent properties in pure water and saline solution (0.9%wt.) within the same range as synthetic polyacrylates do in current applications. [10] Soy protein/poly(acrylic acid) superabsorbent polymers with good mechanical strength have been prepared. [11] Polyacrylate/polyacrylamide copolymers were originally designed for use in conditions with high electrolyte/mineral content and a need for long term stability including numerous wet/dry cycles. Uses include agricultural and horticultural. With the added strength of the acrylamide monomer, used as medical spill control, wire and cable water blocking.

Copolymer chemistry

Superabsorbent polymers are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a poly-acrylic acid sodium salt (sometimes referred to as sodium polyacrylate). This polymer is the most common type of SAP made in the world today. According to the U.S. Food & Drug Administration, sodium polyacrylate is listed in Food Additive Status List, and there are strict limitations. [12] [ clarification needed ]

Other materials are also used to make a superabsorbent polymer, such as polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxymethylcellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, and starch grafted copolymer of polyacrylonitrile to name a few. The latter is one of the oldest SAP forms created.[ citation needed ]

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.

Gel polymerization

Hydrogel Superabsorber Hydrogel KSG 2917 pK.jpg
Hydrogel

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 resulting "logs" are sticky gels containing 60 to 70% water. The logs are shredded or ground and placed in various types of driers. Additional cross-linking agents may be sprayed on the particles' surface; this "surface cross-linking" 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 screened for proper particle size distribution and packaging. The gel polymerization (GP) method is currently[ when? ] the most popular method for making the sodium polyacrylate superabsorbent polymers now used in baby diapers and other disposable hygienic articles.

Solution polymerization

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 or saturate most substrates. 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 reactant polymer gel is then chopped, dried and ground to its final granule size. Any treatments to enhance performance characteristics of the SAP are usually accomplished after the final granule size is created.

Suspension polymerization

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. Performance enhancements can also be made during, or just after, the reaction stage.

Aviation

On 13 April 2010, Cathay Pacific flight 780 from Surabaya to Hong Kong encountered a dual engine stall descending whilst descending into Hong Kong International Airport, the aircraft landed safely with no fatalities. The investigation concluded that superabsorbent polymer (SAP) spheres, a component of a fuel filter monitor installed in a fueling dispenser at Juanda International Airport caused the main metering valves in the fuel metering unit to seize. It was discovered that salt water had contaminated the fuel supply at Juanda International Airport, which led to damage of the filter monitors and release of SAP spheres into the aircraft's fuel, eventually entering the main fuel supply lines. [13]

Uses

Expanded polymer balls Balls.jpeg
Expanded polymer balls

See also

Citations

  1. 1 2 Hawaii Energy and Environmental Technologies (HEET) Initiative. July 2016.
  2. ↑ Horie, K, et al., 890.
  3. ↑ Kabiri, K. (2003). "Synthesis of fast-swelling superabsorbent hydrogels: effect of crosslinker type and concentration on porosity and absorption rate". European Polymer Journal. 39 (7): 1341–1348. Bibcode:2003EurPJ..39.1341K. doi:10.1016/S0014-3057(02)00391-9.
  4. ↑ Mignon, Arn; Vermeulen, Jolien; Snoeck, Didier; Dubruel, Peter; Van Vlierberghe, Sandra; De Belie, Nele (2017-10-28). "Mechanical and self-healing properties of cementitious materials with pH-responsive semi-synthetic superabsorbent polymers". Materials and Structures. 50 (6): 238. doi:10.1617/s11527-017-1109-4. ISSN   1871-6873. S2CID   255318116.
  5. ↑ Sun, Fang; Messner, Bernfried A. (December 5, 2006), Manufacture of web superabsorbent polymer and fiber, archived from the original on August 29, 2011
  6. ↑ Snoeck, Didier; Van Tittelboom, Kim; Steuperaert, Stijn; Dubruel, Peter; De Belie, Nele (2012-03-15). "Self-healing cementitious materials by the combination of microfibres and superabsorbent polymers". Journal of Intelligent Material Systems and Structures. 25: 13–24. doi:10.1177/1045389X12438623. hdl: 1854/LU-6869809 . S2CID   92983639.
  7. ↑ Mignon, Arn; Devisscher, Dries; Graulus, Geert-Jan; Stubbe, Birgit; Martins, José; Dubruel, Peter; De Belie, Nele; Van Vlierberghe, Sandra (2017-01-02). "Combinatory approach of methacrylated alginate and acid monomers for concrete applications". Carbohydrate Polymers. 155: 448–455. doi:10.1016/j.carbpol.2016.08.102. hdl: 1942/22766 . ISSN   0144-8617. PMID   27702534. S2CID   46760339.
  8. ↑ Mulder, Douglas C.; O'Ryan, David E. (December 31, 1985), Method and apparatus for powder coating a moving web: US 4561380 A
  9. ↑ "SUPER SLURPER Compound with a super thirst". Agricultural Research: 7–9. June 1975.
  10. ↑ Zohuriaan-Mehr, M.J (2009). "Protein- and homo poly(amino acid)-based hydrogels with super-swelling properties". Polymers for Advanced Technologies. 20 (8): 655–671. doi:10.1002/pat.1395.
  11. ↑ Song, W., Xin, J., Zhang J. (2017). "One-pot synthesis of soy protein (SP)-poly (acrylic acid) (PAA) superabsorbent hydrogels via facile preparation of SP macromonomer". Industrial Crops and Products. 100: 117–125. doi:10.1016/j.indcrop.2017.02.018.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ↑ "Polymer Substances and Polymer Adjuvants for Food Treatment - 173.73 Sodium polyacrylate". U.S. Food and Drug Administration. Retrieved August 16, 2021.
  13. ↑ Report on the accident to Airbus A330-342 B-HLL operated by Cathay Pacific Airways Limited at Hong Kong International Airport, Hong Kong on 13 April 2010 (PDF) (Report). Civil Aviation Department The Government of Hong Kong Special Administrative Region. July 2013. Retrieved 10 Oct 2023.
  14. ↑ Jensen, Ole Mejlhede (2013). "Use of superabsorbent polymers in concrete" (PDF). Concrete International. 35 (1): 48–52.
  15. ↑ "水弹枪_百度图片搜索".
  16. ↑ Da Silva Jr., Macedo Carlos (January 31, 2008), ADHESIVE BANDAGE: United States Patent Application 20080027366
  17. ↑ "Food Additive Status List". U.S. Food & Drug Administration. 28 February 2024.
  18. ↑ "Safety of sodium polyacrylate, potassium polyacrylate". Socopolymer.

Related Research Articles

<span class="mw-page-title-main">Polyacrylamide gel electrophoresis</span> Analytical technique

Polyacrylamide gel electrophoresis (PAGE) is a technique widely used in biochemistry, forensic chemistry, genetics, molecular biology and biotechnology to separate biological macromolecules, usually proteins or nucleic acids, according to their electrophoretic mobility. Electrophoretic mobility is a function of the length, conformation, and charge of the molecule. Polyacrylamide gel electrophoresis is a powerful tool used to analyze RNA samples. When polyacrylamide gel is denatured after electrophoresis, it provides information on the sample composition of the RNA species.

<span class="mw-page-title-main">Polyacrylamide</span> Chemical compound

Polyacrylamide (abbreviated as PAM or pAAM) is a polymer with the formula (-CH2CHCONH2-). It has a linear-chain structure. PAM is highly water-absorbent, forming a soft gel when hydrated. In 2008, an estimated 750,000,000 kg were produced, mainly for water treatment and the paper and mineral industries.

<span class="mw-page-title-main">Acrylic acid</span> Chemical compound

Acrylic acid (IUPAC: propenoic acid) is an organic compound with the formula CH2=CHCOOH. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with water, alcohols, ethers, and chloroform. More than a million tons are produced annually.

A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility and sometimes its mechanics. In general usage, the term "soil conditioner" is often thought of as a subset of the category soil amendments, which more often is understood to include a wide range of fertilizers and non-organic materials. In the context of construction soil conditioning is also called soil stabilization.

<span class="mw-page-title-main">Sodium polyacrylate</span> Anionic polyelectrolyte polymer

Sodium polyacrylate (ACR, ASAP, or PAAS), also known as waterlock, is a sodium salt of polyacrylic acid with the chemical formula [−CH2−CH(CO2Na)−]n and has broad applications in consumer products. This super-absorbent polymer (SAP) has the ability to absorb 100 to 1000 times its mass in water. Sodium polyacrylate is an anionic polyelectrolyte with negatively charged carboxylic groups in the main chain. It is a polymer made up of chains of acrylate compounds. It contains sodium, which gives it the ability to absorb large amounts of water. When dissolved in water, it forms a thick and transparent solution due to the ionic interactions of the molecules. Sodium polyacrylate has many favorable mechanical properties. Some of these advantages include good mechanical stability, high heat resistance, and strong hydration. It has been used as an additive for food products including bread, juice, and ice cream.

<span class="mw-page-title-main">Acrylate polymer</span> Group of polymers prepared from acrylate monomers

An acrylate polymer is any of a group of polymers prepared from acrylate monomers. These plastics are noted for their transparency, resistance to breakage, and elasticity.

QPNC-PAGE, or QuantitativePreparativeNativeContinuousPolyacrylamideGel Electrophoresis, is a bioanalytical, one-dimensional, high-resolution and high-precision electrophoresis technique applied in biochemistry and bioinorganic chemistry to separate proteins quantitatively by isoelectric point and by continuous elution from a gel column.

Solution polymerization is a method of industrial polymerization. In this procedure, a monomer is dissolved in a non-reactive solvent that contains a catalyst or initiator.

<span class="mw-page-title-main">Polyacrylic acid</span> Anionic polyelectrolyte polymer

Poly(acrylic acid) (PAA; trade name Carbomer) is a polymer with the formula (CH2-CHCO2H)n. It is a derivative of acrylic acid (CH2=CHCO2H). In addition to the homopolymers, a variety of copolymers and crosslinked polymers, and partially deprotonated derivatives thereof are known and of commercial value. In a water solution at neutral pH, PAA is an anionic polymer, i.e., many of the side chains of PAA lose their protons and acquire a negative charge. Partially or wholly deprotonated PAAs are polyelectrolytes, with the ability to absorb and retain water and swell to many times their original volume. These properties – acid-base and water-attracting – are the bases of many applications.

Poly(N-isopropylacrylamide) (variously abbreviated PNIPA, PNIPAM, PNIPAAm, NIPA, PNIPAA or PNIPAm) is a temperature-responsive polymer that was first synthesized in the 1950s. It can be synthesized from N-isopropylacrylamide which is commercially available. It is synthesized via free-radical polymerization and is readily functionalized making it useful in a variety of applications.

<i>N</i>,<i>N</i>-Methylenebisacrylamide Chemical compound, polyacrylamide crosslinker

N,N′-Methylenebisacrylamide (MBAm or MBAA, colloquially "bis") is the organic compound with the formula CH2[NHC(O)CH=CH2]2. A colorless solid, this compound is a crosslinking agent in polyacrylamides, e.g., as used for SDS-PAGE.

<span class="mw-page-title-main">Expandable water toy</span> Type of toy made from superabsorbent polymers

Expandable water toys are novelty items made from a superabsorbent polymer. They are toys that expand after putting them into water for anything between a few hours up to several days, depending on size. They shrink in saltwater or when exposed to air. They are made from polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass.

<span class="mw-page-title-main">2-Acrylamido-2-methylpropane sulfonic acid</span> Chemical compound

2-Acrylamido-2-methylpropane sulfonic acid (AMPS) was a Trademark name by The Lubrizol Corporation. It is a reactive, hydrophilic, sulfonic acid acrylic monomer used to alter the chemical properties of wide variety of anionic polymers. In the 1970s, the earliest patents using this monomer were filed for acrylic fiber manufacturing. Today, there are over several thousands patents and publications involving use of AMPS in many areas including water treatment, oil field, construction chemicals, hydrogels for medical applications, personal care products, emulsion coatings, adhesives, and rheology modifiers.

<span class="mw-page-title-main">Water crystal gel</span> Water-absorbing polymer

Water crystal gel or water beads or gel beads is any gel which absorbs and contains a large amount of water. Water gel is usually in spherical form and composed of a water-absorbing superabsorbent polymer such as a polyacrylamide.

Xploderz is a line of toy weapons made by The Maya Group to compete with Hasbro's Nerf Super Soaker line and marketed as a safer alternative to paintball. The concept is based on Orbeez, a toy line also by The Maya Group that uses water-absorbent gel pellets, and hence the toy line is sometimes referred to as "Orbeez ball shooters".

Common hydrogel agriculture's ingredient is potassium polyacrylate or sodium polyacrylate. As a superabsorbent material, it can absorb plenty of water and turn water to gel to store water.

1-Vinylimidazole is a water-soluble basic monomer that forms quaternizable homopolymers by free-radical polymerization with a variety of vinyl and acrylic monomers. The products are functional copolymers, which are used as oil field chemicals and as cosmetic auxiliaries. 1-Vinylimidazole acts as a reactive diluent in UV lacquers, inks, and adhesives.

Dimethylaminoethyl acrylate or DMAEA is an unsaturated carboxylic acid ester having a tertiary amino group. It is a colorless to yellowish, water-miscible liquid with a pungent, amine-like odor. DMAEA is an important acrylic monomer that gives basic properties to copolymers.

<span class="mw-page-title-main">Hydrogel fiber</span>

Hydrogel fiber is a hydrogel made into a fibrous state, where its width is significantly smaller than its length. The hydrogel's specific surface area at fibrous form is larger than that of the bulk hydrogel, and its mechanical properties also changed accordingly. As a result of these changes, hydrogel fiber has a faster matter exchange rate and can be woven into different structures.

<span class="mw-page-title-main">Hydroxyethyl acrylate</span> Organic chemical-monomer

Hydroxyethyl acrylate is an organic chemical and an aliphatic compound. It has the formula C5H8O3 and the CAS Registry Number 818–61–1. It is REACH registered with an EU number of 212–454–9. It has dual functionality containing a polymerizable acrylic group and a terminal hydroxy group. It is used to make emulsion polymers along with other monomers and the resultant resins are used in coatings, sealants, adhesives and elastomers and other applications.

References

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.