Journal of Textile and Clothing Science ISSN: 2581-561X (Online)

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REVIEW SUPER ABSORBENT : A DIMINUTIVE REVIEW Madhuja Manoj Katkar Institute of Chemical Technology, Mumbai, India

A R T I C L E I N F O A B S T R A C T

Article history: Super absorbency is superior swelling abilities originate to Received 02 February 2019 absorb and retain large amounts of aqueous solutions. Super- Received in revised form 23 absorbent polymers are cross-linked networks of hydrophilic February 2019 chains. With today’s demand for one-click solution, the Accepted 15 March 2019 development of superabsorbent technology has been largely 28/03/2019-Mar Keywords: directed by the needs of disposable hygiene segment, agriculture Absorbent, Agriculture, industry etc. Over the years, starch-grafted superabsorbent Industrial, Medical, Polymer, polymer turned into cross-linked acrylic homopolymers. This paper discusses concept, mechanism and major application areas of superabsorbent.

1. Introduction dissolving in water [2]. water uptake potential A Polymer is a large molecule composed of these materials goes as high as 100,000% of of several repeating units. 3-D crosslinked its own weight in a short period of time [3]. network of polymer molecules forms polymer The maximum volume of superabsorbent gels. Superabsorbent polymer (SAP) is polymers covers the synthetic or chemically or physically cross-linked polymer petrochemical source and mostly gels. When water meets one of these chains, it and its sodium or potassium salts, and is drawn into the molecule by osmosis. Water acrylamide is used in the industrial rapidly migrates into the interior of the production of superabsorbent polymers. polymer network where it is stored. Type and Nevertheless, superabsorbent polymers degree of crosslinkers governability of the produced from proteins and polysaccharides superabsorbent polymer to absorb and retain like chitin, cellulose, starch, and natural gums large volumes of water and aqueous solutions. etc., are the greener alternatives [2]. [1] superabsorbent polymer, hydrogel, Super absorbent polymers are classified absorbent polymers, absorbent gels, super based on polymer type, crosslinking and type soakers, super slurpers, water gel are the few of absorbent, as follows in figure 1. Currently, other appellations for superabsorbent synthetic polymers, especially acrylic, are polymers. These polymers could swell in used for manufacturing of superabsorbent. water and retaining a significant fraction This is because of cost-effectiveness of the (>20%) of water within their structure, without * Corresponding author. E-mail: [email protected] 1 Journal of Textile and Clothing Science

Figure 1 Classification of Superabsorbent Polymers process and good absorption efficiency of hydration and the formation of hydrogen these superabsorbent. However, today’s bonds are two of these interactions. market is demanding for "greener" alternatives to replace these synthetics partially or fully. Carbohydrate polymers, polysaccharides, such as Chitin, cellulose, starch, and natural gums such as xanthan, guar and alginates are polymerized to arrive at the solution. These polysaccharides are the cheapest and most abundant, available, and renewable organic Figure 3 Polymer-Solvent Interaction [1] materials. Super absorbent polymers are 2. Mechanisms of Swelling in polymerized by one of the following Superabsorbent Polymers techniques [4], The polymer backbone in the 1. Bulk Polymerization superabsorbent polymer is hydrophilic i.e. 2. ‘water loving’ because it contains water loving 3. Inverse Suspension Polymerization carboxylic acid groups (–COOH) as shown in figure 2[1]. Bulk polymerization is the simplest technique with high concentration monomer and monomer-soluble initiators and it produces high molecular weight polymer with high purity. In solution copolymerization reactions, the ionic or neutral monomers are mixed with the multifunctional cross-linking agent while in inverse suspension polymerization, the monomer solution is dispersed in the non- solvent forming fine monomer droplets, which are stabilized by the addition of Figure 2 Structure of SAP [1] stabilizer. When water is added to superabsorbent polymer there is a polymer-solvent interaction of ions of a solute with molecules of a solvent i.e. COO- and Na+ ions attract the polar water molecules, as shown in figure 3, called as

2 Volume: 2 Issue: 1 | January-March 2019, www.jtcsonline.com Super Absorbent Polymers: A Diminutive Review 3. Evaluation Methods [2] 4. Applications of Superabsorbent Superabsorbents are evaluated for the Polymers following properties; In general, superabsorbent polymers are 1. Free-absorbency Capacity: This test indicates white sugar-like materials, started to be uptake of distilled water while the sample practically applied in sanitary products, now is freely swollen without any load on the they have been widely used not only for testing sample. Free absorbency capacity hygiene products such as disposable diapers is tested by either of the three methods viz; for children, etc., but also for water retaining Tea-bag Method, Centrifuge method and soil products for gardening, water stop materials for the civil engineering and sieve method. construction, sheets for raising seedling, fresh- 2. Absorbency Under Load: This test indicates keeping agents for food distribution fields, uptake of 0.9% NaCl solution while the materials for poultice etc. [5]. However, this testing sample is pressurized by some paper emphases major applications areas like loads, usually, specified to pressure 0.3, agriculture, industrial grade, and medical 0.6, or 0.9 psi. sector, specific towards wound dressing, 3. Wicking Capacity and Rate: Wicking diapers, and sanitary pads. properties of a superabsorbent polymer 4.1 Superabsorbents in Agriculture are evaluated by preparing filter paper In agriculture and agroforestry, Super cone with superabsorbent polymer at the Absorbent Polymers are used as soil water tip and holding it in a petri dish containing retention agent, seed coating, soil-less water, for a specified time. cultivation, artificial turf, etc. 4. Swelling Rate: Rate of swelling is evaluated Super Absorbent Polymers act as micro by the vortex method or swelling time water reservoirs at plant roots. They absorb profile test. natural and supplied water 400-500 times their 5. Swollen Gel Strength: The mechanical own weight and release it slowly on account strength or modulus of swollen of root capillary suction mechanism, thus superabsorbent polymers is evaluated by preventing water loss in soil by leaching and rotational rheometric to quantify the evaporation. Superabsorbent polymers form swollen gel strength of superabsorbent a consistent cyclic process of absorption and polymer materials. release of water; the water so released can 6. Soluble Fraction: The sol content, i.e. the provide optimum moisture for quick sum of all water-soluble is measured by germination and seedling maturation as extraction of the superabsorbent polymer shown in figure 4. sample in distilled water. 7. Residual Monomer: High-performance liquid chromatography (HPLC) is often taken as a preferred method to quantify the residual monomer. 8. Ionic Sensitivity: To achieve a comparative measure of the sensitivity of the superabsorbent polymer materials towards aqueous fluid, a dimensionless swelling factor is calculated measuring absorption in a given fluid and absorption in distilled water.

Figure 4 Working of SAP at Plant Roots [6]

Volume: 2 Issue: 1 | January-March 2019, www.jtcsonline.com 3 Journal of Textile and Clothing Science Thus, superabsorbent polymers can help when meets water and the bag will inflate in saving water and labor by reducing quickly. The comparatively low weight of irrigation frequency, help to overcome these bags facilitates easy storage and drought conditions and act as soil transportation. conditioners, prevent leaching in sandy soils, Super absorbent polymer for concrete, in runoffs in mountainous and sloping fields, a controlled way, significantly change their restore soil biota, reduce soil erosion by properties in response to an external stimulus. surface run-offs, fertilizer and pesticide When it is exposed to water, they swell, and leaching to groundwater, reduce cost of water when subsequently subjected to drying, they and irrigation and increases yields of crops [6]. reversibly shrink. These key properties can Because of the superabsorbent polymer actively be used in relation to concrete. coating, the seed emergence quickly and give plants an early, healthy start. It also exhibits strong and good disease resistance. Such superabsorbent polymer coated seeds are very useful to plants in a drought area.

Figure 6 Anti-flood Bag before and after Water Absorption [6] Super absorbent when used in fire extinguisher gel, a layer of gel adheres the surface. This gel, thus, contain water Figure 5 SAP Coated Seeds [6] invariably. And fire cannot, therefore, spread Application of superabsorbent polymers rapidly since it must overcome the quantity of in golf and lawn can require less water and water present in the gel. fertilizer, with faster, healthier grow of lawn 4.3 Superabsorbents in Medical Field and the green last longer. Thus, it can reduce The largest use of superabsorbent the cost of maintenance and causes less polymers is in personal hygiene products. pollution [6]. Superabsorbent polymers are primarily used 4.2 Industry Grade Applications as an absorbent for water and aqueous Superabsorbent polymers have numerous solutions for diapers, adult incontinence scopes in various applications such as products, feminine hygiene products, and Functional coatings, Fire extinguishing gel, similar applications as a replacement of Cooling material, Anti-flood bag, Additive in traditional absorbent materials such as cloth, concrete, Air fresher, Additives of cosmetics, cotton, paper wadding, and cellulose fibre. etc. Superabsorbent polymer for diaper owns To prevent water penetration, tape good permeability, strong absorptive consisting of superabsorbent polymer is capacity, and maintenance ability, with no wrapped around the cable to provide return infiltration phenomenon under a protection against damage and corrosive certain pressure. Superabsorbent polymer for effect of water. Such cables are used in shows fast suction of blood, waterproof tape and waterproof ointment for high absorption capacity, and good gel using optical fibre cables. strength and moisture resistance. The strong Superabsorbent polymer anti-flood bag absorption capacity and water retention can be a good alternative to than traditional ability in women`s sanitary napkin can keep sandbags. Superabsorbent anti-flood bag dry and comfortable. absorbs water completely in 3 to 5 minutes 4 Volume: 2 Issue: 1 | January-March 2019, www.jtcsonline.com Super Absorbent Polymers: A Diminutive Review Wound dressing with superabsorbent 5. Conclusion material consists of polymer-based core Superabsorbent polymers have shaped an absorbs extrudes from the wound for a longer eye-catching space in the perspective of super- time at a higher rate and are suitable as swelling behavior, chemistry, and crafting the dressing for pressure ulcers, venous leg ulcers, variety of end products, ranging from postoperative wounds. Another type of personal care products to agriculture. dressing used as a primary dressing for However, further research is necessary to dermal wounds like pressure ulcers, skin widen the application horizon of tears, burns etc., intends to maintain a moist superabsorbent polymers. Especially, for environment and thus, enhances healing and environmental sustainability, the prevents wound desiccation promoting superabsorbent polymer prepared from autolytic debridement of a dry wound. natural resources would greatly increase its potential in various products.

6. References [1] Superabsorbent Polymers, Mark Elliott, http://chimianet.zefat.ac.il (accessed on 1 January 2019). [2] Superabsorbent Polymer Materials: A Review, https://www.researchgate.net/publication/242 582443 (accessed on 22 January 2019). [3] Applications of Super Absorbent Polymers in Agriculture, http://vikaspedia.in/agriculture/crop- production (accessed on 26 January 2019). Figure 7 Diaper with SAP [4] Absorbent Fibres, https://nptel.ac.in/courses/Absorbent Fibres To maintain the dry atmosphere in (accessed on 11 January 2019). operation theatres, polymeric textile [5] Super absorbent polymer and preparation consisting sheath of cellulose and method thereof, US 2016/0030921 A1 superabsorbent polymer absorbs and retains (accessed on 21 January 2019). [6] Super Absorbent Polymer, the liquids coming in contact. https://www.socochem.com (accessed on 28 January 2019).

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