Superabsorbents water absorption capacity

The water-absorption capacity of superabsorbent polymers is usually measured by the following methods. The water-absorption capacity is greatly affected by not only the chemical structures of the polymers but also the external conditions such as kinds of solutions, temperature, pressure, etc. under which it is measured. 

The various effects on the water-absorption ability of the polymers were investigated with superabsorbent polymers having anionic or cationic groups. Several effects on the water-absorption capacity of the superabsorbent polymers having carboxyl groups(l) or phosphonium groups(4) are described in the following section. 

In recent years, it is reported that the water-absorption capacity of crosslinked poly(sodium aerylates) ean be increased by increasing the erosslinking density near the surface and by decreasing the crosshnking density at the inner side of superabsorbent copolymers. It is also reported that this type of superabsorbent polymer has high mechanical strength. 

Effect of physical structure of superabsorbent polymers on the water-absorption rate or water-absorption capacity... 

The water-absorption rate of usual superabsorbent polymers can be increased by increasing the temperature, but the water-absorption capacity after equilibrium at... 

Examples of applications of polyacrylamide-based nanocomposites refer mainly to improved superabsorbents with water absorption capacities higher than 1,000 g H20/g of solid [92]. Other uses of this type of material address the removal of pollutants, such as Pb(II) and Cu(II) [97, 99], methylene blue (Fig. 5), and other dyes [100]. Other examples related to environmental apphcations are reported in Sect. 4.2.2 as the nanocomposites may also incorporate biopolymers such as psyllium gum [101]. 

Dutkiewicz established a model to characterise the change in the void volume in the absorbent stmeture containing superabsorbent materials and also proposed a new testing method to measure the new defined fluid acquisition and storage efficiency, m which water absorbency is measured when a certain weight is placed uniformly on the surface of the swollen gel for a period of time, and the rate of fluid acquisition is measured under load of 2.8 kPa, three insults of 0.9% saline in 75 ml each. The water absorption capacity measurement under near-vacuum suction by using a Buchner funnel (equivalent to a pressure of 22.1 kPa) was also designed. " ... 

A prescribed amount of superabsorbent polymer is mixed with a prescribed amount of the desired aqueous solution, which is stirred by means of a magnetic stirring bar in a small beaker. As the water absorption proceeds, the viscosity of the suspension increases until the stirring vortex disappears at the sorption time, ty. The swelling capacity at equilibrium (Qmax) is calculated by using Eq. (2) ... 

The most important property of superabsorbent polymers is their ability to absorb water. Traditional water-absorbing materials such as cotton, pulp and sponges absorb water into interstices by capillary phenomenon. By contrast, superabsorbent polymer absorbs water into three-dimensional (3D) networks of a erosslinked polymer by the compatibility of polymer chains and water and by osmotic pressure. Hence, superabsorbent polymers laek absorption speed but have a much better water-absorption eapaeity eompared to cotton or pulp. Products that have a high water-absorption property include sanitary produets, such as disposable diapers, eonstmetion materials, mulch, water sealant for electric cables, freshness maintenance materials in the food industry. Of the sanitary products, of the disposable diaper is the best example of a product that has a high waterabsorbing capacity. The superabsorbent polymer is indispensable for disposable diapers, and it drastically improved the performance of disposable diapers. Here, the development and current status of disposable diapers, the structure of disposable diapers in which a superabsorbent polymer is incorporated, and advances in the development of superabsorbent polymers will be described. 

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