Sodium polyacrylate
[CAS# 9003-04-7]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic sodium
• Name: Sodium polyacrylate
• Synonyms: Polyacrylic acid sodium salt; Poly(sodium acrylate); Propenoic acid homopolymer sodium salt; PAAS
• Molecular Formula: (C₃H₃NaO₂)_n
• Molecular Weight: ~5100
• CAS Registry Number: 9003-04-7
• EC Number: 692-137-3
• SMILES: C=CC(=O)[O-].[Na+]

Properties

• Density: 0.55 g/mL (25 ºC)

Safety Data

• Hazard Symbols: GHS07;GHS09 Warning
• Hazard Statements: H315-H319-H400-H410-H411
• Precautionary Statements: P264-P264+P265-P273-P280-P302+P352-P305+P351+P338-P321-P332+P317-P337+P317-P362+P364-P391-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319

Discovory and Applicatios

Sodium polyacrylate is a superabsorbent polymer (SAP) that has gained wide recognition for its exceptional ability to absorb and retain large quantities of water relative to its mass. The polymer is formed by the neutralization of polyacrylic acid with sodium hydroxide, resulting in a sodium salt of polyacrylic acid. Sodium polyacrylate is used extensively in a variety of industries, particularly in hygiene products, agriculture, and water management. Its development and applications represent significant advancements in polymer science, especially in areas where high water absorption and retention are critical.

The discovery and development of sodium polyacrylate as a superabsorbent polymer can be traced back to the 1960s and 1970s when researchers were exploring new materials that could replace conventional absorbents such as cotton and paper in hygiene products. The U.S. Department of Agriculture (USDA) first developed early versions of superabsorbent polymers for use in soil moisture retention. Over time, the commercial potential of sodium polyacrylate in various sectors was realized, leading to its widespread adoption.

One of the most prominent applications of sodium polyacrylate is in the production of disposable diapers, adult incontinence products, and feminine hygiene products. These products rely on the polymer’s ability to absorb and trap moisture, keeping the surface dry while minimizing leakage. Sodium polyacrylate can absorb several hundred times its weight in water, swelling into a gel-like substance that locks in the liquid. This capability makes it ideal for personal care products, where moisture management is essential for both comfort and hygiene.

Beyond hygiene products, sodium polyacrylate is also used in agriculture, particularly in the formulation of water-retaining gels and soil conditioners. In arid and drought-prone regions, the polymer is employed to retain moisture in the soil, helping plants to survive periods of water scarcity. Sodium polyacrylate is mixed into the soil, where it absorbs and holds water that is slowly released to the plant roots over time. This water-conservation technology improves the efficiency of irrigation and enhances crop yields, making it an important tool in sustainable agriculture.

Sodium polyacrylate also finds applications in the field of water management. It is used in products designed for flood control and emergency water containment. For example, in flood barriers or absorbent pads, the polymer's ability to absorb large amounts of water in a short period makes it effective for preventing water damage or containing spills. Additionally, sodium polyacrylate is used in disposable items like absorbent pads for medical use, where controlling the spread of fluids is crucial.

In industrial settings, sodium polyacrylate plays a role in moisture control and packaging. It is used in packaging materials to keep products dry by absorbing moisture from the air, thus protecting items such as electronics and food from humidity. Its ability to maintain dryness in closed environments is also exploited in desiccants, where the polymer serves as a non-toxic and efficient alternative to silica gel.

Another important application of sodium polyacrylate is in waste management, particularly in solidifying liquid waste. The polymer is used to treat hazardous liquids by converting them into a solid form, making them easier and safer to transport and dispose of. This process is especially useful in the disposal of industrial and medical waste, where managing liquid contaminants is a major challenge.

Research into sodium polyacrylate continues, with a focus on improving its environmental impact and expanding its applications. One challenge with sodium polyacrylate is its slow biodegradation rate, which has led to concerns about its environmental persistence. Efforts to develop biodegradable versions of superabsorbent polymers are ongoing, aimed at reducing the ecological footprint of disposable products while maintaining their performance.

In conclusion, sodium polyacrylate has revolutionized industries that require materials with high water-absorbing capacities. Its discovery has led to advancements in hygiene, agriculture, water management, and waste disposal, demonstrating its versatility and effectiveness as a superabsorbent polymer. As research continues, sodium polyacrylate and its derivatives are expected to play an increasingly important role in both commercial and environmental applications.

References

2011. Gel swelling theories: the classical formalism and recent approaches. Soft Matter, 7(22).
DOI: 10.1039/c1sm06031g

2011. Composite polymer hydrogels as draw agents in forward osmosis and solar dewatering. Soft Matter, 7(21).
DOI: 10.1039/c1sm06043k

2008. Creasing instability of surface-attached hydrogels. Soft Matter, 4(3).
DOI: 10.1039/b713263h