Food grade industrial grade 98% Sodium polyacrylate CAS 9003-04-7

What is sodium polyacrylate? How does it work?

Sodium polyacrylate, also known as sodium polyacrylate, is a high molecular weight polymer of sodium acrylate, represented by the chemical formula (C3H3NaO2)n, with CAS number 9003-04-7. It is a white powder or granules that dissolves in water to form a highly viscous solution. Its molecular weight varies, with properties differing accordingly—low molecular weight grades are highly effective dispersants and scale inhibitors, while ultra-high molecular weight grades are superabsorbent resins capable of absorbing hundreds of times their own weight in water. Industrial-grade sodium polyacrylate, with its dispersing, thickening, flocculating, and ultra-high water absorption properties as anionic polyelectrolytes, is widely used in superabsorbent materials, water treatment, papermaking, coatings, agriculture, and detergents.

Basic information : Chinese name: Sodium polyacrylate; English name: Sodium polyacrylate (abbreviation: PAAS); CAS number: 9003-04-7; Molecular formula: (C3H3NaO2)n (repeating unit: sodium acrylate); Molecular weight: thousands to millions (depending on the degree of polymerization; low molecular weight grade is liquid, high molecular weight grade is solid powder); Appearance: white powder or granules, soluble in water to form a highly viscous liquid, aqueous solution pH: 6-9; Synonyms: Sodium 2-acrylate homopolymer, sodium polyacrylate, PAAS, etc.

Structurally , sodium polyacrylate is a linear polymer formed by the polymerization of sodium acrylate monomers. The main chain is a long chain connected by carbon-carbon single bonds, and each repeating unit has a sodium carboxylate group (-COONa) attached to its side. The structural unit is -CH2-CH(COONa)-. The sodium carboxylate group ionizes in water to release sodium ions, giving the molecular chain a large amount of negative charge. The repulsion of like charges allows the chain segments to fully extend .

physical properties , high molecular weight sodium polyacrylate is a white powder or granules, while low molecular weight sodium polyacrylate is a colorless to pale yellow viscous liquid; it is odorless and tasteless, and highly hygroscopic; it slowly dissolves in water to form an extremely viscous transparent liquid, and is insoluble in organic solvents such as ethanol; its density is approximately 1.32 g/cm³; it is heat-resistant and does not decompose when heated to approximately 300℃; its viscosity changes very little over long-term storage, and its properties are stable.

Chemically , sodium polyacrylate is an anionic polyelectrolyte: when dissolved in water, it ionizes into sodium ions and polyacrylate anions, and the molecular chain carries a large number of negative charges; it is easily affected by acids and metal ions—it can form insoluble salts and cross-link and gel when it encounters divalent or higher metal ions (such as calcium, magnesium, aluminum, and zinc), but it remains in solution when the amount of metal ions is small. Therefore, it can be used as a scale inhibitor and dispersant, and can also prevent the redeposition of dirt during washing; it is alkali-resistant and heat-resistant, and its viscosity increases under alkaline conditions. It is chemically stable and needs to be stored in a moisture-proof environment.

Why does sodium polyacrylate play these roles in industrial fields such as superabsorbent materials, water treatment, papermaking, coatings, and agriculture? Its mechanism of action mainly includes the following:

Anionic scale inhibition mechanism : Polyacrylate anions are adsorbed on the surface of microcrystals such as calcium carbonate and calcium sulfate, as well as silt particles. The repulsion of like charges prevents crystal growth and particle aggregation and deposition, thus stably dispersing scale ions and suspended matter in water—this is the basis for its use as a scale inhibitor and dispersant.

Superabsorbent polymer (SAP) network mechanism : Slightly cross-linked sodium polyacrylate forms a three-dimensional network. The osmotic pressure generated by the ionization of sodium carboxylate groups draws water into the network and locks it in by hydrogen bonds. It can absorb and retain hundreds of times its own weight in water—this is the core of the application of superabsorbent polymers.

Polymer flocculation bridging mechanism : Long chains of sodium polyacrylate with a molecular weight of up to millions can simultaneously adsorb multiple suspended particles, bridging the particles and causing the fine particles to aggregate and settle—this is the basis for its use as a flocculant in solid-liquid separation and wastewater treatment.

Thickening and water-retaining mechanism : Sodium polyacrylate with a molecular weight of over 100,000 dissolves in water to form a high-viscosity solution, which increases the viscosity of coatings, latexes and other systems, making it difficult for water to separate out and keeping the system uniform and stable—this is the basis for its use as a coating thickener and water-retaining agent.

Chelating anti-redeposition mechanism : Polyacrylate ions can chelate calcium and magnesium ions in water and encapsulate washed-off dirt particles to prevent dirt from redepositing onto the fabric surface—this is the basis for its use as an auxiliary agent in detergents.

All Uses of Industrial Grade Sodium Polyacrylate

1. Field of superabsorbent materials

Superabsorbent polymer for diapers and sanitary napkins

Cross-linked sodium polyacrylate absorbs and locks in large amounts of liquid, making it the core material of absorbent cores in absorbent hygiene products.

Corresponding products: diapers, sanitary napkins, absorbent hygiene products, etc.

Absorbent pads and functional absorbent materials

Used for pet pee pads, absorbent food storage pads, and ice packs, etc.

Corresponding products: pet pee pads, nursing pads, absorbent ice packs, etc.

2. Water treatment field

Circulating cooling water scale inhibitor and dispersant

Prevent calcium carbonate and calcium sulfate scaling in circulating cooling water of power plants, chemical plants, fertilizer plants, oil refineries, and air conditioning systems.

Corresponding products: scale inhibitors for circulating water, cooling water treatment agents, etc.

Boiler water and water quality stabilizers

Low molecular weight grades are used as water quality stabilizers to control scaling and corrosion.

Corresponding products: water quality stabilizers, boiler water treatment agents, etc.

Wastewater treatment flocculants

Ultra-high molecular weight grade flocculants are used for solid-liquid separation of sewage and industrial wastewater.

Corresponding products: flocculants, wastewater treatment agents, etc.

3. Paper industry

Coated paper dispersant

Grades with a molecular weight of 2000-4000 are used as dispersants in paper coatings, maintaining good rheological properties and aging stability in high-concentration coatings.

Corresponding products: coatings for coated paper, coating slurries for art paper, etc.

4. Coatings and building materials industry

Latex paint thickeners and water-retaining agents

Grades with a molecular weight of over 100,000 increase the viscosity of coating systems such as carboxylated styrene-butadiene latex and acrylic emulsions, thus preventing water separation.

Corresponding products: latex paint, water-based coatings, architectural coatings, etc.

5. Agriculture

Soil conditioner and water-retaining agent

It absorbs and slowly releases water into the soil, reducing irrigation frequency and improving planting conditions in arid regions.

Corresponding products: soil water retention agents, drought-resistant water-retaining granules, horticultural water retention products, etc.

6. Detergent industry

Detergent

It chelates calcium and magnesium ions, prevents dirt redeposition, and improves the cleaning effect of detergents.

Corresponding products: laundry detergent, laundry liquid, washing aids, etc.

7. Textile printing and dyeing and ceramics industry

Textile printing and dyeing dispersants

Used for dispersing printing and dyeing pastes and pigments to maintain the uniformity of the system.

Corresponding products: dyeing and printing auxiliaries, sizing dispersants, etc.

ceramic and building material dispersants

Used for dispersing ceramic slurries, glazes and building material slurries, improving fluidity.

Corresponding products: ceramic slurry, glaze, building material dispersant, etc.

Summary

Sodium polyacrylate (CAS 9003-04-7) is a linear or slightly cross-linked polymer of sodium acrylate: a main chain with densely packed sodium carboxylate groups, allowing it to function as a scale inhibitor, dispersant, thickener, water-retaining agent, flocculant, and superabsorbent resin, depending on its molecular weight and degree of cross-linking. It's found in the absorbent cores of diapers, in the pipes of circulating cooling water systems, in the emulsions of wall paints, and in the formulations of laundry detergents—serving numerous industrial sectors such as hygiene products, water treatment, papermaking, coatings, agriculture, and detergents through its diverse capabilities as anionic polyelectrolytes. Understanding its molecular weight-function correspondence explains why it has become a versatile polymer material in industry.