Sodium Polyacrylate, 9003-04-7

Sodium Polyacrylate, 9003-04-7

1. Physical and Chemical Properties

• Chemical formula: [−CH2−CH(CO2Na)−]n

• Appearance: White powder or granules

• Density: ~1.22 g/cm³

• Solubility: Insoluble in water, but swells to form a hydrogel

• Key property: Superabsorbent polymer (SAP) capable of absorbing 100–1000 times its own weight in water

• Stability: Thermally stable, non-volatile, non-toxic in polymer form

2. Applications

• Hygiene products: Diapers, sanitary napkins, adult incontinence pads

• Agriculture: Soil conditioner and water retention agent

• Water treatment: Heavy metal ion removal and flocculation

• Construction: Crack prevention and water-proofing additives in concrete

• Food packaging: Moisture control in absorbent pads

• Cosmetics: Gel-based formulations for moisture retention

3. Other Names

• IUPAC name: Poly(sodium prop-2-enoate)

• Common abbreviations: PAAS, SAP, ACR

• Trade names: Waterlock, Super Absorbent Polymer

4. Sectoral Suitability Table

5. Why It Is Preferred

• Exceptional water absorption capacity compared to other polymers

• Cost-effective with small amounts delivering high performance

• Versatile across multiple industries

• Environmentally beneficial in agriculture (reduces irrigation needs)

• Stable and safe for consumer products

6. Types and Molecular Weight

• Forms:

  • Powder (industrial additives)

  • Granules (agriculture, hygiene)

  • Gel (cosmetics, specialty uses)

• Molecular weight:

  • Typically 2–5 million g/mol for superabsorbent applications

  • Lower molecular weights are used when higher solubility or viscosity control is required

7. Types and Molecular Weight 

Forms & Usage:

• Powder form (industrial additives):

  • Used in water treatment, coatings, adhesives.

  • Typical dosage: 0.05–0.5% of total formulation depending on viscosity and ion-binding needs.

  • Function: Acts as dispersant, scale inhibitor, and stabilizer.

• Granule form (agriculture, hygiene):

  • In diapers and sanitary pads: 2–5 g per unit ensures rapid absorption and retention.

  • In agriculture: 2–10 kg per hectare mixed into soil to improve water retention.

  • Function: Superabsorbent capacity, prevents leaching, keeps soil moist longer.

• Gel form (cosmetics, specialty uses):

  • Used in peel-off masks, creams, and gels.

  • Typical concentration: 0.1–1% depending on desired viscosity and film strength.

  • Function: Provides moisture retention, film formation, and smooth texture.

Molecular Weight Ranges:

• High molecular weight (2–5 million g/mol):

  • Best for superabsorbent applications (diapers, agriculture).

  • Provides strong gel strength and water retention.

• Medium molecular weight (500,000–2 million g/mol):

  • Used in water treatment and construction.

  • Balances solubility with dispersant properties.

• Low molecular weight (<500,000 g/mol):

  • Preferred in cosmetics and coatings where viscosity control and smooth film formation are critical.

  • Easier to disperse, less crosslinking, more flexible gels.

Functional Benefits by Type:

• Powder: Easy to dose, disperses quickly in industrial systems.

• Granules: Controlled swelling, ideal for hygiene and soil applications.

• Gel: Directly usable in formulations, provides immediate texture and moisture effects.

 In practice, the choice of type and molecular weight depends on the sector:

• Hygiene → High MW granules for maximum absorption.

• Agriculture → High MW granules for soil water retention.

• Water treatment → Medium MW powders for dispersant action.

• Cosmetics → Low to medium MW gels for smooth film-forming and viscosity control.