1. Basic Definition

Polyacrylic Acid (PAA)

• Acid form of the polymer
• Chaical form: –[CH₂–CH(COOH)]–ₙ
• Contains carboxylic acid groups (COOH)

Sodium Polyacrylate (Na-PAA or PAAS)

• Neutralized salt form of PAA
• Chaical form: –[CH₂–CH(COO⁻Na⁺)]–ₙ
• Carboxylic groups are replaced by sodium carboxylate (COO⁻Na⁺)

2. Solubility & Water Behavior

PAA

• Soluble in water only at higher pH
• In acidic pH, it is less ionized → low swelling
• Forms viscous solutions after neutralization

Sodium Polyacrylate

• Highly water-soluble
• Extraely water-absorbing / superabsorbent
• Swells to form large hydrogels
• Can absorb several hundred times its weight in water

3. pH Sensitivity

Polyacrylic Acid

• pH-responsive polymer
• Thickens dramatically after neutralization
• Behavior changes h3ly with pH

Sodium Polyacrylate

• Already neutralized
• More stable across pH ranges
• Swelling decreases in high-salt environments (salt-sensitive)

4. Applications

Polyacrylic Acid (PAA)

Used for:

• Detergent dispersants
• Thickening agents
• Water-treatment scale inhibitor
• Adhesives / coatings
• Cosmetics (when neutralized, e.g., carbomer-like use)

Sodium Polyacrylate

Used for:

• Superabsorbents (diapers, sanitary pads)
• Water-retention gels for agriculture
• Leak-proof gels in medical absorbents
• Thickening agents in some detergents
• Sludge dewatering

5. Physical Properties

6. Which to Use?

Choose Polyacrylic Acid when:

✔ You need dispersing, scale inhibition, viscosity control, or pH-responsive behavior
✔ Applications in detergents, coatings, water treatment, cosmetics

Choose Sodium Polyacrylate when:

✔ You need superabsorbent properties
✔ Applications in diapers, agriculture water gels, spill absorbents

Differences between PAA and sodium polyacrylate