Superabsorbent Polymer (SAP)
Direct Answer
The superabsorbent polymer (SAP) is the workhorse of modern absorbent cores — a cross-linked sodium polyacrylate that swells into a gel, locking liquid away from skin so thin diapers and pads can hold many times their own weight.
Key Takeaways
- Superabsorbent polymer (SAP) is a cross-linked polymer, usually sodium polyacrylate, that absorbs and retains hundreds of times its own weight in liquid by swelling into a gel.
- Chemical type: Cross-linked sodium polyacrylate (typical)
- Absorption capacity: Roughly 300–500x its own weight in distilled water (typical)
- Absorption in saline: Roughly 30–60x its own weight in 0.9% saline (typical)
Material Properties
| Property | Typical Value | Note |
|---|---|---|
| Chemical type | Cross-linked sodium polyacrylate (typical) | Cross-linking prevents the polymer from dissolving; it swells instead |
| Absorption capacity | Roughly 300–500x its own weight in distilled water (typical) | Industry magnitude; exact values depend on polymer grade and test method |
| Absorption in saline | Roughly 30–60x its own weight in 0.9% saline (typical) | Saline ions reduce swelling vs pure water |
| Key performance metrics | CRC (Centrifuge Retention Capacity), AAP (Absorption Against Pressure), SFC (Saline Flow Conductivity) | The three standard quality parameters used to grade SAP in absorbent cores |
| Function | Locks liquid as a gel under pressure | Gel prevents rewet back to skin and allows thinner cores |
Applications
- Diaper absorbent cores
- Sanitary pad cores
- Adult incontinence products
- Wound dressings (medical SAP)
Key Manufacturers & Suppliers
- BASF (major global SAP producer)
- Evonik (major global SAP producer)
- Nippon Shokubai (major global SAP producer)
Supplier lists reflect commonly cited industry names, not endorsements. Always verify current supply arrangements directly.
Safety Notes
SAP in disposable hygiene products is a widely reviewed material; toxicological reviews generally consider it safe for skin contact in intended use. Keep the product dry and change it regularly — a saturated core is a hygiene risk regardless of material.