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OVERVIEW
Superabsorbent Polymer (SAP), also known as Superabsorbent Material (SAM), is prized across consumer and industrial markets for its remarkable water affinity—absorbing up to 500× its weight in aqueous solutions and locking it in permanently. Originally developed in the 1960s by the U.S. Department of Agriculture for soil water conservation (using starch-grafted acrylonitrile), modern SAP technology relies on crosslinked acrylic polymers neutralized with sodium for superior performance.

Since its debut in sanitary napkins in 1978 and baby diapers in 1982, SAP has become indispensable in hygiene products. Today, global production exceeds 3 million tons annually, primarily serving feminine hygiene pads, baby and adult diapers, and other incontinence applications.

SUPERABSORBENT CHEMISTRY

Formation of SAP

GELSAP™ superabsorbents are synthesized by reacting acrylic acid with sodium hydroxide and a cross-linker (e.g., TMPTA or tetraallyl ethoxy ethane), yielding a sodium polyacrylate network. Three principal polymerization methods are used:

1. Gel Polymerization

   • Process: Acrylic acid, NaOH, water, cross-linkers, and UV initiators are sprayed onto a moving belt under high-intensity UV lamps.

   • Result: A swollen “wet cake” that’s milled, dried, and optionally surface–cross linked to optimize absorbency, acquisition rate, and permeability.

2. Suspension Polymerization

   • Process: Monomers and additives are suspended in an organic solvent, forming crosslinked SAP beads.

   • Control: Reactor conditions (temperature, agitation, residence time) determine bead size. After filtration, drying, and optional surface-cross linking, beads are bulk packaged.

3. Solution Polymerization

   • Process: Acrylic acid and reagents dissolve in a non-reactive solvent, polymerizing into a liquid SAP solution.

   • Ứng dụng: Coated onto cellulose or nonwoven fibers and dried in-line to produce SAP-enhanced substrates for air-laid or laminate cores.

SAP ABSORPTION MECHANISM

• Osmotic Uptake: SAP particles behave like semipermeable membranes, drawing in water or bodily fluids and swelling into a gel.

• High Capacity: One gram of GELSAP™ can absorb hundreds of grams of pure water and retain it under moderate pressure—ideal for diapers and pads under body weight.

• Saline Effects: In high-salt fluids (urine, blood), absorption capacity decreases to tens of grams; GELSAP™ formulations are tailored via crosslink density to balance capacity and gel strength.

KEY PERFORMANCE CHARACTERISTICS

• Particle Size Distribution

• Free Swell Capacity (pure water)

• Absorption Under Load (water retention under pressure)

• Retention & Permeability

• Acquisition Rate

• Gel Strength & Deformation Resistance

• Wicking & Distribution

MAJOR SAP MANUFACTURERS & CAPACITIES

GELSAP™ APPLICATIONS

GELSAP™ leverages sodium polyacrylate’s exceptional fluid management to engineer custom absorbent cores for:

• Personal Hygiene: Ultra-thin laminates sandwiching SAP between tissue layers.

• Airlaid Cores: Blended SAP and cellulose fibers for high-capacity pads.

• Specialty Laminates: Water-retentive polyester or nonwoven substrates with adhesive-bonded SAP.

All GELSAP™ cores are produced in bulk rolls, slit or sheeted per customer specifications, in an ISO 9001:2015–certified facility.

From diapers and feminine care to wound dressings, medical packaging, and industrial spill control, GELSAP™ delivers tailored SAP solutions for any fluid-management challenge.