Highly Performing Polysaccharide Hydrogels can Replace Acrylic Acid-Based Superabsorbent Polymers in Sanitary Napkins

Abstract

Super absorbent polymers (SAPs) used in sanitary napkin are not required for water absorption capacity as high as in baby diapers and adult incontinence pads. Sanitary napkins must absorb menses, which is delivered at a significantly lower rate and overall daily amount than urines. Thus, the acrylic acid (AA) component can not be strictly necessary. By proper formulation design and processing, polysaccharide SAPs can be equally or even better performing than AA-containing SAPs in sanitary napkins. Fully biodegradable sodium alginate (SA)-based SAPs are prepared through ionic cross-linking by CaCl₂ and introduced in female pads. The optimal solution concentrations (SA 8% w/v, CaCl₂ 0.25% w/v in water) and reaction time are identified, and addition of cellulose nanocrystals (CNC) at different weight contents (0–3 w%) is tested. Morphology, physico-chemical properties, rheology, free swelling capacity (FSC), centrifuge retention capacity, and weight loss in soil are assessed. Increasing CNC content decreases FSC. Rheology results demonstrate higher storage and loss moduli for SA-based SAPs versus commercial SAPs. The superior SA-SAP developed is used in varying amounts for manufacturing sanitary napkin prototypes, revealing that excellent menstrual fluid absorption, surpassing commercial pads. Replacing AA-based with polysaccharide-based SAPs would reduce the environmental impact of hygienic product waste.