Development and Characterization of Sodium Alginate-Based Bio-hybrid Super Absorbent Polymer with High Retention Capacity Suitable for Baby Diapers

Due to their capacity of water absorption, super absorbent polymers (SAPs) are greatly requested in hygienic applications, thus representing large volume products needing for a good biodegradability. This study aims to develop new SAPs for baby diapers by combining sodium alginate (SA) and cellulose nanocrystals (CNC) with acrylic acid (AA). The effect of different AA/SA ratios and CNC concentrations in the presence of ammonium persulfate (APS) as an initiator, and N–N-methylene bis-acrylamide (NMBA) as a cross-linker is investigated. We assess morphological and physicochemical properties of the SAPs, as well as their absorption characteristics and rheological properties. The results show that SAPs with AA/SA weight ratio of 70:30 containing 2% w/w CNC have the highest water absorption capacity, i.e., 78.4 g/g in saline solution. These SAPs also demonstrate high retention capacity and better absorption capacity under load than other SAPs. We further optimize the formulation by increasing the neutralization degree of AA and reducing the solid content, reaching an absorption capacity in the salt solution up to 100.08 g/g. Finally, the absorbent core made with fewer amounts of SAPs and fluff pulp led to functional properties superior to those of commercial baby diapers. High polysaccharide content SAPs could contribute to improve diaper sustainability.