Biodegradable sodium lignosulfonate-based superabsorbent hydrogels for disposable hygiene products based on hyperbranched polyetherpolyol crosslinkers

Full bio-degradation of super absorbent hydrogels (SAHs), which possess excellent water uptake capacity, is still challenging. Based on Flory theory, this paper first analyzes that the high swelling property and gel strength of SHAs are attributed to the length of effective chain of crosslinker. Firstly, a series of hyperbranched crosslinker (HBC) with different molecular weights were designed and synthesized by anionic polymerization and sodium lignosulfonate (SL), which owns a hydrophilic network and remarkable biodegradation properties, was selected as a monomer. Compared with the shorter chain formaldehyde-urea crosslinker (SL-FU), the swelling performance of the gel is improved by about 22 % when long chain polyethylene glycol is used as crosslinker (SL-PEGDA400). Furthermore, SL crosslinked with HBC (PSLH) showed the highest water absorption properties of 664.3 g/g in deionized water and 69.8 g/g in normal saline water when the adding amount of HBE was 11.25 % (ratio to mass of SL, Mn = 5600 g/mol), which is about 16 times and 14 times higher than that of SL-Fu and SL-PEGDA400, respectively. The rate of natural degradation was over 96 %, which was buried in the soil for 270 days. In addition, PSLH as a substitute for petroleum-based products was applied in diapers, showing high adaptability, which indicated promising applicability for producing commercial hygiene productions.