Cellulose-based hydrogels with interpenetrating networks for 3D-printed cushioning materials

The rise of additive manufacturing technology has enabled the personalization of cushioning materials. This study developed a cellulose-based hydrogel that can be 3D printed, featuring a crosslinked interpenetrating network (IPN) of hydroxypropyl cellulose (HPC)/methacrylic anhydride-modified polyvinyl alcohol (PVA-MA) reinforced with carboxylated cellulose nanofibers (CNF) and quaternized chitosan (HACC). Multiple characterization techniques confirmed the successful construction of the crosslinked interpenetrating network structure, and the relationship between the hydrogel's crosslinked network structure and its cushioning performance was investigated. We rigorously confirmed that sodium citrate solution post-treatment induces ionic crosslinking significantly boosts the cushioning performance of the hydrogels, via comparative analysis of PMHI and PMHI-Na samples. Specifically, at 50% compressive strain, it demonstrated an energy loss coefficient of 61.4%, a Young's modulus of 448.22 kPa, and a static minimum cushioning coefficient below 0.5. Its performance surpassed that of traditional commercial cushioning materials like expanded polyethylene (EPE) and expanded polystyrene (EPS). To address customized demands for cushioning packaging, the printability of hydrogels for additive manufacturing (3D printing) was systematically investigated. Hydrogels containing ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L), a high-efficiency UV photoinitiator, demonstrated rapid curing rates while exhibiting compressive strengths up to 547.40 kPa and elongation at break up to 229.40%, enabling high-quality 3D printing. This work provides a promising approach to biomass-based cushioning materials with improved mechanical properties and 3D printability, advancing the large-scale application of biomass cushioning materials.