Dual Cross-Linked Gelatin-Based Adhesive for Leather with Low Curing Temperature and Improved Bonding Strength

Gelatin-based adhesives have limited practical application due to their bonding strength and high curing temperature. In this paper, we prepared a dual cross-linked water-based adhesive from waste leather-extracted gelatin, dialdehyde-TOCNF, and polymethacrylate adhesive. The dialdehyde-TOCNF cross-linking with gelatin is accomplished through the Schiff base reaction, and poly(methacrylic acid) was introduced to form hydrogen bonds with gelatin. The optimal bonding strength of the developed adhesive is achieved within a curing time of 40 min at a temperature of 50 °C, which is lower than the shrinkage temperature of leather. The adhesive exhibited exceptional mechanical performance, with the T-peel strength and wet peel strength reaching 1081 and 400 N/m, respectively. The adhesive shows good bonding ability on hydrophilic substrates such as wood, and the dry and wet bonding strengths with wood were 5.52 MPa (57.72% higher than gel) and 4.71 MPa (1780% higher than gel), respectively. It highlights the versatility of adhesives in different materials.