Novel bridge assistance strategy for tailoring crosslinking networks within soybean-meal-based biocomposites to balance mechanical and biodegradation properties

Abstract

The cost-effective fabrication of environmentally friendly soybean meal (SM)-based biocomposites with tailorable biodegradability, mechanical properties, and water resistance remains a challenge. Herein, a novel bridge assistance strategy to effectively balance the performance of SM-based biocomposites was designed by constructing multiple tailorable networks using diethylenetriamine (DETA), melamine-urea-glyoxal (MUG), and polyamidoamine-epichlorohydrin (PAE) resins. The Schiff’s base reaction between DETA and MUG yielded a more reactive, branched DETA@MUG crosslinker, which could efficiently form co-crosslinks with long-chained PAE. Owing to the stronger bridge interactions of DETA, the obtained PAE/DETA@MUG co-crosslinks were more stable than those formed using PAE and MUG alone. Consequently, the PAE/DETA@MUG co-crosslinker system effectively reinforced the multiple networks and the performance of the SM-based biocomposites via the formation of more DETA@MUG–protein, PAE–protein, PAE–carbohydrate, and PAE–wood crosslinks, resulting in improvements in the dry tensile strength (158.2%) and water resistance (461.9%). Moreover, the multiple networks formed by branched DETA@MUG were beneficial for balancing the interior forces of the obtained SM-based resin, thereby improving its toughness by 64.3%. The DETA bridge also decreased the numbers of stable PAE–wood and PAE–SM bonds in the SM-based biocomposites while ensuring the necessary PAE/DETA@MUG co-crosslinks, which improved the biodegradation rate by 16.2% without compromising the mechanical properties and water resistance. Therefore, this bridge assistance strategy is highly suited for the commercial production of SM-based polymers and biocomposites with balanced mechanical properties, water resistance, and biodegradability.