A Room‐Temperature Curing Plant Protein‐Based Adhesive with High Strength and Flame Retardancy for Heat‐Free Adhesion

Abstract

Plant protein‐based adhesives are gaining traction owing to their low cost and eco‐friendliness. However, achieving flame retardancy and long‐term water resistance in them under room‐temperature curing conditions remains a challenge due to the hydrophilicity and low reactivity of plant proteins. Herein, a novel adhesive synthesized from soybean meal (SM), activated sodium alginate (aSA), nano‐hydroxyapatite (nHA), and polyamidoamine‐epichlorohydrin (PAE) resin addresses this challenge. aSA as a reactive bio‐based cross‐linker formed covalent cross‐linking structures with SM matrix at room temperature, while the nHA‐induced biomineralization and PAE‐constructed supramolecular cross‐linking promote water drainage from the adhesive, preventing water erosion of the adhesive structure. The developed adhesive shows versatility across multiple substrates, with its wet shear strength on wood reaching 0.76 MPa, surpassing that of the commercial aldehyde‐based adhesive. The adhesive is effective over a wide temperature range from room temperature to 150 °C due to the reactivity of the PAE resin above 60 °C. Moreover, it exhibits excellent flame retardancy (limiting oxygen index of 31.2%) owing to its dense structure and the abundance of N‐containing and P‐containing components. This work is expected to break the monopoly of petroleum‐based adhesives in the realm of room‐temperature adhesives.

Enzyme-Induced “Sea–Island” Structure Reinforced Bio-Based Adhesive: Toward High Bonding Strength, Toughness, and Bacterial Resistance

“…Figure h showcases the surface crack conditions of the SM-based adhesives, which assessed their toughness. While large cracks developed on the SM adhesive, the SM/Ker/0.4%La@SA and SM/Ker/0.8%La@TSA adhesives exhibited dense and smooth surfaces without cracks or holes, indicating improved toughness . The force–distance curves and work of adhesion revealed that the work of adhesion of the SM/Ker/0.4%La@SA adhesive increased to 0.60 J, a 71.4% increase compared with the SM adhesive (0.35 J) (Figure i).…”