Addition of Fibroin to Tannin-Furanic Bio-Based Ad hesive for Plywood Product

Nowadays, one of the main challenges for developing new materials is the transition towards sustainable resources. Among the main attractive precursors for natural polymers, polyphenolic tannin extracts play a major role due to their availability, their chemical homogeneity and good reactivity with aldehydes and furanics. Indeed, the addition of crosslinker leads to tannin-based bioplastics suitable for several applications, however their low moisture resistance and their rigidity still limit the industrial applications of these products. Within the tannin derivate class, the fully-renewable tannin-furanic polymers have shown high potential as foam and adhesive, but they are not yet competitive against fossil derivatives. In this work, the synthesis of tannin-based biopolymers combined with fibroin, a protein derived by the silk regeneration is presented. Quebracho tannin-furfuryl alcohol (60/40) copolymers, added of fibroin were tested to evaluate the mechanical properties of three-layer plywood considering that the presence of protein could affect the elasticity of the network. The composite panel glued with tannin-furanic-fibroin adhesives were produced and underwent physical-mechanical testing. Significant improvement of mod ulus of elasticity, modulus of rupture and shear strength were registered when fibroin was added. Fur ther, preliminary test in wet environment highlighted also a good moisture resistance of the cured formulation. FT-IR ATR and 13C NMR allowed to determine the interactions between the formulation components, while the TMA analysis have shown its curing kinetics. The presence of fibroin in the tannin-based resins seems to enhance elasticity, mechanical properties and water resistance, opening new perspectives for the use of tannin resins as adhesive for solid wood.