Abstract
The mechanical performance in the wet state needs to be significantly improved and the intrinsic functionalities should be fully utilized to promote the replacement of fossil-based plastics with renewable biobased materials. We demonstrate a leather-inspired approach to produce multifunctional materials with a high wet strength that is based on tannin-induced precipitation of gelatin grafted onto surface-modified cellulose nanofibrils (CNF). The leather-inspired CNF-based films had a wet tensile strength of 33 MPa, a Young's modulus of 310 MPa, and a strain at failure of 22%, making the wet materials stronger than, for example, dry conventional low-density polyethylene and more ductile than paper-based food packaging materials. The tannin-containing films displayed excellent antioxidant and UV-blocking properties, rapidly scavenging more than 90% of added free radicals and absorbing 100% of light in the UV-B/UV-C range. This work illustrates the prospect of combining renewable materials in a leather-inspired approach to form wet strong and multifunctional films with potential application in food packaging.