Tunable mechanical performances of collagen-based film: Effect of collagens in different hierarchies and cellulose nanofiber

This study examines the effect of three collagens and the addition of carboxymethylated cellulose (CNF) on the properties of collagen-based film. The three collagens include macroscale collagenous fiber bundle (Ma-COL), microscale collagen fiber (Mi-COL), and nanoscale collagen fibril (Na-COL). With the decrease of the collagens' size, the viscosity of the dispersions decreased dramatically, besides, the collagen-based film showed an increased elastic modulus (from 13.32 GPa to 24.47 GPa) and tensile strength (from 46.18 MPa to 72.73 MPa). The opacity first decreased and then increased when the collagen's size ranged from macro- to nanoscale. The decrease of collagen's size could increase the film density and possessed more hydrogen bonds of film captured by FTIR. The addition of CNF further intensified the above trends. Besides, the reinforcing mechanisms of CNF could be proved by the combination of pull-off and intercrystalline fracture from microstructure and the finite element models.