A novel technique in the preparation of environmentally friendly cellulose nanofiber/silk fibroin fiber composite films with improved thermal and mechanical properties

In this paper, we report a novel technique which enabled us to easily and directly obtain a silk fibroin (SF) solution without the use of organic solvents by applying a simple grinder for silk cocoons. In addition, we successfully prepared cellulose nanofiber/silk fibroin (CNF/SF) nanofiber composite films using a filtration and pressing method from a slurry solution blended with a CNF solution. The peak temperature of the thermal decomposition of the SF nanofibers prepared using the new method developed in this research was improved by more than 13 degrees C, and that of the composite films compounded with more than CNF 50 wt% showed almost the same temperature as the CNF film. In addition, the mechanical properties of the CNF/SF nanofiber composite films were increased with increasing the amount of CNF. These results strongly suggest that the SF solution prepared using our novel method has advantages of superior thermal and mechanical properties compared with that prepared by a conventional method using a concentrated neutral salt solution. Additionally, this result indicates the film manufacturing method having advantages of water pollution reduction and energy saving. (C) 2019 Elsevier Ltd. All rights reserved.