Curaua and eucalyptus nanofiber films by continuous casting: mixture of cellulose nanocrystals and nanofibrils

Over the last few years, there has been a great interest in the production of cellulose nanofiber films. However, conventional casting and film with only one kind of nanofiber may give rise to brittle material. Furthermore, films formed by the mixture of cellulose nanocrystal (CNC) and cellulose nanofibril (CNF) by continuous casting have not been reported. In this way, this study aims to investigate the optical, thermal, mechanical, and physical properties of the mixture of CNC and CNF films obtained by continuous casting from curaua and eucalyptus fibers at the proportions of 0/100, 25/75, 50/50, 75/25, and 100/0 (% w/w). After continuous casting, neat CNC and neat CNF are cleared oriented, causing anisotropic mechanical properties. On the other hand, the mixture of CNC and CNF made the films mechanically more isotropic, even though some degree of orientation of the fibers. The films with a mixture of CNC/CNF 25/75 (% w/w) were more thermally stable. The addition of CNC in CNF films decreased their opacity. Thus, the type of nanofibers, the cellulose source, the process, and the mixture of CNC/CNF affect the properties of the films significantly.