A partial dissolution-regeneration strategy for preparing water-resistant composite film of cellulose I and cellulose II with high light transmittance and adjustable haze

Due to the excellent properties of nanocellulose film such as biodegradability and renewability, researchers have conducted in-depth research on it in recent years. However, rich hydroxyl groups on the surface of nanocellulose make it hydrophilic, and small gaps between the fibrils have significant capillary effect, which cause the strength of nanocellulose film drastically deteriorates when exposed to water, severely restricting its scope of use. In this study, the nanocellulose prepared by ball milling was used to prepare nanocellulose film, and the surface of the film was partially dissolved by ZnCl2. The dense regenerated cellulose (Cellulose Ⅱ) with Zn2+ on the surface made the film hydrophobic, effectively reduced the water absorption rate of the film, and also maintained the internal structure of the nanocellulose. Through this strategy, the nanocellulose film with high dry strength (151–176 MPa), wet strength (27.6–31.7 MPa), high light transmittance (80–91%), and adjustable haze (50–90%) was obtained. This study provides a facile and environmentally friendly strategy to improve the wet strength of nanocellulose film, which broadens its application prospect in packaging materials and electronic devices.