Regenerated Cellulose Films Coated with Waterborne Polyurethane with Enhanced Mechanical Properties

Regenerated cellulose (RC) films with abundant sources and low processing costs are considered to be excellent biodegradable and recycled packaging materials. However, there is still a problem to be solved: the poor strength of RC films in the wet state. Polyurethane (PU) possesses excellent mechanical properties, biocompatibility and biodegradability. In this work, a PU coating is successfully introduced on the RC film surface via a facile surface engineering strategy, followed by plane hot-pressing process, and the RC@PU films are obtained. Notably, under wet conditions, RC@PU films show outstanding mechanical properties (fracture stress of 22.5 MPa, fracture strain of 75.9%, toughness of 10.6 MJ/m³), which are greater than those of the pure RC films (18.9 MPa, 56.5%, 6.9 MJ/m³). In addition, RC@PU films play an important role in anti-water evaporation tests. Moreover, RC@PU films exhibit excellent biodegradability, which can be completely degraded in a natural environment in about 70 days. This work provides a simple and feasible surface engineering strategy for developing RC films with excellent wet strength and biodegradability.