Multilayer Cellulose Acetate–Viscose Films for Bio‐Based, Bio‐Degradable Packaging Applications

In an attempt to produce bio‐based and biodegradable packaging films, cellulose acetate (CA) and viscose films were combined to form a multilayer film structure. The viscose film was immersed in dilute sodium hydroxide solutions (0.1–0.5 mol/L) and then subjected to heated compression to improve adhesion to CA. Film adhesion was determined using a T‐peel test, and the results suggest that the optimal conditions are 118 bar and 110°C for 10 min. Immersing the composite in a 0.25 mol/L dilute sodium hydroxide (NaOH) solution enables firm adhesion between the two films and results in balanced saponification of the CA without substantial degradation of the matrix. The water vapour barrier properties of the multilayer films increase as the CA thickness increases. Interestingly, facing the CA towards the water vapour‐rich side results in decreased permeation compared to the inverse case. However, the oxygen barrier property of the multilayer film is significantly reduced due to the NaOH pre‐treatment, and the oxygen barrier property of the viscose film is lost.