Flexible and Gas-Resistant Films Based on Cellulose Nanofiber and Poly(butylene adipate-co-terephthalate)

Cellulose nanofiber (CNF) has attracted increasing attention as a sustainable nanomaterial for high-performance films due to its renewability and outstanding mechanical properties. However, the practical applications of CNF films are largely hindered by their insufficient tensile flexibility and gas barrier performance. In the present work, a reinforced, multifunctional nanocomposite film was prepared via the solution casting method by incorporating CNF with poly(butylene adipate-co-terephthalate) (PBAT). The influence of PBAT loading on the mechanical flexibility and barrier performance of the nanocomposite film was investigated, and the interfacial bonding characteristics were also studied. As a result, the composite film containing 40 wt% PBAT (denoted as CNF-PBAT40) exhibited a tensile strength of 49.6 MPa, which is generally seven times higher than that of the pristine CNF film. Moreover, its flexibility was notably enhanced, reaching an elongation at break of 7.8%. Additionally, the CNF-PBAT40 composite film showed a markedly reduced air permeability of 2.6 μm·Pa−1·s−1, compared with 9.5 μm·Pa−1·s−1 for the pristine CNF film. Therefore, these synergistically enhanced properties render CNF-PBAT composite films promising candidates for advanced applications in next-generation sustainable packaging.