High performing barrier films of nanocellulose and graphene

Nanocellulose films and coatings are growing in interest to be used as gas barriers in various packages and devices due to their high oxygen barrier. However, barrier against water vapor is moderate and the oxygen barrier also rapidly reduces as the relative humidity (RH) of the surrounding environment increases. Thus, for nanocellulose films/coatings to be industrial applicable the oxygen permeability (OP) at high RH and the water vapor permeability (WVP) needs to be significantly reduced. Another aspect is the energy demanding production for films and coatings due to the high amount of water to be removed. Forming nanocomposites by adding a flaky impermeable material to the nanocellulose matrix is a common strategy for improving barrier performance. Graphene is such a material. Its aspect ratio is very high which, theoretically, could provide a very long tortuous path, in turn enhancing the barrier performance. We show here that by carefully selecting graphene and CNF qualities and using proper mixing methodologies films with excellent gas barrier properties can be formed. We also investigate how well the graphene is utilized by characterizing its orientation within the films, as well as how the graphene addition influences the films mechanical properties. Finally, we demonstrate a new in-house developed scalable and energy efficient roll-to-roll production process: gel extrusion.