Rapid nanopaper production by spray deposition of concentrated microfibrillated cellulose slurries

•Wet MFC mat formation by spray deposition of high concentration slurries.•Rapid dewatering and nearly total MFC retention.•Production of nanopaper with high modulus and resistance to air permeation.•Upscalable process for nanopaper production.

This study presents a rapid method for nanopaper production by spray deposition of high concentration microfibrillated cellulose (MFC) slurries on a nylon fabric and their subsequent filtration dewatering. The filtration time for the consolidation of a wet MFC mat was of 15 and 90 s for sheets with basis weight of 13.7 and 124 g m−2, respectively. MFC films exhibited excellent Young's modulus of ca. 18 GPa and intrinsic air permeability of ca. 0.22 nm2. Nevertheless, the progressive decrease of the basis weight from 124 to 13.7 g m−2 induced the decay of the film tensile properties (stress and strain at break dropped from 150 MPa and 4.6% to 50 MPa and 0.4%) and the onset of a brittle behaviour. This trend was ascribed to the presence of residual fibre debris in the MFC slurry which acted as fracture nucleation spots in thin films.