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.