ORIGINAL RESEARCH High-performance homogenized and spray coated nanofibrillated cellulose-montmorillonite barriers Kirubanandan Shanmugam . Shaun Ang . Maisha Maliha . Vikram Raghuwanshi . Swambabu Varanasi . Gil Garnier . Warren Batchelor Received: 2 June 2020 / Accepted: 4 October 2020 Ó Springer Nature B.V. 2020 Abstract Nanofibrillated cellulose (NFC) is a promising candidate for the development of high- performance renewable packaging. The water vapour permeability (WVP) of NFC sheets can be improved with the addition of inorganic nanoparticles such as montmorillonite nanoclay (MMT). However, these nanoparticles reduce the already poor sheet drainage when layers are formed through vacuum filtration. Spray-coating, on the other hand, is a recently developed rapid method for sheet formation. How- ever, higher WVP of spray-coated NFC sheets com- pared to its vacuum filtered counterpart still remains a limitation. This work reports a new method for spray- coating a NFC-MMT composite sheet to improve both the ease of preparation and WVP barrier performance. Critically, the WVP of CNF sheets could be signifi- cantly reduced by processing the CNF-MMT suspen- sion in a high-pressure homogenizer prior to spray- coating. X-ray diffraction measurements confirmed that the MMT particles were aligned in the plane of the sheet and were strongly interacting with the NFC matrix. At the optimal MMT loading of 20 wt%, WVP of 8.3 9 10 -12 g/m s Pa was achieved. This resulted in comparable barrier performance to vacuum filtered NFC-MMT sheets, with the added benefit of being much easier to produce. Furthermore, spray-coating with 2 wt% suspension reduces the required water removal during drying by almost 90% (291 tonne water/tonne dry NFC product), compared to forming equivalent sheets using vacuum filtration at 0.3 wt%. The spray-coating process is of industrial interest as it is scalable and it is easy to engineer the properties of the NFC composites by varying the MMT content. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-020-03515-w) contains supplementary material, which is available to autho- rized users. K. Shanmugam  S. Ang  M. Maliha  V. Raghuwanshi  S. Varanasi  G. Garnier  W. Batchelor (&) Department of Chemical Engineering, Bioresource Processing Research Institute of Australia, Monash University, Melbourne, VIC 3800, Australia e-mail: warren.batchelor@monash.edu 123 Cellulose https://doi.org/10.1007/s10570-020-03515-w