Improved stabilisation of graphite nanoflake dispersions using hydrothermally-produced nanocellulose

Dispersing graphite nanpoflakes in aqueous suspension is essential both during their processing and to realise the high level of functionality they offer. In this study two types of chemical-free nanocelluloses were assessed as possible dispersing agent for graphite nanoflakes. Hydrothermally-produced nanocellulose (HTC) obtained by supercritical water treatment of microcrystalline cellulose, showed superior dispersing than the more conventional, mechanically-produced microfibrillated nanocellulose (MFC) alternative, effectively preventing nanoflake agglomeration. Thanks to the specific processing method, the HTC material displayed higher total surface energy and a favourable particle morphology. These properties resulted in a 2-fold reduction in the volume median colloidal particle size of nanographite in suspension upon addition of only 2 w/w% nanocellulose. The improved single particle dispersion within the suspension matrix could be observed microscopically and was reflected rheologically. The latter was achieved by parameterising the stress-shear rate response and fitting the linear segments displaying the suspension coupling response. Using chemical-free nanocellulose as dispersant in aqueous medium is a positive step toward the exfoliation of nanographite into graphene in a more affordable and environmentally-friendly way.