Hemp waste: production of nanocellulose and its use in fully biobased photocured composites

Hemp is a sustainable crop, grown either for textile fibers or for seeds. In the latter case, the stem is left behind as waste, and its recovery is desirable. First, we produced nanocellulose from hemp fibers obtained from waste stems: these underwent chemical, mechanical and enzymatic pre-treatment steps, before being processed in an ultrafine friction grinder to obtain nanocellulose. The dimensions and chemical composition of the fibers during all steps were monitored by optical and field emission scanning electron microscopy (FESEM), infrared spectroscopy (FTIR), and thermogravimetric analysis. The chemical pretreatment removed lignin and hemicellulose, opening up the fiber wall. The dimensions of the fibers were reduced throughout all treatment steps. The thermal and mechanical properties, and the permeability to water vapour of nanopaper prepared from nanocellulose (Fig. 2) were also assessed. Secondly, combining the nanocellulose with a photocured polymer matrix, derived from agri-food industry waste, we prepared composites, potentially usable in packaging. We selected a photopolymer matrix, being photopolymerization a green technology, owing to low energy requirements, high reaction rates, and low VOC emissions4. The extent of curing was evaluated by FTIR, and the thermal and mechanical properties were assessed. The preparation of sustainable composites derived from biomass (both filler and matrix), through the use of an environmentally friendly curing process, is therefore hereby demonstrated.