Structural change and redispersion characteristic of dried lignin-containing cellulose nanofibril and its reinforcement in PVA nanocomposite film

Having the advantages of a higher yield, lower cost and less environmental impact, lignin-containing cellulose nanofibrils (LCNFs) obtained by mechanically fibrillating unbleached pulps have been demonstrated to be a promising alternative to high-purity nanocellulose. In this study, the structural changes after four drying methods containing freeze-drying (FD), oven-drying (OD), centrifugal followed by vacuum-drying (CVD), and evaporation followed by vacuum-drying (EVD), and efficient reuse of LCNFs were extensively explored. It was found that the structural characteristics of LCNFs after drying were maintained by freeze drying with high lignin contents where the aggregation of fibrils was alleviated by lignin. The freeze-dried LCNFs were further redispersed by homogenizer in water, which exhibited excellent dispersion characteristics. In addition, the redispersed LCNFs were further assembled into PVA films to fabricate high-strength composites. The results showed that when the addition of redispersed LCNFs was up to 16.9%, the tensile strength and elongation at break of the as-prepared composite film increased by 325.2% and 335.2%, respectively. This study demonstrated a more sustainable approach to utilize LCNFs to produce biomass-based composite films than those of CNF-based composite films.