Abstract
Brittleness has hindered commercialization of cellulose nanofibril (CNF) films. The use of synthetic polymers and plasticizers is a known detour that impairs biodegradability and carbon footprint of the product. Herein, we utilize a variety of softwood Kraft lignin morphologies to obtain strong and ductile CNF nanocomposite films. An optimum 10 wt % content of colloidal lignin particles (CLPs) produced films with nearly double the toughness compared to a CNF film without lignin. CLPs rendered the films waterproof, provided antioxidant activity and UV-shielding with better visible light transmittance than obtained with irregular lignin aggregates. We conclude based on electron microscopy, dynamic water sorption analysis, and tp-DSC that homogeneously distributed CLPs act as ball bearing lubricating and stress transferring agents in the CNF matrix. Overall, our results open new avenues for the utilization of lignin nanoparticles in biopolymer composites equipped with versatile functionalities for applications in food packaging, water purification, and biomedicine.
Highlights
Renewable plant biomass is a viable alternative to fossil carbon resources in the production of materials and chemicals
The objective of this work was to gain fundamental understanding of how morphology of lignin, that is, whether it is added as well-defined colloidal spheres or as lignin powder, surface charge, and lignin content affect the properties of cellulose nanofibril (CNF)−lignin nanocomposites
Colloidal lignin particles termed colloidal lignin particles (CLPs) are spherical lignin particles prepared through solvent exchange process with a few modifications.[25]
Summary
Renewable plant biomass is a viable alternative to fossil carbon resources in the production of materials and chemicals. As contrasted to the production of platform chemicals from wood, it would appear more lucrative to isolate and use lignocellulosic biopolymers in their polymeric form with a lower energy penalty and moderate production cost. Biobased nanocomposites from renewable resources are generation materials with untapped potential for replacing conventional petroleum-based composites in various applications such as biodegradable packaging for food and beverages, biomedical materials for wound dressings and as membranes in water treatment technology.[1,2] Important properties in the aforementioned applications include ductility and strength, UVshielding, water resistance, tunable porosity, biocompatibility, and low cytotoxicity. The inherent structural heterogeneity and brittleness of lignin and hydrophilicity of cellulose have to date obstructed their composite use, despite the synergistic coexistence of lignin and cellulose in plant cell walls.[1,3−5]
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