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Green preparation of nanocellulose/H2O2-modified lignin composite films and their antibacterial, flame-retardant, and food preservation properties
Summary
Scientists created a new food packaging film made from plant fibers and treated wood waste (lignin) instead of petroleum-based plastic. In tests, it kept cherry tomatoes fresh for 15 days, blocked UV rays, resisted fire, killed over 99.99% of bacteria, and broke down almost completely in soil within two months. This matters because it points toward packaging that could reduce our reliance on plastics linked to microplastic pollution, while also keeping food safer and fresher for longer.
Developing sustainable packaging materials is vital to mitigating petroleum-based plastic pollution. While natural biomass materials like cellulose and lignin offer immense potential, the broad application of alkaline lignin is hindered by its deep chromaticity and poor interfacial compatibility. Herein, we propose a green, scalable hydrogen peroxide (H2O2) oxidation strategy to prepare modified lignin (L-Hx) as a multifunctional reinforcing phase for cellulose nanofiber (CF) composite films. This modification achieves efficient decolorization and significantly increases the hydroxyl content of lignin from 2.78 to 5.89 mmol/g, facilitating robust hydrogen bonding interactions with the CF matrix. At 16.7 wt% L-Hx loading, the composite film delivers a remarkable tensile strength of 73.6 MPa. Molecular dynamics (MD) simulations further elucidate this strengthening mechanism, revealing a surge in intermolecular hydrogen bonds from 281.1 to 781.3. Notably, the unique structural properties of modified lignin endow the film with near-complete UV shielding, exceptional flame retardancy (LOI of 40.1%), and superior antibacterial activity (> 99.99%). Moreover, the film extends the preservation of cherry tomatoes to 15 days and exhibits near-complete macroscopic degradation in soil within 60 days. By elucidating the “structural regulation-interfacial interaction-property enhancement” relationship, this study paves a robust pathway for high-value lignin utilization and the rational design of high-performance, multifunctional bio-based packaging.