Transparent Cellulose/Technical Lignin Composite Films for Advanced Packaging

Area of Science:

• Polymer Science
• Materials Chemistry
• Biomass Valorization

Background:

• Natural lignin products show promise for functional composites.
• Challenges exist in high-value applications due to lignin's complexity and inhomogeneity.
• Technical lignins from emerging pretreatment systems offer potential for material development.

Purpose of the Study:

• To assess four technical lignins from novel pretreatment systems for cellulose-based functional films.
• To comparatively identify phenolic substructures using 31P NMR.
• To evaluate the influence of lignin structure on antioxidant and UV-shielding performance.

Main Methods:

• Four technical lignins were obtained using deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone (Soda/AQ), and sodium salicylate hydrotrope pretreatments.
• Phenolic substructures were identified using 31P Nuclear Magnetic Resonance (NMR) spectroscopy.
• Cellulose/technical lignin composite films were prepared and their antioxidant and UV-shielding properties were assessed.

Main Results:

• Technical lignins from severe organosolv and Soda/AQ pretreatments exhibited higher total phenolic hydroxyl groups and antioxidant activities.
• Composite films demonstrated effective UV-blocking, particularly in the UVB region, at low lignin content (5 wt.%).
• Syringyl > guaiacyl > p-hydroxyphenyl phenolic hydroxyl groups contributed most to antioxidant activity and UV-shielding.

Conclusions:

• Technical lignins from specific pretreatment methods can enhance cellulose films with valuable functional properties.
• Lignin's phenolic substructure is critical for its antioxidant and UV-blocking efficacy.
• This research provides insights for optimizing lignin extraction and its value-added applications.