Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Schematic illustration of the solvent-fractionation of alkaline lignin and its integration into PVA/KGM films through citric acid-mediated ester crosslinking.

ABSTRACT
The limited compatibility between lignin and hydrophilic polysaccharide–polymer matrices restricts the development of high-performance bio-based packaging films. Here, we propose a green strategy that incorporates solvent-fractionated alkaline lignin (F-AL) into konjac glucomannan (KGM)/polyvinyl alcohol (PVA) films through citric acid (CA)-mediated ester crosslinking. Fractionation using acetone/water enriched phenolic hydroxyl groups and reduced molecular weight, thereby enhancing lignin reactivity toward CA and improving its dispersion in the PVA/KGM matrix. FTIR and SEM analyses confirmed the formation of a denser crosslinked network and markedly improved interfacial compatibility. As a result, the optimized PKFAL6 film exhibited high tensile strength (40.27 MPa), a 54.8% reduction in water vapor permeability, and a low swelling ratio (112.47%). The enriched phenolic structure of F-AL imparted strong antioxidant activity (up to 85.6% DPPH scavenging) and excellent UV-blocking ability (91.4% UVB; 58.9% UVA). Soil-burial tests revealed a two-stage degradation behavior, with slower early-stage mass loss due to antimicrobial effects and accelerated degradation after network cleavage. These results demonstrate that lignin fractionation is an effective strategy for creating sustainable films with enhanced soil degradation performance and improved functional properties for active packaging.