Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE A novel bio-derived additive synthesized from tung oil and rosin synergistically enhances polylactic acid films. Integrating flexible aliphatic chains with a rigid cationic skeleton, the modifier resolves inherent brittleness, UV transparency, and poor antibacterial activity. The resulting non-migratory composites exhibit exceptional toughness, superior UV-shielding, and potent antimicrobial properties, effectively extending food shelf life.

ABSTRACT
The application of biodegradable polylactic acid (PLA) in food packaging is limited by its inherent brittleness, lack of UV resistance, and poor antibacterial activity. Here, we developed a multifunctional PLA-based composite film incorporating a novel bio-derived additive (EMB) synthesized from tung oil and rosin. The EMB molecule was designed with a structural synergy combining flexible aliphatic chains and a rigid cationic skeleton. Successful synthesis was confirmed by the disappearance of the 847 cm−1 epoxy band in FT-IR and the emergence of quaternary ammonium signals at 3.0–3.2 ppm in 1H NMR. The optimal film containing 6 wt% EMB exhibited overall performance, with an elongation at break of 163.3%, antibacterial efficiencies against E. coli and S. aureus of > 85%, and a UV-shielding efficiency of > 99% across the 200–315 nm wavelength range. Synergistic effects of internal plasticization, strong UV absorption, and electrostatic contact-killing contributed to the multifunctional enhancement. Furthermore, with a low migration rate below 1 mg/kg, the film effectively delayed the photo-oxidation of flaxseed oil and extended the shelf life of fresh strawberries.