Preparation of Poly(ethylene adipate- co -terephthalate) (PEAT)/Thermoplastic Starch (TPS)/Lignin Ternary Composite Film with Excellent UV-Shielding and Barrier Properties via Sustainable High-Value Utilization Strategies for Lignin

This study employed triethoxyvinylsilane-modified lignin (VTES-AL) to prepare poly(ethylene adipate- co -terephthalate) (PEAT)/thermoplastic starch (TPS)/lignin composite films. The resulting composites demonstrated enhanced mechanical properties, UV barrier performance, and water-oxygen barrier properties. The effects of silane modification and VTES-AL content on the properties of PEAT/TPS composite films were systematically evaluated. A series of PEAT/TPS/VTES-AL composite films were subsequently characterized for their chemical structure, mechanical properties, thermal behavior, water absorption, and light/water/oxygen barrier properties. The results indicate that silane-modified lignin exhibits excellent dispersion within the polymer matrix. Interactions between VTES-AL and the polymer chains significantly enhance the mechanical properties of the composite films. The addition of 1 wt % VTES-AL increased the tensile strength and tensile modulus by 28% and 21%, respectively. Furthermore, VTES-AL incorporation enhanced the crystallinity of the composite film, with the addition of 5 wt % VTES-AL leading to a 65% increase. The light transmittance of the film decreased significantly, demonstrating excellent UV absorption capabilities (99.7% shielding at 200–400 nm) and effectively preventing the photodegradation of PEAT. VTES-AL impedes the movement of permeating molecules within the composite, thereby enhancing the oxygen and water vapor barrier properties. This research offers a sustainable and innovative strategy for the high-value utilization of lignin and explores green pathways for the application of high-performance composite films.