Enhancing PVA mulching films: Leveraging modified lignin as a bio-based crosslinking agent for improved mechanical strength, UV barrier, and biodegradability

In contemporary agriculture, eco-friendly mulching films present a promising alternative to conventional plastic mulching films. However, their potential is constrained by challenges related to limited biodegradation and barrier performance. Addressing these limitations, innovative lignin-carboxylated materials were employed as bio-based crosslinking agents to enhance diverse properties in the fabrication of PVA films. Alkali lignin was modified with diethylenetriaminepentaacetic acid (DTPA) to enhance its chemical reactivity. The abundance of carbonyl groups in modified lignin (Lig-DTPA) plays a significant role in establishing strong compatibility with PVA through covalent bonds. This interaction yielded remarkable enhancements, elevating both tensile strength and tensile modulus by an impressive 50.9 % and 60.1 %, respectively. The introduction of Lig-DTPA at 3 % into the PVA composite films resulted in excellent UV-blocking properties. Moreover, at 3 % ratios, the presence of lignin became visibly dispersed as clear spots across the film, indicating a relatively uniform state within the matrix. The study revealed a direct correlation: as the lignin content increased, the film exhibited heightened water solubility and enhanced biodegradability. The PVA/Lig-DTPA film displays promising potential for utilization as a mulching film material, offering anti-ultraviolet functionality and a high degradation rate. Furthermore, its versatility extends to potential applications in packaging materials, including seedling bowls, transplanting pots, and coating films for transportation purposes.