Synergistic Effect of Sodium Alginate and Lignin on the Properties of Biodegradable Poly(vinyl alcohol) Mulch Films

Replacing petrochemical polymers with biomaterials for biodegradable mulch applications has attracted widespread attention. However, improving film performance and reducing costs remain an issue. In this work, we found that the synergistic effect of sodium alginate and quaternary lignin significantly improved the performance and reduced the cost of poly(vinyl alcohol) films. The water retention, ultraviolet (UV) resistance, heat collection, light transmission, mechanical properties, soil consolidation, and the degradation rates of the composite films were systematically studied. We found that the addition of lignin enabled the film to achieve complete UV resistance, while the sodium alginate synergistically improved the mechanical and water-holding properties of the film. The film improved soil slumping, and the water vapor permeability of the film was 109.2 g·m–2·day–1. The degradation of the film was facilitated by the self-degradation properties of sodium alginate and lignin, which degraded 55% after 50 days.