Maximizing Toughness and Accelerating In-Outdoor Degradation of PLA Films with Modified Cellulose Nanocrystals to Enhance Agricultural Practices

Polylactic acid (PLA) is widely used in crop protection but faces challenges such as low toughness and unpredictable degradation rates. This study addresses these limitations by developing a green and durable mulch film incorporating citric acid-modified cellulose nanocrystals (CA-CNC) as an interfacial compatibilizer in PLA. Adding CA-CNC enhances the orientation of PLA molecular chains, thereby improving tensile ductility. Specifically, incorporating 5% CA-CNC significantly increased tensile strength by 28.2%, while toughness surged by 190.1%. Mulch films were subjected to indoor UV light and outdoor degradation in soil and cultivation environments (using soybean as a case study) to explore degradation mechanisms. Notably, the mulch film with 5% CA-CNC completely fragmented after 140 days of soil degradation, representing a higher degradation rate of 31.9%. Meanwhile, the degradation rates observed after 90 days of outdoor cultivation environment degradation (9.8%) and 30 days of indoor UV degradation (2.8%) exhibit distinctions compared to outdoor soil degradation. Further analyses of changes in the physicochemical properties of mulch film confirmed the degradation mechanisms. This study provides valuable insights for estimating short-term indoor and long-term outdoor degradation of mulch films, underlining their significance in sustainable agricultural practices.