Fabrication of polylactic acid films using lignocellulose-based green solvents as a sustainable alternative to hazardous solvents

This study investigated the solvent processing of polylactic acid (PLA) films using three green solvents derived from lignocellulose resources, i.e., dihydrolevoglucosenone (Cyrene), dimethyl isosorbide (DMI), and gamma-valerolactone (GVL). These bio-based solvents offered a sustainable alternative to conventional hazardous solvents commonly used in PLA film casting, such as chloroform (trichloromethane, TCM) and dimethylformamide (DMF). The results indicated that PLA can be steadily dissolved in these green solvents at elevated temperatures (e.g., 85 °C), with solution viscosity strongly influenced by both PLA concentration and processing temperature. Neat PLA films and PLA biocomposite films containing cellulose nanofibers (CNF), Kraft lignin, and lignosulfonate (LS) were successfully produced by optimizing evaporation and nonsolvent induced phase separation (E-NIPS) as the coagulation technique. Characterization of morphology, thermal stability, mechanical properties, and surface wettability demonstrated that PLA films prepared using green solvents exhibited comparable physical compactness and properties to those processed with TCM and DMF. Additionally, the incorporation of lignocellulose fillers influenced the thermal and mechanical properties (e.g., reinforcement effects from CNF) as well as optical properties (e.g., UV-blocking effects from lignin and LS) of the films. This study could contribute to advancing the sustainability of bioplastic processing for packaging applications by addressing the environmental concerns associated with toxic chemicals in solvent-casting PLA films.