Preparation and Evaluation of the Poly(lactic acid)-Cottonseed Oil Composite Films

Poly-(lactic acid) (PLA)-agricultural biomass composites represent promising renewable bioplastics for various industrial applications. This study investigated PLA-cottonseed oil (CSO) composite films prepared by solvent casting, incorporating 5-30 parts of refined and crude CSO per 100 parts of resin (phr), with neat PLA film as the control (PC0). No significant differences were observed between refined and crude CSO across all measured parameters, indicating that CSO from diverse sources and grades can be effectively utilized in film manufacturing. While all films remained colorless, the opacity decreased slightly with increasing oil content. Mechanical testing revealed that tensile strength decreased progressively from 169 MPa (PC0) to approximately 20-30 MPa in 30-phr films; however, flexibility improved substantially, with elongation at break increasing significantly (p ≤ 0.05) by 46% to 230%, compared to PC0. Water vapor permeability increased with CSO incorporation, although plasticizer migration was not a significant concern. Scanning electron microscopy coupled with energy-dispersion X-ray spectroscopy revealed smooth surfaces with a "CSO-rich islands and PLA-matrix sea" morphology, while Fourier transform infrared spectroscopy further confirmed molecular interactions between PLA and CSO, likely through structural cross-linking and surface shielding of CSO by PLA. These findings demonstrate that PLA-CSO formulations provide balanced mechanical performance and flexibility suitable for food packaging applications.