Enhancing the Ductility of Poly(lactic acid) With Acetylated Monoglycerides for Food Packaging Films: Impact of Hydrophobic Chain Length and Molecular Structure

Poly(lactic acid) (PLA), a biodegradable plastic, has the potential to replace conventional petroleum-based plastics due to its excellent mechanical performance, biodegradability, renewability, and biocompatibility. However, its inherent brittleness has limited its application in food packaging films. To overcome this limitation, acetylated monoglyceride (AMG), a food additive containing both a non-polar hydrocarbon chain and the polar carbonyl group of an ester, was evaluated as a plasticizer to enhance ductility. Among AMGs with various aliphatic chain lengths (C2:0 to C18:1), the cis-configured C18:1 AMG (diacetylated monoolein) exhibited superior mechanical performance compared to other AMGs, indicating a significant enhancement in the flexibility of plasticized PLA films. FT-IR and SEM analyses confirmed the homogeneous distribution and non-covalent interactions between C18:1AMG and PLA, maintaining the polymer's structural integrity. Thermal analyses revealed decreased glass transition and melting temperatures, suggesting increased chain mobility without compromising thermal stability. In addition, UV and visible light transmittance of PLA-C18:1AMG films effectively reduced enzymatic browning in fresh-cut potatoes, highlighting their potential for food packaging applications. Although the mechanical properties of PLA films plasticized with C18:1AMG do not fully reach those of conventional petroleum-based plastics, chemical modification of C18:1AMG or its formulation in blends with other plasticizers is expected to significantly enhance the mechanical properties of PLA.