Influence of Molecular Weight on Functional Performance and Migration of PLA Food‐Contact Films

ABSTRACT Although research on polylactic acid (PLA) films for food packaging applications has been expanded, the role of molecular weight in governing functional performance and chemical migration has not been comprehensively established. This study examines the influence of molecular weight on the thermal, mechanical, and barrier properties, as well as migration behavior of PLA films prepared from two commercial grades (PLA 2003D and PLA 4043D) by blown film extrusion. Gel permeation chromatography confirmed that PLA 2003D possesses a higher weight‐average molecular weight and broader molecular weight distribution than PLA 4043D. As a consequence, PLA 2003D exhibited higher thermal transition and degradation temperatures, improved tensile and impact properties, and lower oxygen and water‐vapor permeability, consistent with restricted chain mobility and increased chain entanglement. Migration experiments conducted with different food simulants showed that overall migration was higher for the lower‐molecular‐weight PLA 4043D, whereas slightly higher lactic acid‐specific migration was observed for PLA 2003D in 95% ethanol. For both PLA films, migration increased with simulant aggressiveness in the order 95% ethanol > 10% ethanol > 3% acetic acid. These results clarify structure–property–migration relationships in PLA films and support molecular‐weight‐guided design of food‐contact‐compliant, sustainable packaging materials.