Investigating the influence of polylactic acid (PLA) toughening on the release of graphene nanoplates into food simulants from PLA nanocomposite

This study explores the migration of graphene from poly(lactic acid) (PLA) matrices and examines how PLA toughening and compatibilization impact graphene release. Since PLA is inherently brittle and has limited flexibility, polyolefin elastomer (POE) is used to improve its mechanical properties and enhance its suitability for packaging applications. PLA and PLA/polyolefin elastomer (POE) nanocomposites with varying contents of graphene, POE, and POE grafted with maleic anhydride (POE-g-MAH) were prepared through melt extrusion, followed by molding and exposure to various food simulants under different conditions. The swelling, dissolution, degradation, total migration, graphene migration, and changes in thermal properties of the samples in contact with food simulants were analyzed. Additionally, the size distribution and structure of the released graphene were evaluated. It was found that higher graphene content and the addition of POE and POE-g-MAH significantly reduced polymer swelling, dissolution, and graphene release. PLA/graphene nanocomposites exhibited the highest swelling, degradation, and graphene migration, whereas enhanced stability was demonstrated by PLA/graphene/POE nanocomposites. This stability is attributed to the toughening agents and compatibilizers effectively impeding food simulant penetration and polymer degradation. Furthermore, the PLA matrix was crystallized by food simulants, particularly 50 % ethanol, resulting in a higher degree of crystallinity and an increased melting point after the migration test. Insights into improving the stability of toughened PLA/graphene based nanocomposites for food contact applications were provided by these results.