Influence of Polymer Swelling and Dissolution in Food Simulants on the Release of Graphene Nanoplates and Carbon Nanotubes from Poly(lactic) acid and Polypropylene Composite Films

The study compared the effects of swelling and dissolution of a matrix polymer by food simulants on the release of graphene nanoplates (GNPs) and multiwall carbon nanotubes (MWCNTs) from poly(lactic) acid (PLA) and polypropylene (PP) composite films. The total migration was determined gravimetrically in the ethanol and acetic acid food simulants at different time and temperature conditions, while migrants were detected by laser diffraction analysis and transmission electron microscopy. Swelling, thermal analysis, and scanning electron microscopy were applied to characterize the degradation of polymer films at the migration conditions. The release of nanoparticles was found in a high-temperature migration test of 4 h at 90 °C. The hydrolytic dissolution of the PLA polymer in the food simulants caused a migration of GNPs (>100 nm) from the PLA/GNP/MWCNT films into the simulant solvents, while the entangled MWCNTs formed a network on the film surface, preventing their migration from the PLA composite films. In contrast, the PP polymer slightly swells in ethanol solvents, allowing some short carbon nanotubes to be released from the surface and cut edges of the PP/MWCNT film into food simulants. Mathematical modeling of diffusion was applied that accounts for type of polymer, time–temperature conditions, and solvent concentration; model parameters were validated with experimental results. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45469.