Assessment of Mass Transfer from Poly(ethylene) Nanocomposites Containing Noble-Metal Nanoparticles: A Systematic Study of Embedded Particle Stability

Polymer nanocomposites (PNCs), which consist of a polymer host and a nanomaterial filler, may become useful as food packaging materials due to their enhanced properties compared to neat polymers. Many studies have explored release of embedded nanomaterials or their components from PNCs into foods and food simulants. However, more studies are needed that systematically study the mechanistic role that nanoparticle (NP) and polymer characteristics play in determining mass transport from these materials. Here, noble-metal-containing nanoparticle (NP)/low density poly(ethylene) (LDPE) PNCs were used as model food contact materials to decouple the impact of nanofiller size, composition, and stability on release into two food simulants (water and 3% acetic acid). PNCs containing Ag NPs ranging in diameter from 4 to 41 nm were first evaluated. We found that ～1% of Ag mass was released from PNCs incorporating Ag NPs > 10 nm, but the percent of released Ag increased dramatically when the Ag NP diameter was <10 nm (52% release was measured when the NP diameter was 4 nm). By comparison, mass transfer from PNCs incorporating similarly sized, more stable Ag2S NPs and Au NPs was very low (<0.1%). We also found that the simulant chemistry and experiment time impact total mass transfer from these PNC films. These experiments are the first to show a direct link between NP size/composition and potential mass transfer to food simulants, and they support a model in which NP stability against oxidative dissolution plays a dominant role in determining consumer exposure in a food contact application. The results will help inform design strategies for PNCs that have reduced likelihood of mass transfer to aqueous environments