The results of our model system show that only the smallest spheric nano particles up to approximately 3.5 nm in diameter would have a potential to migrate in measurable concentrations if present at high amounts in a polymer. NPs in the diameter range 3–5 nm in diameter, again only if present in the polymer at high amounts, would have a potential to migrate but would cause migration rates that would not be measurable even with highly sensitive methods. It should be noted that in practice, nano materials usually do not show up in polymer composites as primary single particles in the diameter range below 5 nm. We have not found in the published literature any evidence that smaller NPs would occur in plastics nano composites for food contact applications. They usually have greater dimensions starting at 10– 20 nm and form aggregated structures and agglomerates being much larger and up to the 1000 nm range and larger. In case of our study, TEM images confirmed that TiN exists only as aggregates with dimensions typical larger than 100 nm. However, the modeled migration parameters and values for a spherical 10 nm particle already indicates a diffusion coefficient in the range of 1E35 cm2s1 and a migration value in the 1E18 mg kg1 range which is absurdly low and fully meaningless. This means that even larger and more complex structured (aggregated) substances, like it is the case for TiN and many other nano materials, will be fully immobilized in the host polymer and not leach out at all.
The results of our model system show that only the smallest spheric nano particles up to approximately 3.5 nm in diameter would have a potential to migrate in measurable concentrations if present at high amounts in a polymer. NPs in the diameter range 3–5 nm in diameter, again only if present in the polymer at high amounts, would have a potential to migrate but would cause migration rates that would not be measurable even with highly sensitive methods. It should be noted that in practice, nano materials usually do not show up in polymer composites as primary single particles in the diameter range below 5 nm. We have not found in the published literature any evidence that smaller NPs would occur in plastics nano composites for food contact applications. They usually have greater dimensions starting at 10– 20 nm and form aggregated structures and agglomerates being much larger and up to the 1000 nm range and larger. In case of our study, TEM images confirmed that TiN exists only as aggregates with dimensions typical larger than 100 nm. However, the modeled migration parameters and values for a spherical 10 nm particle already indicates a diffusion coefficient in the range of 1E35 cm2s1 and a migration value in the 1E18 mg kg1 range which is absurdly low and fully meaningless. This means that even larger and more complex structured (aggregated) substances, like it is the case for TiN and many other nano materials, will be fully immobilized in the host polymer and not leach out at all.
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