Safety aspects of polymer films with atomic layer deposited Al2O3 thin layers

Atomic layer deposition (ALD) is an efficient tool for improving the barrier properties of polymer films and polymer-coated papers/paperboards. However, adequate barrier properties are only one of the key requirements set for the packaging materials. Purpose of this paper is to present the safety aspects related to polymer films with a thin ALD grown Al2O3 layer. Several approaches were tested. Based on our analyses ALD grown Al2O3 thin layers do not fall under the European Commission's definition of nanomaterial, and thus the limitations set in the Commission Regulation (EU) No 10/2011 on plastic materials would not be valid in this case. Al2O3 is also accepted as an additive for plastics in contact with food. Abrasive testing of polymer films, although detrimental in several cases to the film itself, did not increase the number of airborne particles. Coated silicon wafer and oriented polymer films were also exposed to specific simulants and key material properties were followed. Finally, we also tested the films for migration, although overall migration from a similar thin film has been regarded extremely low. Our tests were based on the worst case scenario, where the thin inorganic layer is exposed directly to the simulant. The Al2O3 coated films were affected by the simulant exposure, but the degree of impact depended also on the base film. This could indicate different thin layer growth on different polymer films. As a conclusion, such ALD grown Al2O3 thin layers require additional protective layers acting also as a sealant layer.