Polyethylene terephthalate (PET) is widely used in food packaging, but the processing aids that include materials such as plasticizers and antioxidants may migrate to food, thereby harming the food quality and human health. To develop packaging materials with lesser plasticizer migration and to understand the anti-migration mechanism, a SiO x layer was deposited by plasma-enhanced chemical vapor deposition (PECVD) on a PET substrate to prepare a composite film. The effects of SiO x layers with different thicknesses on blocking the migration of dioctyl phthalate (DEHP, a plasticizer) and Irganox 1010 (an antioxidant) from the PET substrate into the food simulant were investigated at three temperatures. The migration of additives from both pristine and SiO x -coated films increased with an increase in the contact time and temperature. However, compared with the pristine film, the specific migration rates of DEHP can be reduced by up to 88.57% in the 320-nm SiO x /PET composite film, while that of Irganox 1010 can reach 82.61%. For a fixed SiO x layer thickness, the DEHP migration is not greatly affected by temperature, while that of Irganox 1010 migration decreased at higher temperatures. In addition, a 320-nm SiO x layer effectively retarded the transmission of water vapor and oxygen through the composite film to 77.3% and 79.3% lesser than those of the pristine PET film, respectively. The SEM image showed that the surface of the composite film was denser and more uniform than a pristine PET film, which also confirmed that the SiO x layer can block the migration of additives.
As novel materials for food contact packaging, inorganic silicon oxide (SiOx) films are high barrier property materials that have been developed rapidly and have attracted the attention of many manufacturers. For the safe use of SiOx films for food packaging it is vital to study the interaction between SiOx layers and food contaminants, as well as the function of a SiOx barrier layer in antioxidant migration resistance. In this study, we deposited a SiOx layer on polylactic acid (PLA)-based films to prepare SiOx/PLA coated films by plasma-enhanced chemical vapour deposition. Additionally, we compared PLA-based films and SiOx/PLA coated films in terms of the migration of different antioxidants (e.g. t-butylhydroquinone [TBHQ], butylated hydroxyanisole [BHA], and butylated hydroxytoluene [BHT]) via specific migration experiments and then investigated the effects of a SiOx layer on antioxidant migration under different conditions. The results indicate that antioxidant migration from SiOx/PLA coated films is similar to that for PLA-based films: with increase of temperature, decrease of food simulant polarity, and increase of single-sided contact time, the antioxidant migration rate and amount in SiOx/PLA coated films increase. The SiOx barrier layer significantly reduced the amount of migration of antioxidants with small and similar molecular weights and similar physical and chemical properties, while the degree of migration blocking was not significantly different among the studied antioxidants. However, the migration was affected by temperature and food simulant. Depending on the food simulants considered, the migration amount in SiOx/PLA coated films was reduced compared with that in PLA-based films by 42–46%, 44–47%, and 44–46% for TBHQ, BHA, and BHT, respectively.
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