Effect of SiO x layer on preventing the migration of plasticizer and antioxidant from polyethylene terephthalate films

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 SiOx layer was deposited by plasma-enhanced chemical vapor deposition (PECVD) on a PET substrate to prepare a composite film. The effects of SiOx 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 SiOx-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 SiOx/PET composite film, while that of Irganox 1010 can reach 82.61%. For a fixed SiOx 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 SiOx 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 SiOx layer can block the migration of additives.