Structural Control of SiOx Coatings and their Migration-Resistance Properties

Diethylhexyl phthalate (DEHP) is a kind of plasticizers which is generally used in plastics packaging materials to provide the flexibility. Especially in PVC films, a large amount of DEHP used makes it possibility of the widespread usage of PVC in the fresh food packaging market. But recent researches proved that DEHP can be easily migration into food and food stimulant. It causes reproductive disorders, mutation, carcinogenicity, and other genetic toxicity to all mammals. Hence blocking the migration of DEHP from the plastic to the foods becomes very important issue for the food safety. In this work, the migration kinetics of DEHP was explored. We achieved that the migration of DEHP can be well controlled through coated nano-scale SiOx barrier layer on the surface of PVC films, and the plasma enhanced chemical vapor deposition (PECVD) process is a very efficient way to prepare SiOx coatings on the plastic surface. It is also noticed that there is a relationship between the migration-resistance properties and coating structure through Fourier transform infrared spectroscopy (FTIR) for the chemical composition analysis, scanning electron microscope (SEM) for the topography investigation of the coating surfaces, surface profilemeter for the thickness measurement of coatings, and high-performance liquid chromatography (HPLC) for the barrier property evaluation of coatings at last. We conclude that the coatings can perfectly block the migration of the DEHP from plastics to their contents. When the deposition conditions of SiOx coatings were optimized, i.e. 50W of the discharge power, 4:1 of ratio of O2: HMDSO, and ca.100 nm thickness of SiOx, the 71.2% DEHP, compared to the control PVC film, was effectively barriered.