The Application of Nano-SiOx Coatings as Migration Resistance Layer by Plasma Enhanced Chemical Vapor Deposition

Accumulative intake of plasticizers that are generally used to produce flexibility of webs in plastics has been proven to cause reproductive system problems and women's infertility, and long-term consumption may even cause cancer. Hence a nano-scale layer, named as functional barrier layer, was deposited on the plastic surface to prevent plasticizer diethylhexyl phthalate (DEHP) migration from food-contact materials to foods. The feasibility of a functional barrier layer, i.e. SiOx coating through plasma enhanced chemical vapor deposition process was then described in this paper. In this research we used Fourier transform infrared spectroscope to analyze the chemical composition of the coatings, scanning electron microscope to explore the topography of the coating surfaces, surface profilemeter to measure coating thickness in plastics, and high-performance liquid chromatography to evaluate the barrier properties of coatings. The results have clearly shown that the coatings can perfectly block the migration of the DEHP from plastics to their containers. It is to be noted that process parameters had a critical influence on the block properties of coatings. When the deposition conditions of SiOx coatings were optimized, i.e. the discharge power of 50 W, 4:1 of O-2: HMDSO ratio and the thickness of 100 nm, the 71.2 % DEHP was effectively blocked in the plastic film.