Oxygen diffusion barrier properties of transparent oxide coatings on polymeric substrates

Gas diffusion properties of transparent thin film coatings have been under investigation by a number of workers for application in food and medical packaging. Work on the oxygen permeation properties of high barrier thin film coatings is reviewed, with emphasis on the coating thickness dependence of the oxygen permeation rate. Comparison of the coating thickness dependence of the oxygen permeation properties of evaporated, sputtered and plasma-deposited transparent oxide and organic coatings suggests that the reduction in permeation due to the coatings is limited by transport through coating defects (e.g. pinholes, grain boundaries or microcracks). The usefulness of such measurements as a probe of coating microstructure is assessed by reviewing structural and permeation investigations of metallized coatings on polymers.