The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles

To reduce the oxygen transmission rate through apolyethylene terephthalate (PET) bottle (an organic plastic)diamond-like carbon (DLC) coatings on the inner surface of the PETbottle were deposited by radio frequency plasma-enhanced chemicalvapour deposition (RF-PECVD) technology with C₂H₂ as thesource of carbon and Ar as the diluted gas. As the barrier layer tohumidity and gas permeation, this paper analyses the DLC filmstructure, composition, morphology and barrier properties by Fouriertransform infrared, atomic force microscopy, scanning electronmicroscopy and oxygen transmission rate in detail. From thespectrum, it is found that the DLC film mainly consists ofsp³ bonds. The barrier property of the films is significantlyrelevant to the sp³ bond concentration in the coating, the filmthickness and morphology. Additionally, it is found that DLC filmdeposited in an inductively coupled plasma enhanced capacitivelycoupled plasma source shows a compact, homogeneous and crack-freesurface, which is beneficial for a good gas barrier property in PETbottles.