ADHESION ASSESSMENT OF DLC FILMS ON PET USING A SIMPLE TENSILE TESTER- COMPARISON OF DIFFERENT THEORIES

The adhesion of Diamond-Like Carbon (DLC) films on Poly(ethylenetereph thalate) (PET) sheet has been characterised by tensile testing, using simple equipment. Three theoretical analyses of the tensile test are d escribed, and their validity has been studied by calculating in three different ways the adhesion of the same samples (DLC on PET). The theo retically predicted adhesion from the longitudinal strain required for coating debonding did not appear to be an appropriate indicator for c oatings on polymers. An approach consisting of measuring either the mi nimum or the maximum crack spacing led to results which were more cons istent with the literature. The adhesion of DLC films on PET has been increased by a factor of 1.8 when a 5 min argon plasma treatment is ap plied prior to deposition. Although quantitative results have to be co nsidered with caution, this method is a simple and quick means of obta ining semi-quantitative results.