Nitrile-butyl rubber like materials  were coated with amorphous hydrogenated diamond-like carbon (DLC)  coatings inorder to modify their surface and tribological properties. Measurements of water contact angle were performed by the sessile drop method and showed that the coated samples are more hydrophobic with water contact angles up to 1161. The surface free energy of the elastomer was calculated by the acid base regression method considering polar and dispersive contributions and the results were correlated with changes in the surface chemistry measured by X- ray photoelectron spectroscopy. It has been found that the lower presence of oxygen functional groups on the elastomer surfaces led to lower surface free energies, even though the polar contribution was not predominant. We also found that the DLC coatings led to a significant decrease of the surface free energy (upto16%) and that there is a good correlation between the surface free energy values and the corresponding water contact angle values. The coefficient of friction was also measured and presented a significant decrease after coating with DLC.

Keywords: Elastomer    Diamond-like coating   Surface energy  X-rayphoto electron spectroscopy Friction coefficient