Surface analysis of NBR and HNBR elastomers modified with different plasma treatments

In this work, three rubber-like materials (NBR 7201, NBR 9003 and HNBR 8001) with applications in the automotive industry were studied. Different atmospheric pressure plasma treatments were used to modify the surface properties of these materials in order to improve their tribological behaviour. Surface analyses of the samples by means of X-ray photoelectron spectroscopy (XPS) were performed in order to get information about the surface chemistry and the elemental composition of the contact surfaces. In addition, wetting experiments were also carried out by measuring the contact angle of water drops on the surfaces using the sessile drop method. The XPS results showed a modification of the surface composition in both NBR rubbers, mainly due to an increase in the oxygen content, while the same treatments produced only slight modifications on the surface composition of the HNBR. The combination of N2 and CH3COOH during the plasma operation produced the strongest modifications of the surface composition of the tested elastomers. All these surface modifications also produced a change in the wetting of the rubber-like materials. The results revealed that the plasma treatments modified the hydrophobicity of the rubber-like NBRs.