Modification of rubber surface with hydrogenated diamond-like carbon thin films

Thin films of hydrogenated diamond-like carbon (DLC) have been deposited on hydrogenated nitrile butadiene rubber (HNBR) for reduction of friction and enhancement of wear resistance of dynamic rubber seals, by sputtering graphite targets in C(2)H(2)/Ar plasma. The wax removal and pre-deposition plasma treatment are proven to be crucial and effective for the improvement of film performance due to enhanced adhesion. The columnar structure and the crack network formed during deposition enhance the flexibility of DLC thin films and exhibit strain tolerance up to 5%. After stretched to 50% strain and being unloaded from the strained status, thin DLC films of similar to 300 nm thickness still adhere very well on the rubber substrates and no spallation or delamination has been observed. The optimized DLC thin film on plasma treated HNBR rubber exhibits very low coefficient of friction of 0.19 (compared to > 1 of uncoated HNBR rubber) at high normal load of 3 N and after being stretched to 50% strain.