Flexible diamond-like carbon thin film coated rubbers: fundamentals and applications

Dynamic rubber seals are major sources of friction of lubrication systems and bearings, which may take up to 75% of the total friction. The solution we present is to coat rubbers with diamond-like carbon (DLC) thin film, by which the coefficient of friction is reduced to less than one tenth. Coating rubber is very challenging because the film must be flexible and strongly adhered to rubber surface. Here we present and discuss our novel approach by depositing flexible DLC films on various rubbers via self segmentation. By making use of the substantial thermal mismatch between DLC film and rubber substrates, a dense crack network forms in DLC films and contributes to flexibility. The formation mechanism of crack network and its effect on the flexibility and friction of DLC film coated rubbers are scrutinized with model prediction and experimental study. This lecture provides generic design rules for the deposition of flexible and ultra low friction DLC films on rubber seals.