Special grade of graphite in NAO friction materials for possible replacement of copper

The main focus of current research in non-asbestos organic (NAO) friction materials (FMs) is on searching replacement of copper which is a recently proven hazard to the aquatic life. Cu is almost invariably used in the various forms in FMs mainly because it enhances thermal conductivity of a composite which helps to dissipate frictional heat efficiently from the friction surface and thus resists the negative impact on performance especially on fade. Moreover, it also acts as a solid lubricant at high temperature. The replacement is not easy and perhaps will have to be done by a package of ingredients. The search for newer ingredients hence is continuing. In this paper, newly commercialized graphite which is more conducting than the ordinary graphite is explored for possible replacement. During preliminary work presented in this paper, efforts were focussed on investigating the influence of amount of this graphite on tribo-properties. Three realistic composites containing all essential ingredients of FMs were developed which differed only in amount of new graphite (TG) (5%, 10% and 15%). The brake-shoes were tested against drum on chase machine as per IS 2742. Initial studies confirmed that 10% is the optimum amount of TG, where most of the performance properties were best. SEM studies were done to understand correlation between wear and wear mechanisms through topography studies.