TRIBOCHEMICAL REACTIONS ON THE SURFACES OF THIN-FILM MAGNETIC MEDIA

An experimental study has been performed regarding the effect of extreme pressure (EP) additives on minimizing friction in order to achieve the required frictional properties of thin film magnetic media. In shuttling motion, disulfide additives had no effect on friction, due to their inability to form a protective film. While alkyl phosphite changed the surface to phosphate film and reduced the coefficient of friction, aryl phosphite was less effective because of the steric hindrance of the aromatic ring generated by hydrolysis. Together with the results of the enthalpy of preferential adsorption measurements, it was concluded that the effectiveness of alkyl phosphite as an EP additive depended on the formation of a protective film on the rubbing surface and on the strength with which the lubricant anchored to the outermost phosphate surface. Based on these findings, a combination of alkyl phosphite and the ester lubricant exhibited further improved performance for magnetic thin film media.