Frictional properties of branched polyethylene I. The true area of contact

Abstract

Using a specially designed apparatus the friction and apparent area of contact between a hemispherical polymeric specimen and a glass flat were measured under various loads. The results show that the decrease in the coefficient of friction with increase of normal load cannot be explained by the use of the Hertz equation to describe the variation of the contact area with load even when the equation is modified to allow for the non-linearities of polymer mechanical behaviour. Factors which make the prediction of contact area as a function of load more complex are discussed.