Influence of yield strength and toughness on friction and wear of polycarbonate

Polycarbonate was chosen as a model material to study the influence of yield strength and toughness on the tribological behaviour of the polymer. Yield stress and toughness of polycarbonate were varied by controlled physical ageing or by mechanical or thermal rejuvenation. The yield stress ranged from about 40 MPa for mechanically rejuvenated to 70 MPa for annealed polycarbonate. The area under the stress-strain curve is considered to be a measure for the toughness. The strain-to-break decreases with physical ageing, which results in a decrease of the toughness of the polymer. It was shown that yield strength and toughness did not affect friction and abrasive wear of polycarbonate under several different test conditions. These findings are compared with the usual views in literature upon friction and wear of polymers. There are strong indications that the polymer network of polycarbonate plays an important role in the wear resistance. However, no wear improvement was found with an increase in molecular weight in the range of polycarbonates studied.