The effect of molecular orientation through uniaxial prestraining in poly(vinyl chloride) and polycarbonate on their friction and wear characteristics

Abstract

The mechanical and tribological properties of polymers generally depend on the exact details of their molecular arrangements, i.e. both their crystalline morphology and their molecular orientation, these being intimately related. The objective of this paper is to investigate experimentally the effect of uniaxial prestraining of specimens of poly(vinyl chloride) (PVC) and polycarbonate (PC) on their friction and wear characteristics. For this purpose tensile sheet specimens of PVC and PC were uniaxially stretched to varying final extensions, thus obtaining various degrees of molecular orientation and mechanical anisotropy. Short pins were subsequently cut from these deformed sheets and tested at a sliding speed of 27.5 cm s −1 and a moderate normal load of 49 N in an instrumented pin-on-disc friction and wear testing machine with stainless steel as the rotating disc material. Results obtained on the friction coefficient and wear rates for various samples are presented and correlations are made with uniaxial prestrain, mechanical energy to fracture and loss modulus.