Tribological properties of aged nitrile butadiene rubber under dry sliding conditions

Nitrile Butadiene Rubber (NBR) is a polymer material and is widely used to make rubber-moving components in industrial applications. Ageing is an important factor that affects the friction and wear properties of the material. This study is aimed at investigating the tribological properties of NBR and how they are affected by ageing. The shore hardness, tensile strength and tear strength of normal and aged NBR samples were measured. A CBZ-1 tribo-tester was then used to conduct sliding wear tests between NBR pins and 1Cr18Ni9Ti stainless steel discs under dry sliding conditions. The surface morphologies of the worn NBR pins were examined using laser-interference profilometry and scanning electron microscopy. Also, the friction coefficients and wear rates were analysed and compared. The results showed that ageing had a significant effect on the mechanical and tribological properties of the NBR specimens. As the ageing time and temperature increased, the friction coefficient and the shore hardness also increased. Furthermore, accelerated ageing promoted the ageing process of NBR material, which resulted in a reduction in the tensile strength and tear strength of the NBR, along with the deterioration of its wear resistance. Consequently, its wear mass losses increased with the ageing process. The main wear mechanism between the rubbing pairs was found to be fatigue wear under dry conditions. The knowledge gained herein provides a better understanding of the material degradation and wear mechanism associated with ageing, and is useful for designing and selecting proper operation conditions for prolonged applications of the material under extreme circumstances. (C) 2014 Elsevier B.V. All rights reserved.