Wear of cryo-treated engineering polymers and composites

Abstract

Polymers and composites are extensively used in wear situations dominated by various types of abrasive mechanisms. Incorporation of,heat treatment and surface engineering by various chemical and physical techniques have been successfully employed to enhance wear behavior of metals as well as non-metals. In the case of metals, cryo-treatment is an emerging technique for improving wear resistance. However, this tool has not been applied for polymeric materials. Hence, in this paper investigations on the influence of cryo-treatment on wear performance of a series of thermoplastic engineering polymers such as Polyimide PI , Polyetherimide PEI ,Polytetrafluoroethylene PTFE , Polycarbonate PC and Polyurethane PU are presented. A series of composites of PI, PEI and its copolymer with increasing amount of short glass fiber and solid lubricants was also investigated. The selected materials were cryogenically treated at liquid nitrogen temperature for 24 h. Abrasive wear performance was evaluated at ambient temperature for a single pass on a pin-on-disc machine using Silicon Carbide SiC paper as a counterface. Comparison of wear rates of treated and untreated samples under various loads revealed that this technique has potential to increase the wear resistance of some polymers and composites. Fiber loading higher than 20%, however, showed deterioration in wear after cryo-treatment. The extent of influence of cryo-treatment on wear resistance depended on the type of base matrix and the nature and amount of fibre or particulate filler. Changes in crystallinity and hardness were studied and correlated with observed wear behavior. Scanning electron microscopy SEM was used to investigate changes in morphology due to cryo-treatment.