Avaliação tribológica de compostos de politetrafluoretileno em ensaio de desgaste tipo mancal sobre eixo sem lubrificação

Abstract

This study examined the polytetrafluoroethylene (PTFE), a polymer widely used in tribological applications, with two types of filling, bronze and graphite, in order to verify the tribological performance and compare with pure PTFE. It is known that PTFE is a polymer which has a high versatility of use in various areas, taking a combination of chemical and mechanical properties, such as its low friction coefficient, makes it interesting for use as a sliding bearing. Thus was made a literature review in order to increase knowledge of polymeric materials and their fillers, and the parameters that could influence the friction and wear of these materials. Thus, long-term studies was made in the surfaces and Contact Laboratory (LASC) UTFPR to study the coefficient of kinetic friction, temperature in contact, check the wear and surface topography. Assays were performed with a stainless steel metal shaft coupled to a motor slid onto a polymeric bushing, simulating the use of fillers such as PTFE plain bearings. Five replicates were performed for four predefined conditions for each material. Afforded the temperature coefficients of friction and the contact to such conditions. Pre- and post testing of surfaces in contact were made through interferometry tools of white light, scanning electron microscopy and light microscopy. PTFE filled with graphite had the lowest coefficient of friction and low wear surface. Regarding the temperature in contact, for high speed and low normal load, we obtain the lowest value for PTFE with bronze filler, as for low speed and high normal load pure PTFE is what achieved lower temperature.