High Performance Polymer Composites for Tribosystems in Hydrogen Environment

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Aim of the proposed research project is testing of polymer composite materials based on polyether ether ketone (PEEK) and polyimide (PI) for their suitability for tribosystems running in gaseous and liquid hydrogen. Because of its outstanding mechanical properties PEEK is to be used for frictionally stressed components and is already employed as a replacement for metallic materials in many applications. Compared to PEEK, PI is applicable in a wider temperature range and therefore, it will be included into the investigations. As solid lubricant various contents of natural or synthetic graphite will be admixed to the polymers. In a later phase of the project optimization of the materials by addition of carbon nanotubes and/or nanoparticles planned. Because hydrogen containing components are occasionally exposed to air and, because of safety reasons, have to be inertised before air inlet, a reliable function also in air and inert gases such as nitrogen belong to the requirements for frictionally stressed components. Therefore, also tests in air and, substitutional for inert environment, in vacuum will be carried out.The friction and wear data will be obtained by means of model test configurations in sliding friction against bearing steel and austenitic stainless steel. The frictional behavior of the polymers and also of graphite is considerably influenced by the environmental medium. Therefore, special attention will be paid to changes of friction mechanisms between different environments and tribochemical reactions in hydrogen environment. For this purpose, the topography and chemical composition of the friction surfaces and, if applicable, the transfer films will be investigated. Furthermore, also in view of applications with high purity requirements for the H2 gas, the outgasing behavior and creation of wear debris will be investigated. Under certain circumstances, reactive wear debris may even act as an ignition source.