Chemically modified PTFE particles as solid lubricant additive for the fixation on substrate surfaces

Authors

• Thorsten Hoffmann Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Hohe Str. 06, Germany
• D Lehmann Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Hohe Str. 06, Germany
• M Anders Institut für Technische Logistik und Arbeitssysteme, Fakultät Maschinenwesen, Technische Universität Dresden, Germany
• T Schmidt Institut für Technische Logistik und Arbeitssysteme, Fakultät Maschinenwesen, Technische Universität Dresden, Germany
• T Heinze Institut für Fördertechnik und Kunststoffe, Fakultät Maschinenbau, Technische Universität Chemnitz, Germany
• M Michael Institut für Fördertechnik und Kunststoffe, Fakultät Maschinenbau, Technische Universität Chemnitz, Germany

Keywords:

PTFE, high performance lubricant, oil-PTFE-cc dispersion

Abstract

During the irradiation of high molecular weight poly(tetrafluoroethylene) (PTFE) in presence of oxygen perfluoroalkyl(peroxy) radicals and functional groups are formed which allow chemical coupling reactions (cc = chemical compatibilized) with oils and plastics. Contrary to the well-known inert properties of perfluorinated organic compounds high-effective additives can be produced by radiation modification and subsequent chemical compatibilization of such substances with olefinically unsaturated groups of oils/lubricants. By the irradiation process high molecular weight PTFE degrades by C-C and C-F bond scission to lower molecular weight PTFE microparticles which possess perfluoroalkyl(peroxy) radicals. These radicals are used for the chemical compatibilization reaction with olefinically unsaturated groups base oils. The tribological properties and the dispersion stability of the resulting oil-PTFE-cc (cc = chemical compatibilized) dispersions are significantly enhanced in comparison to physical mixture of oil and PTFE micropowder. These oil-PTFE-cc-dispersions show primarily anti-wear (AW) properties. The use of reactive groups (e.g. phosphite groups) in the oil gives the dispersions extreme pressure (EP) properties additionally. This article demonstrates the usefulness of the oil-PTFE-cc-dispersions in rolling bearings using phosphite-modified PTFE products as additive in lubricants (FE-8 test). The investigations are completed by the examination of roller elements by SEM/EDX analysis. A model is shown to explain the effect of phosphite groups on oxidic/hydrolytic metal surfaces.