The Influence of Mechanically Activated Kaolinite and Magnesium Spinel on Tribological Properties and Structure of PTFE Friction Surfaces

This article investigates the influence of mechanically activated kaolinite and magnesium spinel on tribological properties and structure of polytetrafluoroethylene (PTFE). The content of the fillers in a polymer matrix has been varied from 1 to 5 wt %. It has been established that combined addition of the fillers into PTFE results in an increase in wear resistance by 1125 times with respect to the initial polymer. It has been detected that combined addition of kaolinite with magnesium spinel leads to a decrease in sizes of secondary structures and absence of microcracks. It has been demonstrated that a magnesium spinel, being an active nanodisperse filler, actively participates in tribochemical processes and formation of a boundary layer. IR spectra of samples after friction contain absorption bands related to tribo-oxidation products, such as hydroxy groups and salts of carboxylic acids. It has been established that filling PTFE with mineral layered silicates promotes formation of transferred film on friction surfaces with the effect of a solid lubricant formed from transferred particles and oxidized structures of a polymer composite. Displacement of segments of layered structures to a wear composite surface with subsequent exfoliation has been detected. Therefore, the transferred film formed during friction and a secondary structure on composite surface facilitated sliding of the material. The developed materials can be used on friction units of machinery as components of pneumatic, hydraulic, and fuel systems in the North.