Investigation of the tribochemical and physico-mechanical processes in sliding of mineral-filled formaldehyde copolymer composites against steel

The effect of the treatment of the mineral fillers travertine, bentonite and tuff by organic lubricating materials on the structure and tribological properties of polymer composites was studied. The composites were made with these fillers and the formaldehyde based copolymer. They exhibited higher wear-resistance, improved strength properties and decreased coefficient of friction. The thermo-gravimetric, thermo-mechanical and sol–gel analyses indicated higher thermostability and improved elastic–viscous properties of the composites. The electron paramagnetic resonance spectroscopy confirmed the formation of intermolecular chemical bonds between polymer chains, which contributed to the increase in stiffness of the filled composite as a consequence of the formation of reticular structure. The analysis of transfer films formed on steel counterfaces by secondary-ion mass-spectrometry indicated thermo- and tribocracking of composites because of the depolymerization of polymer chain and the formation of low-molecular fractions. The modified mineral fillers contributed to the decrease in the rate of tribodestruction of basic copolymer chain by retarding the active oxidation of friction surfaces. Because of these processes, the increase in wear-resistance and the decrease in the coefficient of friction were obtained.