Wear resistance of composite materials based on ultra-high molecular polyethylene with combined filling

Polymer composite materials (PCM) of antifriction duty with self-lubricating properties are used for the manufacture of various parts in friction units of machines and mechanisms. PCM can partially replace parts made of metals and alloys, increasing the reliability and service life of the equipment when the use of oils or external lubricants is limited or prohibited. The goal of the study is the effect of fillers (sulfenamide, sulfur, magnesium and zinc oxides) on the tribological parameters of polymer composite materials based on ultra-high molecular weight polyethylene (UHMWPE). Samples were prepared by hot pressing at a temperature of 175°C and a pressure of 10 MPa. Composites with filler concentrations 0.5 and 1 wt.% were considered (for sulfenamide, sulfenamide with sulfur, and combinations of 0.5 and 1 wt.% sulfenamide with sulfur and zinc oxide or magnesium oxide). It is shown that the introduction of sulfenamide leads to an increase in the wear resistance by six times, and the introduction of a combination of fillers of 0.5 wt.% sulfenamide, sulfur, and magnesium oxide — by 1.5 times. The friction surfaces of composites were studied using methods of scanning electron microscopy and IR-spectrometry. The formation of an oriented ordered structure in the form of clusters of wear products was revealed on the friction surfaces of composites filled with sulfenamide. In the case of combined filling, secondary structures were found on the friction surface, which visually differ from the UHMWPE friction surface. The appearance of peaks in IR spectra corresponding to oxygen-containing groups (–C=O, –COOX) was observed on the friction surface of composites with combined filling. It is shown that IR spectra of composites with mono- and binary fillers have peaks of less intensity due to the formation of secondary structures. The introduction of sulfenamide into UHMWPE, together with zinc and magnesium oxides, promotes the crosslinking of polymer macromolecules in the friction zone due to frictional heating, shear loads, and the action of a counterbody. The developed materials can be used as parts of friction units for cars and transport equipment that can withstand harsh operating conditions in a sharply continental climate.