The Influence of Graphite Filler on the Self-Lubricating Properties of Epoxy Composites

Abstract

In this work, epoxy composites filled with flake graphite of various size (less than 10 μm and less than 45 μm) were produced. The aim of the research was to develop a self-lubricating material with favorable tribological properties, i.e., reduced friction coefficient compared to unfilled epoxy resin and limited abrasive wear. The research material was produced using technical epoxy resins based on bisphenol A. The detailed process of composite production was described, and typical technological problems were considered. The addition of graphite led to an increase in dynamic viscosity, which positively limits the phenomenon of sedimentation, but an increase in the filler content also led to an increase in the porosity of the material. A series of tests have shown that the addition of graphite above 5% by weight allows for a reduction in the friction coefficient from 0.6 to 0.4 and significantly reduces the material’s tendency to abrasive wear.

Tribological Properties of Composites Based on Single-Component Powdered Epoxy Matrix Filled with Graphite

“…The phenomenon of favorable carbon tribofilm formation is known from previous literature reports. In a previous article [40], it was shown that the addition of graphite, creating a carbon tribofilm on the composite surface, leads to reduction in the friction coefficient by over 30% and protects the material against rapid wear. Myalski, in publication [55], observed that carbon reinforcement (carbon foam) acting as a solid lubricant allows for the effective formation of a carbon tribofilm.…”

“…The test was carried out on a Shimadzu AGX-V testing machine (Shimadzu, Kyoto, Japan) with a distance between supports of 60 mm and a strain rate of 5 mm/min. Tribological tests under technically dry friction conditions were conducted using the pin-on-block method with the TM-01M tribotester [40,42]. The counterface material was a steel pin (KONTAKT S.A., Toru ń, Poland) measuring 6 mm in diameter (hardened carbon steel with a hardness of 60 ± 2 HRC, DIN 100Cr6).…”

“…The cross-section of the material allows for a uniform distribution of the graphite filler in all samples and no tendency to agglomeration of graphite particles. In the case of casting processes with liquid epoxy resins, there are known problems with obtaining a uniform distribution of powder fillers, mainly due to sedimentation occurring under the influence of gravity [40]. The production of composites using single-component epoxy powders allows for high material homogeneity because there is no intensive movement of fillers during production.…”

“…This article is a continuation of previous research conducted on self-lubricating epoxy composites with the addition of graphite fillers. The previous publication [40] discussed epoxy composites produced on the basis of typical liquid epoxy resins. In this publication, the liquid epoxy resin is replaced by a single-component epoxy in powder form.…”