Comparative study on the mechanical, tribological, and thermal properties of POM composites filled with different PTFE

Abstract

In this study, two different types of polytetrafluoroethylene (PTFE) fillers (i.e. fibrillar and particulate PTFE) were utilized to improve the tribological properties of polyoxymethylene (POM). POM/PTFE composites with various filler contents were tested on a commercial block-on-ring tester. To further probe the tribological properties of POM/PTFE composites under severe sliding conditions, a homemade pin-on-disc tester was employed. Results showed that the lowest coefficient of friction and wear rate are obtained from PTFE particle–filled POM composites at 20 wt%, which is attributed to the formation of uniform transfer film at the sliding interface thanks to the well distribution of PTFE particles. The mass wear rate of POM/PTFE fiber composites is lower than that of PTFE particle–containing counterparts due to the better load transfer of high aspect ratio fibers. The tensile properties of POM/PTFE composites deteriorate with the addition of PTFE fillers; however, the impact strength is significantly enhanced for PTFE fiber filled POM composites. Moreover, both the melting and crystallization properties of POM are affected by the morphology of PTFE fillers and filler concentration, as characterized by differential scanning calorimetry analysis.

Effect of carbon fiber addition on the tribological properties of polyoxymethylene composites

“…According to a previous study, [37] POM composites filled with 20 wt% PTFE powders (i.e., PP) exhibited optimum tribological performance whereas samples with 20 wt% PTFE fibers (i.e., PF) showed reduced mass wear rate, especially under high P Â V conditions. Nevertheless, samples with 20 wt% PTFE demonstrated the best friction and wear properties.…”

“…Unlike low P Â V conditions, the μ of POM decreased significantly with the addition of PP, that is PTFE particle, which was related to the formation of transfer film at the steel counterpart. [29,37] In general, the μ of CF filled POM/PP composites decreased with sliding time when the content of CF was 5 wt%, regardless of the types of CFs. It could be anticipated that the mechanical properties of POM/PP blends were enhanced with the presence of CFs, which was advantageous to improve the tribological properties under severe sliding conditions.…”

“…[32,47] On the other hand, the presence of a large number of MCF grains exacerbated plowing effect on the sliding surface of testing specimens. [37] Both factors were thought to be responsible for the changes of friction behavior of POM/PF/MCF composites with increasing MCF content.…”

“…We also found that the addition of PTFE particles was more advantageous to reduce the friction coefficient, and the presence of PTFE fibers significantly improved the impact strength of POM. [37] However, several studies have reported that a reduction of friction coefficient and an increase of wear resistance was observed with the incorporation of CFs, [21,24,38] whereas in some other work, both the friction coefficient and wear resistance decreased with the presence of CFs. [23,29] It should be noted that the length of fibers played a key role in determining the tribological properties of polymer composites.…”

Green recycling of aramid fiber waste as the friction modifier of POM by solid state shear milling technology

“…It can be seen that there was a significant decline in the transient COF of all samples at the initial sliding state, because of the unstable interface between the steel ring and samples. 44,51,52 After that, the COF values tended to reach some constants. However, as for the pure POM, the COF values fluctuated greatly, resulting from the melting or softening of POM due to a strong thermal effect generated during the sliding process.…”