Synergy in tribological properties of polyamide 6 containing aramid pulp and irradiated polytetrafluoroethylene hybrid additives

Abstract

Tribological properties of polyamide 6 were improved synergistically using aramid pulp and irradiated polytetrafluoroethylene (IR-PTFE) hybrid additives. Tribological properties, i.e., coefficient of friction (COF) and wear rate (WR), were measured on a metallic plate using an in-house tribometer testing machine. Aramid pulp improved WR of the neat polyamide 6 by 75%, and IR-PTFE improved COF of the neat polymer by 47%, separately. However, the composite containing hybrid additives improved WR by 82% and COF by 56%, simultaneously. The analysis of COF curves during the test showed improved stability and smoothness of the friction test for the hybrid composite compared to neat polymer or composites containing individual additives. This suggests a synergistic mechanism for the hybrid composite due to some interactions between aramid pulp and IR-PTFE at the interface. However, no synergy was observed in some bulk properties of the hybrid composite, such as yield stress, tensile modulus, and heat distortion temperature. In order to explain the source of synergy just in the tribological properties of the hybrid composite, optical microscopic images of the metallic surface and Fourier transform infrared analysis of transfer films formed on the metallic surface were carried out. A mechanism explaining the formation of a uniform and stable transfer film containing the aramid pulp was proposed for the synergy observed in the hybrid composite.