Tribological Performance of PTFE-based Coating Modified with Microencapsulated [HMIM][NTf2] Ionic Liquid

In this work, a PTFE-based self-lubricating coating containing microencapsulated [HMIM][NTf2] ionic liquid (IL) lubricant is reported. The microcapsules, made of polysulphone, are prepared by solvent evaporation. In order to allow incorporation in the thin PTFE coating layer, which is applied by spraying, the capsules were produced with small sizes (below 10 μm). Their physico-chemical characterization is presented in terms of SEM/EDS, TGA, FTIR and particle size distribution analysis. It is shown that both the encapsulant material and the IL lubricant are able to withstand the high-temperature curing conditions necessary for the coating system used (380 °C during 30 min). Crossed-cylinders tribological testing of the applied coatings showed that incorporation of IL-containing capsules yields a reduction in coefficient of friction of up to 12 % when compared to the baseline formulation and a reduction of up to 70 % in wear rate under high load and low sliding speed conditions. The tribological behaviour of the modified coating is further assessed in different load and speed (P.V) combinations.