Flammability properties of PEEK and carbon nanotube composites

Aryl polyetheretherketones (PEEK) show remarkable thermal stability and low flammability, with an onset of decomposition at around 600 °C, and 60% char formation in the cone calorimeter at 60 kW m−2. However, at lower heat fluxes, and in other small-scale flammability tests, it is difficult to obtain consistent results. PEEK polymer has been modified with different types of carbon nanotubes (CNT), leading to modest improvements in the burning behaviour at addition levels between 0.1 and 1%. The characterisation of the composites indicated satisfactory dispersion, modest enhancements in mechanical properties and thermal stability, and reductions of peak heat release rate for the best performing formulations. Significant differences in thermal stability and burning behaviour were observed as a function of the nature of the CNTs, and the loading level within the polymer.