Poly(ether ether ketone) (PEEK) is a high‐performance thermoplastic with a distinctive combination of corrosion resistance, thermo‐oxidative stability and outstanding physical and mechanical properties at high temperatures. A pertinent step forward in the development of this thermoplastic has been the inclusion of electrically conductive fillers to expand its functionality. In this review an overview of the research on electrically conductive PEEK composites is provided. Conductive filler type, fabrication methods, characterization details and different properties are described. Carbon nanotubes, graphene nanoplatelets and other organic and inorganic conductive fillers such as expanded graphite and nickel have been incorporated into PEEK by techniques such as extrusion, injection moulding and cold and hot compression moulding and in some cases with pre‐processing steps including mechanochemical modifications in organic solvents. The influences of type, loading and compatibilization of fillers and processing conditions on the mechanical and electrical conductivity properties of the composites are analysed and compared. The incorporated fillers have been able to enhance the electrical conductivity of the PEEK composites to either the semiconducting or conductive regions. PEEK composites containing carbon nanotubes compatibilized by polysulfones and poly(ether imide) achieved electrical conductivity values in the semiconducting region at the lowest electrical percolation threshold of 0.1 wt%. Additionally, the inclusion of 10 wt% expanded graphite and 10 vol% inorganic macroparticles of nickel noticeably improved the electrical conductivity of PEEK into the conductive region. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

In this study unfunctionalized expanded graphite (EG) was incorporated into poly(ether ether ketone) (PEEK) using twin‐screw extrusion and injection moulding to manufacture cost‐effective PEEK/EG composites for mass production of high‐performance antistatic materials. Direct current electrical conductivity, morphology, rheological and thermal properties of the composites were investigated. At an EG loading of 5 vol%, the electrical conductivity exhibited an abrupt increase to 1.45 × 10−5 S m−1 which was in the required range of electrical conductivity of antistatic materials. The frequency dependence of the storage modulus of the melt containing  2 vol% EG decreased significantly at low frequencies. Viscosity did not increase much with the addition of EG in comparison with other nanofillers such as carbon nanotubes. The crystallinity of PEEK increased to 41.11% from 35.87% upon addition of  3 vol% EG. EG improved the thermal stability of PEEK by an increase in the initiation temperature of its decomposition steps. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

In this work, antistatic, high-performance composites of poly (ether ether ketone) (PEEK) and concentrations of 0.5–7 vol% expanded graphite (EG) were fabricated via twin-screw extrusion and injection moulding at mould temperatures of 200°C. The morphological, electrical, rheological, thermal, mechanical, and wear properties of the composites were investigated. Scanning electron microscope (SEM) images indicate that distribution and dispersion of EG platelets in the PEEK matrix are enhanced at higher EG loadings. The electrical conductivity of the composites with 5 vol% of EG exhibits a sharp rise in the electrical conductivity range of antistatic materials because of the formation of conductive paths. The formation of a three-dimensional EG network led to a rapid increase in the storage modulus of the melt of the 2 vol% of EG-loaded composite at a frequency of 0.1 rad/s and temperature of 370°C. The neat PEEK and composites containing 0.5–5 vol% EG indicated a cold-crystallisation peak in the first heating scan of a non-isothermal differential scan calorimetry (DSC) test and their crystallinity degrees changed slightly. However, after removing their thermal and stress histories, the EG platelets promoted nucleation and increased the PEEK crystallinity remarkably, indicating that annealing of the PEEK composites can improve their mechanical performance. The neat PEEK exhibits the standard tensile and flexural stress-strain behaviour of thermoplastics, and the composites exhibit elastic behaviour initially followed by a weak plastic deformation before fracture. The addition of 5 vol% of EG to PEEK increased the tensile and flexural modulus from 3.84 and 3.55 GPa to 4.15 and 4.40 GPa, decreased the strength from 96.73 and 156.41 MPa to 62 and 118.19 MPa, and the elongation at break from 27.09 and 12.9% to 4 and 4.6%, respectively. The wear resistance of the composite containing 3 vol% EG was enhanced by 37% compared with the neat PEEK.