Ca²⁺ assisted enhancement of CNT/PEEK interfacial bonding and its conductive composites preparation and performance study

Polyether ether ketone (PEEK) is a high-performance engineering polymer that has garnered attention from researchers because of its remarkable specific strength, good corrosion resistance, and high temperature resistance. However, its insulating qualities restrict its use in applications like electromagnetic absorption, anti-static, and sensing applications. CNT reinforcement has been acknowledged as a successful technique for concurrently enhancing the mechanical properties and electrical conductivity of PEEK. Nevertheless, because of the high inertness of the PEEK and CNT surfaces as well as the different dispersing systems, it is difficult to disperse CNT in the PEEK matrix. This has a significant negative effect on the performance of CNT/PEEK composites. Based on this, in this study, ethanol-deionized water binary solvent was used to improve the dispersion of acidified CNT (aCNT) and PEEK powders. Calcium ion (Ca²⁺) was then used as an intermediate to bridge aCNT and PEEK to prepare aCNT-Ca²⁺/PEEK composite powders, which were then hot-pressed to produce highly conductive, mechanically enhanced aCNT/PEEK composites. FTIR, XPS, and Zeta potential experiments were used to thoroughly analyze the mechanism of Ca²⁺ bridging PEEK with aCNT. The findings demonstrate that, with the addition of Ca²⁺, aCNT can uniformly adsorb on the surface of PEEK, which produces a composite powder with a core-shell structure. By hot pressing this composite powder, a multi-channel three-dimensional conductive network may be produced. The obtained composite exhibits a conductivity of 9.9×10⁻⁴ S/cm at the conductive percolation threshold of 1.5 wt%, which is over 12 orders of magnitude higher than the conductivity of pure PEEK resin; the conductivity increased to 3.5 × 10⁻² S/cm at a 5 wt% aCNT concentration. The composites reached their maximum tensile strength of 92.87 MPa at a 1 wt% filler, a 15.7% increase over the pure PEEK resin. Furthermore, the conductive composite exhibits good temperature-sensitivity qualities, and its temperature-conductivity paths remain consistent across different heating methods and multiple heating processes, demonstrating stable sensing characteristics. Therefore, the aCNT-Ca²⁺/PEEK composites show great promise in temperature sensing, mechanical enhancement, and electrical conductivity.