Comparison and analysis of measurements for crystallinity of PEEK and CF/PEEK composites

Abstract PEEK and CF/PEEK are two significant materials whose properties are intricately linked to their crystallization behavior. This study employed three analytical techniques—density method, differential scanning calorimetry (DSC), and x‐ray diffraction (XRD)—to explore and quantify the crystallinity of Poly (ether ether ketone) (PEEK) and its composites. Thermogravimetric analysis was used to determine the resin content of the composites, which is essential for the density and DSC methods. The density method, based on Archimedes' principle, calculated both mass and volume crystallinity. DSC assessed crystallinity by analyzing differences in melting enthalpy, while XRD determined crystallinity through diffraction patterns and peak analysis. The results demonstrate that these three techniques can be effectively utilized for calculating the crystallinity of PEEK and its composites. Using the density method, PEEK exhibited a crystallinity of (26.53 ± 1.30)% by mass and (24.57 ± 1.24)% by volume. The prepreg, CF/PEEK, and CF/PEEK‐AA1 composites showed enhanced crystallinity values. Crystallinity calculated by DSC was 29.16% for PEEK, 55.35% for prepreg, 55.48% for CF/PEEK, and 53.50% for CF/PEEK‐AA1. XRD results provided crystallinity values of 46.35% for PEEK, 63.20% for prepreg, 64.80% for CF/PEEK, and 66.57% for CF/PEEK‐AA1, along with detailed information about unit cells and crystal planes. This study contributes to a better understanding of these methods, paving the way for future refinement and integration, thereby improving the precision of crystallinity determination. Highlights Crystallinity study of PEEK and CF/PEEK composites by density, DSC and XRD methods. Crystallinity calculated by methods in different principles are irrelevant. Crystallinity estimated by density and DSC requires resin content. Information on crystal and crystallinity can be obtained by XRD independently. Crystallinity calculated by XRD is the highest. Results obtained by density and DSC method are close.