Poly(aryl ether ketone)\n(PAEK) with Both High Gel\nContent and High Crystallinity for High-Temperature Applications

Poly(ether ether ketone) (PEEK) is a semicrystalline\nengineering\nplastic with excellent characteristics. However, its modulus and dimensional\nstability decrease significantly above the glass transition temperature\n(<i>T</i><sub>g</sub>). In this paper, cross-linkable PAEK\n(DBPEEKs) with carbon–carbon double bonds was synthesized,\nand the majority of cross-linkable synthesis methods were determined\nby using the curing kinetics. By the introduction of biphenyl bisphenol\n(BP) as a rigid monomer unit, a series of cross-linkable crystalline\nPAEK (DPEDEKs) with strong cross-linking and crystallinity after curing\nwere generated. DPEDEK-25% after the curing process (DPEDEK-25%-gradient\ncuring) still maintained 24% crystallinity (<i>X</i><sub>c</sub>) at a gel content (<i>f</i>) of 96%. This coexistence\nof crystallization and cross-linking broadens the application range\nof PEEK at high temperatures. At 250 °C, DPEDEK-25%-gradient\ncuring had a tensile strength of 42 MPa, which was higher than that\nof the PEEK composite material 450GL30 at 275 °C and similar\nto that of 450CA30 (VICTREX official website). DPEDEK-25%-gradient\ncuring remained applicable at 300 °C, with a wear rate of 7.69\n× 10<sup>–7</sup> mm<sup>3</sup> N<sup>–1</sup> m<sup>–1</sup> and an average friction coefficient (COF)\nof 0.41. Whether at ambient or elevated temperatures, DPEDEK-25%-gradient\ncuring had the same solvent resistance as PEEK. This work provides\nimportant guidance for expanding the application scope of PEEK at\nhigh temperatures.