Effect of thermal oxygen aging on the crystallization and insulation properties of polyether ether ketone

As an engineering material, polyether ether ketone (PEEK) has been widely used in many fields. It is important to study its thermal oxidative aging law for its material service optimization. The changes of chemical structure and relative properties of PEEK sheets after thermal oxygen aging at 280°C for different times were measured by universal tensile machine, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and resistance meter. The results showed that the elongation at break of the aged samples decreased with the extension of thermal aging time, while the tensile strength continuously increased within 336 h of thermal aging and then decreased gradually. Moreover, the crystallization temperature, melting enthalpy, and crystallinity of the samples decreased with the increase of thermal aging time. The crystallinity decreased to 2.3% after 2852 h aging and the initial decomposition temperature and the maximum decomposition temperature of PEEK gradually decreased from 554.3 to 523.5°C and 572.9 to 558.2°C, respectively. The increase of tan δ was more significant in the low frequency band (10−2–101) Hz. With the increase of aging time, the zeta potential of PEEK surface constantly moved to the negative direction and the volume resistivity and the dielectric strength similarly increased first and then decreased.