The effects on polyetheretherketone and polyethersulfone of electron and gamma irradiation

In this study, the effects of ionizing radiation on the aromatic polymers p olyethersulfone (PES) and polyetheretherketone (PEEK) were investigated. UV light, gamma rays and a high-energy electron beam were used as radiation s ources. A range of techniques has been utilized to investigate changes in P ES and PEEK as a result of exposure to these sources, electron spin resonan ce (ESR) measurements showed the creation of radicals in PES by UV or gamma radiation. These radicals decayed, but some were still present 24 h after irradiation at room temperature. In PEEK, radicals were formed as a result of UV at room temperature and by UV or gamma irradiation at 77 K. After irr adiation at room temperature, these radicals decayed totally within 24 h. U V-visible absorption measurements of FES samples showed a dose related chan ge at the absorption edge; no such change was observed for PEEK. Phosphores cence after gamma irradiation increased in intensity for PES at low tempera ture but decreased at higher temperatures. For PEEK, no such changes were o bserved after irradiation. The differential scanning calorimeter (DSC) meas urements showed changes in the crystallization, glass transition and melt-p oint temperatures of both PES and PEEK after electron irradiation. Electric al changes induced by irradiation were investigated using thermally stimula ted discharge current (TSDC) and low frequency dielectric responses, derive d from transient current (TC) measurements. Dielectric changes were observe d for PES exposed to either gamma rays or an electron beam. For PEEK only m inor changes in the TSDC spectrum were observed after exposure to gamma rad iation. More significant changes were observed after exposure to the electr on beam. Correlations were found between the production of radicals and the changes in the structural and electrical properties of the materials. Sinc e significant changes were observed in the dielectric spectra of PEEK and P ES at low frequencies, dielectric spectroscopy may provide a measure of agi ng in both insulation systems.