Study of damaged depth profiles of ion-irradiated PEEK

Thermal neutron depth profiling (TNDP) was used for the study of the free radical distribution in ion-irradiated poly-aryl-ether-ether ketone (PEEK). The thin PEEK film was irradiated by the 2 MeV O+ ions up to the fluence 6 × 1014 ions/cm2. The depth profiles of the free radicals in the ion-modified PEEK were traced by the Li+ ions incorporated to a damaged area of PEEK by exposing the sample to a 5 mol water solution of LiCl. The depth distributions of the free radicals in the inspected PEEK specimens were found fractioned (for higher fluences) into two distinct parts that followed both electronic and nuclear transfer energy distributions (predicted by the TRIM code). The Li decoration – TNDP was also applied for the study of the free radical depth profile evolution induced by the thermal processing of the samples in vacuum. The evolution was studied in a broad range of temperatures from RT to the melting point of the polymer. The thermal annealing led to a process of gradual redistribution and annihilation of the free radicals. This process was dramatically enhanced, especially at elevated temperatures around and above the glass transition point of PEEK.