Physical structure and architecture evolution of PEEK under proton irradiation: Comparison with electron irradiation

Orbiting satellites operate in a hostile environment characterized by a high vacuum of the order of 10 −11 mbar, thermal cycling and particle irradiation. This study focusses on proton irradiation and their effects on the physical properties of poly(ether-ether-ketone) (PEEK). It is a high-performance thermoplastic, commonly used in space industry because of its low outgassing and good resistance to irradiations. 8 μ m PEEK films were irradiated with 1 MeV protons to avoid any possible implantation and to obtain an homogeneous dose in the thickness. Four doses representative of the lifetime of a satellite in GEOstationary (GEO) orbit were carried out. Analysis of the physico-chemical structure revealed two main phenomena after irradiation : amorphization and crosslinking. The study of molecular mobility confirmed these evolutions. Correlation of the different analysis techniques highlighted a change in behaviour from 50 MGy : crosslinking prevails over amorphization and chain scission. Then, new pristine samples were irradiated with electrons at equivalent doses. The comparison showed no major difference between proton-irradiated and electron-irradiated PEEK, except crytsallization. Indeed, proton irradiation leads to a higher decrease of crystallization temperature and crystallinity degree that can be due to the creation of a greater number of defects in the crystalline phase. • Amorphization and crosslinking are the main phenomena observed after irradiation. • BDS allowed the study of molecular mobility and charge transport. • Scenarios for crosslinking and chain scission were proposed using XPS analysis. • All analysis techniques used showed a change in behavior from 50 MGy. • DSC tests showed no major changes between electron and proton irradiation.