The use of trans-vinylene formation in quantifying the spatial distribution of electron beam penetration in polyethylene. Single-sided, double-sided and shielded irradiation

The use of the quantification of trans-vinylene unsaturations in irradiated ultrahigh molecular weight polyethylene (UHMWPE) in determining the spatial distribution of electron beam penetration was investigated. UHMWPE was irradiated with a 10 MeV linear electron beam accelerator to 100 kGy at both room temperature and 125°C in air. The irradiation was carried out in shielded and unshielded single-sided and unshielded double-sided irradiation modes. Dose–depth profiles were measured by quantifying the yields of trans-vinylene unsaturations as a function of depth away from the e-beam incidence surfaces using infrared spectroscopy. The extent of beam penetration increased with increasing irradiation temperature as was manifested by the increase in the iso-dose penetration with the unshielded single-sided irradiation and increased dose overlap with the unshielded double-sided irradiation. The optimum thickness with maximum uniformity in dose–depth distribution for double-sided irradiation was 85 and 90 mm for 25°C and 125°C irradiation temperatures, respectively.