Hydrogen Emission and Macromolecular Radiation-Induced Defects in Polyethylene Irradiated under an Inert Atmosphere: The Role of Energy Transfers toward trans-Vinylene Unsaturations

Abstract

This article is aimed at studying the evolution of H release as well as radiation-induced defects in polyethylene (PE), as a function of the irradiation dose under anoxic conditions. We analyze the influence of the energy transfers and trapping toward radiation-induced defects on the evolution of the radiation chemical yields with dose. One key objective herein is to quantify the contribution of these transfers toward trans-vinylene (TV) on H emission. For this purpose, pure PE was irradiated in a large dose domain and H emission was compared to that in predoped PEs containing chemically inserted TV groups irradiated at low doses. In parallel, evolutions of the concentrations of the TV groups and minor defects (vinyl and trans-trans-diene) as a function of dose were considered. Moreover, measuring simultaneously H and unsaturated groups had allowed inferring the cross-linking evolution with dose. With this methodology, we have succeeded in quantifying the efficiency of TVs and cross-links as energy traps and, using simple models, in fully describing the evolution of all of the radiation chemical yields. Besides, irradiations were performed using either low linear energy transfer irradiations (electron beams, γ rays) or ion beams, with the objective to assess the influence of the high ionization and excitation densities induced by the latter on PE ageing and energy transfer processes.

Microelectromechanical Transducer to Monitor High-Doses of Nuclear Irradiation

“…The higher the quantity of branches in PE, the lower the crystallinity. Unlike claims reported in some studies (e.g., [30,69]) it appears that the crystallinity degree of polyethylene has a weak impact on the hydrogen emission yield factor [33,70]. Crystallinity was not a discriminant parameter in the conditions of our application.…”

“…As the hydrogen emission yield factor is almost constant for low doses up to 200 kGy [ 30 ], the quantity of is directly proportional to the dose in this range. At room temperature and in an inert ( ) atmosphere, the decrease of factor occurs at higher doses due to the generation of C=C unsaturated bonds during the irradiation that acts as an energy sink [ 30 , 70 , 77 ]: energy and radicals transfer preferentially to these bonds, leading to undesirable reduction of release. For example in [ 70 ], the hydrogen emission yield factor during β irradiation at room temperature was of 4 × 10 −7 mol·J −1 at low dose level and only 2 × 10 −7 mol·J −1 at about 10 MGy.…”

“…At room temperature and in an inert ( ) atmosphere, the decrease of factor occurs at higher doses due to the generation of C=C unsaturated bonds during the irradiation that acts as an energy sink [ 30 , 70 , 77 ]: energy and radicals transfer preferentially to these bonds, leading to undesirable reduction of release. For example in [ 70 ], the hydrogen emission yield factor during β irradiation at room temperature was of 4 × 10 −7 mol·J −1 at low dose level and only 2 × 10 −7 mol·J −1 at about 10 MGy. Another example is reported in [ 30 ] where for the ultra-high molecular weight polyethylene (UHMWPE) during β irradiation (dose rate of 5 kGy/h) in vacuum and room atmosphere was 4.0 × 10 −7 mol·J −1 at 1kGy and only of 1.8 × 10 −7 mol·J −1 at 2 MGy.…”

Radio-Oxidation Ageing of XLPE Containing Different Additives and Filler: Effect on the Gases Emission and Consumption

“…Whatever the XLPE polyethylene under study, the hydrogen radiation chemical yield decreased when the dose increased. This dose effect has previously been observed under an inert atmosphere [45,46] as well as under an oxidative atmosphere [32] when pure polyethylene was irradiated. The observed decrease has been previously ascribed to the formation of new bonds, also called defects, which act as energy scavengers [45,46].…”

“…This dose effect has previously been observed under an inert atmosphere [45,46] as well as under an oxidative atmosphere [32] when pure polyethylene was irradiated. The observed decrease has been previously ascribed to the formation of new bonds, also called defects, which act as energy scavengers [45,46]. This behavior implies that under homogeneous irradiation conditions, the higher the defect concentrations, the lower the G D (H 2 ).…”