Energy migration effect on the formation mechanism of different unsaturations in ethylene/styrene random copolymers

Abstract

To evaluate the influence of specific parameters, i.e. energy sink concentration and excitons and/or radical migration, on the mechanisms underlying the formation of double bonds in aliphatic polymers, materials with energy sinks in the chain were synthesized. By following the radiation-induced modifications in ethylene/styrene random copolymers, as a function of the styrene content and of the irradiation temperature, we were able to understand the formation mechanisms of trans-vinylenes, trans-trans-dienes, allyl radicals and vinyls. The irradiation temperature allows the discrimination between energy transfers (at 11 K and at room temperature, RT) and of radical migration (at RT). Irradiations were performed using swift heavy ions, and we could show that track overlapping has also an influence on the studied chemical group concentrations. For instance, trans-vinylenes are influenced by excitation transfer and radical migration: their formation decreases in presence of styrene aromatic rings, whatever the dose range and the irradiation temperature. On the opposite, vinyls are formed only at high ionizing density and are not influenced by excitation transfer; however, their concentration is influenced by radical migration.

Radio-Oxidation of Electric Cabled Models: Ageing Evaluation at the Atomic Scale

“…In the case of XLPE M1, all the different oxidised carbon contributions of the material increase with dose and then level off. This evolution has previously been observed and can be attributed to the known tendency towards saturation commonly observed in non-protected polymers irradiated at high doses and attributed to an equilibrium between bonds destroyed and created upon further irradiation [41][42][43]. A similar kind of evolution is evidenced for XLPE M3(IrgPS802); this polymer contains the secondary antioxidant alone, and it can be assumed that Irganox PS802 is not efficient when inserted in the material without any primary antioxidant.…”

Effect of oxygen on gas emitted from polymer irradiated using Swift Heavy Ion beams

“…In fact, PUR polymers present ester groups in their soft segments and aromatic rings in their hard segments; PS presents aromatic rings as pendant groups. These two kinds of groups are very well known to be effective energy scavengers [1,3,34,35] and they will lower the radiation induced polymers degradation. Nevertheless, their protective efficiency decreases when stopping power increases [3]: the formation yield of radicals will thus increase with LET, leading at equivalent stopping power to a more important concentration of radicals, themselves reacting with oxygen.…”