Change of mechanical properties of LDPE during its radiochemical aging

Tensile samples of LDPE were irradiated in air and in nitrogen at various dose rates. By carbonyl FTIR titration on microtome sections, it was established that the depth of the oxidized layer is a decreasing function of the dose rate. The analysis of the change of tensile properties is complicated owing to the fact that chain scission and crosslinking (having the opposite effect on ultimate tensile properties) predominate respectively in the superficial and in the core zone. A sharp decrease of the ultimate elongation seems to occur when the depth of the oxidized layer becomes higher than 170-180 μm. This behavior, which was already observed in the case of HDPE, could be explained in terms of fracture mechanics