Characterization of degradation on gamma-irradiated recycled polyethylene blends by scanning electron microscopy

The recycling of polymer blends has gained increasing attention in the world due to economic and environmental considerations. The exposure of recycled polyethylene blends to low doses of Co-60 gamma radiation improves their mechanical properties due to crosslinking. It is agreed that gamma irradiation in air may cause degradation with oxidation occurring near the surfaces. Usually degradation means worsened properties. Then, it is important to estimate the extent of oxidation depth under those conditions. Samples of recycled polyethylene blends after exposure to gamma rays were examined by scanning electron microscopy (SEM). Permanganic reagent, developed for revealing semicrystalline morphologies in polyolefins under the electron microscope, has been used to monitor the superficial degradation. A detailed characterization of the material behavior has been made by mechanical and physico-chemical testing. The data presented in this article for recycled polyethylene blend after exposure to gamma rays in the air provide evidence of that the increase of radiation dose promotes a higher surface degradation. The effect of gamma radiation is clearly seen in the specimens irradiated with different doses and may be related to the changes in the mechanical properties. (C) 2001 Elsevier Science Ltd. All rights reserved.