XPS Studies on the Surface Oxidation of Photo Crosslinked Polyethylene

The surface oxidation of photo crosslinked polyethylene (XLPE) was studied by X-ray photoelectron spectroscopy (XPS).The XPS analyses show that during the photo crosslinking,the polyethylene surface has been oxidized when it was UV-irradiated in the melt in nitrogen,and the oxidation of XLPE becomes more serious when the UV-irradiation time is longer.In the other hand,oven aging can also cause oxidizing of XLPE.After the XLPE samples were aged at 135℃ for 168h in the oven,the main oxidation products are -CH₂O-,C=O and hyperoxide for the samples UV-irradiated for shorter time,however the contents of oxidation products -COOR and -COOH increase obviously for the samples UV-irradiated for longer time.In addition,efficient antioxidants for XLPE and their antioxidation mechanisms were also investigated.The resluts show that phenol and phosphite ester have good synergism and their combination can significantly improve the antioxidant rpoperty of XLPE materials.