Surface photo-oxidation and photostabilization in photoinitiated crosslinking of polyethylene

The surface photo-oxidation and photostabilization in the photoinitiated cr osslinking of polyethylene were studied using Fourier transform infrared sp ectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and the determin ation of gel content with irradiation time. The data show that the surface photo-oxidation of photocrosslinked polyethylene (XLPE) increases apparentl y with increasing UV-irradiation time. The main photo-oxidation products ha ve been identified as hydroperoxides and various carbonyl compounds. The ph otostabilization of XLPE can be realized by suitable pre-irradiation using low-pressure mercury(LPM) lamp or by the addition of some hindered amine li ght stabilizers (HALS). The optimum time of pre-irradiation by LPM lamp is 10 s under the experimental conditions in the present study. However, some HALS can reduce the efficiency of photoinitiated crosslinking process of PE .