Study on the effect of 7-hydroxycoumarin on photo-oxidative degradation of LLDPE films

Photo-oxidative degradation of LLDPE films (~ 250 μm thick) containing varying amounts of 7-hydroxycoumarin (HC) (a type of coumarin derivative) was investigated by exposing the films to an artificial sunlight (emitted by 300 W OSRAM Ultra-Vitalux lamps) at 40○C for extended time periods. Photo-oxidative degradation of the neat polymer film and the LLDPE films containing coumarin alone were also studied under similar conditions for comparison. The rate of photo-oxidation was assessed by measuring tensile properties, gel content, carbonyl index, molecular weight and density. It was shown that HC has a moderate stabilization effect in photo-oxidation of LLDPE films. However, the film containing coumarin did not exhibit different behaviour in photo-oxidation relative to the neat LLDPE film during the exposure time. On the basis of the obtained results, the photo-oxidative stabilizing activity of HC was described in terms of the activity of phenolic hydrogen present in the substituted moieties of HC molecules

کلیدواژه ها:

polyethylene ، 7-hydroxycoumarin ، photo-oxidative stability