Photo-oxidative degradation of LLDPE films (~ 250 μm thick) containing varying amounts of galbanic acid (a type of coumarin derivatives) 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 benzophenone (an active photo-initiator for PE) and 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 galbanic acid was highly effective in accelerating photo-oxidation of LLDPE films and an outstanding acceleration of photo-oxidation was observed for the film containing 0.2 wt % of galbanic acid in comparison with the film containing the same amount of benzophenone. However, the film containing coumarin did not exhibit considerable difference in behaviour in photo-oxidation relative to the neat LLDPE film during the exposure time. On the basis of the obtained results, the prooxidant activity of galbanic acid was described in terms of activity of the functional groups existing in the substituted moiety of its molecules.
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