Benzophenone-sensitized photodegradation of polyethylene

Abstract

The effects of benzophenone (BP) on the photodegradation of polyethylene were investigated by analyzing the ESR and infrared spectra of the irradiated samples. The unsensitized sample irradiated at −196°C with light of λ > 300 nm yielded a spectrum composed of 8-line (alkyl radical) and 5-line (allyl radical) components with splitting constants of 22 gauss and 12 gauss, respectively. With the BP-sensitized sample, the 8-line component decayed, emphasizing the 5-line component. The BP-sensitized samples exposed at room temperature to light of λ > 220 nm and λ > 300 nm exhibited a singlet with a line width of 14 gauss (polyenyl radical) and a 5-line spectrum with a splitting constant of 12 gauss, respectively. Infrared spectra of the irradiated samples showed that BP strongly accelerates the formation of double bonds. It is believed that BP acts in the photodegradation of polyethylene to enhance the formation of allyl and polyenyl radicals, which starts at the double bonds in the sample.