ABSTRACT
The initiation of photo-oxidative degradation of polyethylene requires the presence of species other than those found in the pure material. Saturated carboncarbon and carbon-hydrogen bonds cannot absorb ultraviolet radiation themselves. In order to initiate degradation, chromophores that absorb the appropriate wavelengths of light must be present. Such chromophores include carbonyl groups, unsaturated carbon-carbon bonds, dyes, pigments, catalyst residues, and even antioxidant molecules. Absorption of ultraviolet radiation by chromophores converts them to activated species; as they decay to their ground states, their excess energy can be used to cleave carbon-hydrogen bonds.
