Free radicals trapped in polyethylene matrix

The kinetics of the decay of main chain free radicals trapped in polymer matrix in vacuum were investigated. The decay behaviour of alkyl radicals trapped in the lamellar surface of the crystallites of solution grown polyethylene should be different from that of the same radicals trapped in the inner part of the crystallite, and this difference was clearly observed. The analysis of the data of the decay reaction was made, based on three-dimensional diffusion-controlled reaction theory, and reasonable interpretation of the data was made. Alkyl radicals were also observed in an irradiated urea-polyethylene complex and the decay rate of these radicals was very slow in spite of the large mobility. It was concluded that the mechanism of three-dimensional diffusion of the free radicals across the chain may occur in the inner part of the crystallites via hydrogen abstraction reactions. (author)