The charge decay kinetics in irradiated rubber after exposure to light

Abstract

The kinetics of the decay of charged particles trapped in a butadiene-acrylonitrile (BDAN) copolymer, with or without electron donor or acceptor additives, and irradiated at 77°K, were studied. The kinetics of charge decay on exposure to light of decreasing wavelength are “stepwise” in nature. The charge recombinations produced by light of λ ⩾ 700 nm in rubber with or without addition of phenyl-β-naphthylamine proceed in two stages (a rapid and a slow one), while there is only a single stage in rubbers with addition of chloranil. The charge recombination kinetics can be formally described by a reaction of first order in both the stages. The rate constant of the charge decay drops in the presence of an electron donor or acceptor, and on increasing the γ-radiation dose. The formation of radicals competes with that of molecular products during the photo-recombination of the charges. The efficiency of charge elimination depends on the visible light intensity, i.e. raising the latter will result in an additional decrease in the concentration of paramagnetic centres.