Sensitization of the radiation-induced chain oxidation of aromatic amines in polymer films (038)

Abstract

The sensitization of the chain redox reaction in γ-irradiated solid films of poly(vinyl chloride) (PVC), containing N, N, N ′, N ′-tetramethyl-4,4 ′-diaminodiphenylmethane (Am), CBr 4 and naphthalene, was investigated by the electron spin resonance and optical spectroscopy methods. The ESR spectra of the γ-irradiated PVC films at 77 K with the additives of Am, CBr 4 and naphthalene were studied. The effects of radiation dose and annealing temperature on the transformation radicals were investigated. The spectra of radicals, taking part in the chain reaction, were separated and identified. The radiation-chemical yields of these radicals and their thermal stability were determined. The dependencies of radical concentration on the annealing temperature for samples in the presence and in absence of naphthalene were compared. It was established that the addition of naphthalene up to 0.2 kmol/m 3 results in an increase of the chain reaction yield from 80 to 150 particle/100 eV in the case if the samples are irradiated at 300 K. If the irradiation is made at 77 K, the yield of oxidized amine Am + after annealing at 293 K rises from 20 to 45 particle/100 eV as a result of action of naphthalene. The analysis of ESR spectra, made by a computer subtraction, showed that the radiation-chemical yield of free radicals Am , initiating the chain reaction, is not changed in consequence of the addition of naphthalene. Therefore we suggest that the sensitizing activity of naphthalene is caused by increasing the polymer chain flexibility and, consequently, the diffusion coefficient of active CBr 3 radicals, the chain propagating species.