Abstract
The effect of N,N‐dialkyl dithiocarbamate substitution on the radiation stability of poly(vinyl chloride) (PVC) film was studied. PVC containing 6.5–15.7 mole‐% N,N‐dimethyl dithiocarbamate (PDM) and PVC containing 8.3–17.5 mole‐% N,N‐diethyl dithiocarbamate (PDE) was irradiated with γ‐rays from a Co‐60 source at room temperature under vacuum. The evolved gaseous products were measured and analyzed with a mass spectrometer. The apparent G values for gas evolution of PDM and PDE decreased remarkably. For example, a G value of 0.10 was obtained for a PDE which contains 17.5 mole‐% diethyl dithiocarbamate group. The mass spectrum of the evolved gas from the same PDE sample with 10‐Mrad irradiation showed no hydrogen chloride to be present. The external protection was studied using polymer‐blended films of PVC and PDE or PDM. The stabilization coefficients for internal protection and external protection in polymer blends were calculated. Although the ESR spectrum of the irradiated PDM, PDE, and PVDE which is synthesized by polymerization of S‐vinyl‐N,N‐diethyl dithiocarbamate (VDE) showed the same sulfur radicals, they were different from those of the irradiated cysteamine hydrochloride and PVC containing N‐methyl dithiocarbamate (PMD). From these results, the protection of a polymer by a covalently bound dithiocarbamate was discussed.