The Importance of Hydroxyl Radicals as Intermediates in the Cross-linking of High Polymers by γ-Irradiation

TLDR: In this article, the authors have irradiated thin gelatin films (thickness 0.5-1.0 mm) with cobalt-60 γ-rays at a dose-rate of 4.2 × 104 r.

Abstract: WE have irradiated thin gelatin films (thickness 0.5–1.0 mm.) with cobalt-60 γ-rays at a dose-rate of 4.2 × 104 r. hr.−1 at 10° C. The film was either suspended in a stoppered bottle containing oxygen or nitrogen or immersed in a liquid which filled the bottle. After irradiation of the film, attempts were made to dissolve it in 19 times its own weight of water at 40° C., and the viscosity of any resultant solution was measured. No increase in relative viscosity was observed when the irradiation was carried out in an atmosphere of oxygen or nitrogen, or when the film was suspended in liquid paraffin, benzene, ether, cyclohexanone, pyridine, acetone or an alcohol, even when the dose exceeded 1 mega-roentgen. In the presence of water, however, the gelatin became cross-linked, as was shown by the fact that it was merely swollen by treatment with boiling water.