Diffusion and Permeation of Hydrogen Isotopes in/through Polycarbonate Ⅱ

Permeation and solution of tritium through/in organic polymers are important problems for applying these materials to tritium handling systems. In this connection, the solution and diffusion of tritium in several polymers were studied by means of time-lag method and considerable abnormal behavior for tritium permeation though polycarbonate film was observed. The causes of this abnormality were investigated by measuring diffusivity and solubility of tritium under various experimental conditions. It was observed that the solubility and diffusivity and hence permeability of tritium was significantly affected by the presence of residual solvent originating from the manufacturing processes. In addition, the residual solvent enhanced the solution of isobutene contained in counting gas when the permeation was measured by β-ray counting method using G-M counter. Both the residual solvent and dissolved isobutene disturbed the diffusion of tritium. The latter, however, significantly impaired the diffusion of tritium. When the residual solvent was removed from the film in vacuum and the permeation was measured by quadrupole mass spectrometer, the abnormality disappeared and normal isotope effect was observed. The extent of isotope effect, however, differed from that of the classical rate law prediction