Solubility, diffusion, and permeation of gases in gutta‐percha

Abstract

Abstract The permeability of vulcanized gutta‐percha membranes to gases was determined in relation to the rate of diffusion and solubility. The measurements, as functions of temperature, with four gases were taken below and above the melting point of gutta‐percha. The evidence is that the rates of permeation and diffusion increase sharply at approximately 45°C., due to melting of the gutta‐percha. In the same way, although to a lesser degree, the solubility of the gas likewise increases at the melting point. The activation energies of permeation and diffusion with the heat of solution were computed from the temperature function of those quantities. It follows from the results that crystallization of the elastomer reduces the gas‐solubility, the diffusivity, and the permeability—and increases the activation energy of diffusion. The interpretation of this high activation energy of diffusion is that, because of the crystallization, the macromolecules of the membrane adhere so firmly that greater energy is required to admit the gas molecules.