Modification of Free Volume due to Rigidness of Polymeric Matrix and Effects on Gas Transport Properties

Abstract

Gas barrier properties of polymeric membranes with different rigidness of their matrix where studied by gas phase permeation measurements. Gas transport results in membranes made of epoxy resin with different cross linking densities and epoxy resin with dispersed few layer graphene fillers were discussed and compared in the framework of the free volume theory of diffusion. Transport in cellulose membranes was found to occur in the diffusion configurational regime. The physical description of the transport properties was based on positron annihilation lifetime spectroscopy measurements which allowed to evaluate experimentally the fractional free volume in epoxy resin membranes and the size of rigid elongated cavities in cellulose thin films.

Open Volumes Structure and Molecular Transport in Biopolymer Nanocomposites

“…Details about permeation measurements can be found in Refs. [12] and [13]. In brief, test gases with different molecular size kept at constant pressure fill a chamber (high pressure side).…”

“…The gas transport through the polymeric membranes is controlled by the solution-diffusion mechanism. The analysis of the permeation curves with the Fick diffusion equation with assumption that Henry's law controls gas absorption in the membranes layers [12][13][14], permit to evaluate the gas diffusivity D and the permeability P = DΠ where Π is the gas solubility in the membrane layers. Measurements as a function of the temperature of the membrane, allow to construct the Arrhenius plot for diffusivity, permeability, and solubility, from which the activation energies of the three processes can be obtained.…”