Copolyaramide As a Barrier Material

Abstract

The films of heterocyclic copolyaramide used at NPO OOO “LIRSOT” for the production of high-strength polyaramide threads are obtained, their gas transport characteristics for helium, oxygen, and carbon dioxide are studied, and the parameters of free volume elements are investigated by positron annihilation lifetime spectroscopy. According to the data obtained, the copolyaramide under study belongs to the class of polymers with high barrier characteristics and its properties are close to those of the commercial samples of thermotropic liquid-crystalline copolyesters Vectra. The low values of gas permeability of copolyaramide are related to decreased gas diffusion coefficients. A comparison of the activation energies of permeability, diffusion, and sorption enthalpy of gases shows that these parameters are also comparable to those of barrier polymers. The gas permeability data are confirmed by positron annihilation lifetime spectroscopy: the sizes of free volume elements obtained for copolyaramide (R₃ = 2.5 Å) are also comparable with those for copolyester Vectra (R₃ = 2.1 Å). The results of this study demonstrate that the tested domestic heterocyclic copolyaramide can be used for the manufacture of barrier films and coatings as a substitute for Vectra liquid-crystalline copolyesters.