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Effect of sub‐T g relaxations on the gas transport properties of polyesters
Author(s) -
Light R. R.,
Seymour R. W.
Publication year - 1982
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760221402
Subject(s) - polyester , activation energy , materials science , relaxation (psychology) , diffusion , ethylene , amorphous solid , arrhenius equation , solubility , polymer , glass transition , permeability (electromagnetism) , polymer chemistry , poly ethylene , chemistry , thermodynamics , organic chemistry , composite material , catalysis , psychology , social psychology , biochemistry , physics , membrane
The relationship was determined between sub‐ T g molecular motions and the transport of O 2 and CO 2 in amorphous polyesters and copolyesters based on poly(ethylene terephthalate) [PET] and poly(1,4‐cyclohexylenedimethylene terephthalate) [PCDT], Modifications of the polyester with certain acid co‐monomers restricted the molecular motions that occurred in the β‐relaxation region and in turn decreased the O 2 diffusion coefficient. The solubility coefficient was unchanged by those modifications. Modification of PET with 1,4‐cyclohex‐anedimethanol increased the magnitude of the β‐relaxation and both the diffusion and solubility coefficients of O 2 . Similar relationships between the β‐relaxation magnitude and CO 2 permeability were also found. The temperature dependence of O 2 permeability followed an Arrhenius relationship, with different activation energies ( E p ) above and below the β‐relaxation. The activation energy was smaller below the β‐relaxation. Values of E p above and below the β‐relaxation did not depend on the chemical structure of the polymer.