Effect of sub‐T_g relaxations on the gas transport properties of polyesters

Abstract

The relationship was determined between sub‐Tg molecular motions and the transport of O2 and CO2 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 O2 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 O2. Similar relationships between the β‐relaxation magnitude and CO2 permeability were also found. The temperature dependence of O2 permeability followed an Arrhenius relationship, with different activation energies (Ep) above and below the β‐relaxation. The activation energy was smaller below the β‐relaxation. Values of Ep above and below the β‐relaxation did not depend on the chemical structure of the polymer.

Synthesis, physical characterization, and acetone sorption kinetics in random copolymers of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate)

“…Light and Seymour reported oxygen and carbon dioxide permeability in various polyesters including PET, PEN, and a 50/50 copolymer of PET and PEN. 6 These results are presented in Table I. At 30°C, CO 2 and O 2 permeability coefficients were lower in PEN than in PET, and the gas permeability of a 50/50 PEN/ PET copolymer was between that of homopolymers.…”

Antiplasticization of a polyamide: a positron annihilation lifetime spectroscopy study

“…Because of that, there are changes in physical properties of the polymeric materials. For instance, modulus and strength increase whereas ductility and permeability to gases decrease [3 -13], there is a suppression of sub-T g relaxation processes [14], etc.…”

Synergism and multiple mechanical relaxations observed in ternary systems based on benzoxazine, epoxy, and phenolic resins

“…A relationship between the secondary relaxation temperature and transport properties of polymers has also been reported. 10,11 A systematic investigation of the relaxation spectra can ultimately lead to the prediction of the structure or architecture of the materials and, thus, the corresponding properties of the materials. 9 Furthermore, DMA has been proven to be a much more accurate tool for the indication of the transition points in materials, particularly for secondary transitions in comparison with other methods such as differential scanning calorimetry (DSC) and thermomechanical analysis (TMA).…”