Nano-voids in epoxy resins: Role in the transport of light gases

Publication date: 24 March 2017
Source:Polymer, Volume 113
Author(s): David Roilo, Pushkar N. Patil, Roberto S. Brusa, Antonio Miotello, Riccardo Checchetto
Epoxy membranes with same chemical structure but different free volumes were prepared using aliphatic epoxide and polyether diamines as cross-linking agents. Their fractional free volume fh(T) was previously evaluated as a function of temperature and cross-linking density [P. N. Patil et al., PhysChemChemPhys18 (2016) 3817–3824]. Original H2 permeation measurements were performed changing sample temperature and network structure and compared with CO2 and N2 transport data. Modelling gas permeability Φ in the framework of the free volume theory we observe that the Arrhenius-type behavior of Φ for test gases is consequence of the fh(T) linear increase with temperature and that at equal fh value membranes exhibit increasing Φ values by decreasing the cross-linking density. Analysis of permeability data on this set of test molecules with different size and condensation properties suggests that increasing the cross-linking between polymer chains limits their thermal fluctuations and the redistribution of the free volume elements where diffusional jumps of penetrant molecules occur.

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