Hysteresis in the relation between moisture uptake and electrical conductivity in neat epoxy
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AbstractMonitoring changes in electrical conductivity is a simple way to assess the water uptake from environmental moisture in polymers. However, the relation between water uptake and changes in conductivity is not fully understood. We monitored changes in the electrical volume conductivity of an anhydride-cured epoxy polymer during moisture sorption-desorption experiments. Gravimetric analysis showed that the polymer exhibits a two-stage sorption behavior resulting from the competition between diffusive and reactive mechanisms. As expected, the macroscopic electrical conductivity increases with the diffusion of water. However, our most surprising observation was severe hysteresis in the relation between water uptake and electrical conductivity during the sorption and desorption experiments. This indicates that change in the electrical conductivity depends on both the water uptake and the competition between the diffusive and reactive mechanisms. We studied samples with various thicknesses to determine the relative effects of the diffusive and reactive mechanisms. This is an important observation as it means that general electrical monitoring techniques should be used cautiously when it comes to measuring the moisture content of polymer or polymer-based composite samples.
CitationLubineau G, Sulaimani A, El Yagoubi J, Mulle M, Verdu J (2017) Hysteresis in the relation between moisture uptake and electrical conductivity in neat epoxy. Polymer Degradation and Stability. Available: http://dx.doi.org/10.1016/j.polymdegradstab.2017.05.008.
SponsorsThe research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). We thank KAUST for its continuous support.