Moisture absorption and spectroscopic studies of epoxy clay nanocomposite

Abstract

AbstractEpoxy resins are prone to serious moisture absorption inspite of their inherent advantages, which can be mitigated by the incorporation of montmorillonite nanoclay that provide tortuous path to flow of moisture. Moisture absorption studies of epoxy clay nanocomposites is carried out, to analyse the effect of nanoclay content, immersion media and immersion temperature. Nanocomposites prepared in 0.5, 1 and 1.5 wt% using magnetic stirring and ultrasonication and neat epoxy specimen were immersed in distilled water and artificial seawater maintained at 28 and 38 °C till saturation. Fick’s and Langmuir’s models were applied to calculate the kinetic parameters from the water absorption graphs. Atomic force microscopy (AFM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope with energy dispersive X-ray (SEM–EDX) characterizations were performed. Diffusivity is least for nanocomposite containing 0.5 wt% nanoclay at both temperatures in both medium. However, it is least when the medium is distilled water. As the temperature of immersion medium increases, the diffusivity also increases. Saturation moisture uptake increased with increase in nanoclay content, because of the residual hydrophilic nature of nanoclay. AFM and XRD analysis revealed better dispersion and exfoliated structure of nanoclay respectively at 0.5 wt% loading. FTIR spectroscopy was applied to identify the chemical bonds that helped in proposing the reaction mechanism of the nanocomposite synthesis. Spectra comparison of dry and wet specimens complimented the moisture absorption data by showing lower infrared transmittance in wet specimens. With Increase in nanoclay content, the transmittance decreased corresponding to increase in saturation moisture uptake for distilled water immersed specimens. SEM–EDX analysis distinguished between the cations entered from the artificial seawater and cations that were still present in the nanoclay.