Characterisation of nanoclay dispersion in resin transfer moulded glass/nanoclay/epoxy composites

A novel approach for characterisation of nanoclay dispersion in polymeric composites using electron microprobe analysis (EMPA) is presented. Dispersion analysis was performed on three sets of centre-gated discs fabricated by resin transfer moulding. The first set was neat epoxy polymer without reinforcement, whereas the second set comprised 17 vol.-% randomly oriented chopped glass fibre preforms. The last set, in addition to the glass fibre reinforcement, contained 1·7 wt-% Cloisite 25A nanoclay. Upon completion of curing, a sample along the radius of a nanoclay reinforced disc was analysed on a Cameca SX50 electron microprobe analyser. The results from scanning electron micrographs indicated that nanoclay exists in clusters of various sizes ranging from over 10 μm down to submicrometre scale. Nanoclay clusters larger than 1·5 μm, were analysed by digital image processing on the scanning electron micrographs taken along the part's radius. The dispersion of nanoclay smaller than 1·5 μm was quantified by compositional analysis via wavelength dispersive spectrometry (WDS). Distribution of nanoclay clusters larger than 1·5 μm was found to be approximately constant along the radius with an average value of 1·4% by volume. Similarly, nanoclay clusters smaller than 1·5 μm were found to be distributed evenly with an average value of 0·41 wt-%. To investigate the effect of nanoclay on thermo-mechanical properties, glass transition temperature of moulded samples was measured under oscillatory shear. At the current dispersion state, the glass transition temperature improved 11% with the addition of nanoclay.