Preparation and properties of epoxy nanocomposites. I. The effect of premixing on dispersion of organoclay

The objective of this work was to systematically study the effect of the conditions of shear and temperature used to premix nanoclay with epoxy resin on the dispersion and intercalation/exfoliation of the nanoclay in the resulting epoxy nanocomposites. The different mixing approaches used were hand stirring, conventional mechanical stirring, a high-speed homogenizer, and a microfluidizer. The quality of dispersion and intercalation/exfoliation of the organoclay in the epoxy resin was analyzed after premixing (before adding hardener) by means of X-ray diffraction (XRD) and rheological measurements. Nanocomposites obtained after adding hardener and curing were characterized by means of XRD, field emission gun scanning electron microscopy, transmission electron microscopy, and image analysis. Both the premixing and curing steps were found to play a determining role in the dispersion and intercalation/exfoliation of organoclay. Increased intercalation and exfoliation can take place during curing, with the extent depending on the curing rate. Although full exfoliation of clay cannot be achieved at the premixing stage, this step appears to be very important in controlling the micro-dispersion and thus affecting the further intercalation and exfoliation that take place during the curing step.