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

Abstract

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.

Modeling the delamination process during shear premixing of nanoclay/thermoset polymer nanocomposites

“…For more information on the dispersion of clay and the effect of premixing parameters, refer to Refs. 6 and 7.…”

“…By increasing the viscosity of the epoxy‐clay suspension, the speed required for delamination of clay can reduce. In addition, premixing temperature and time also need to be considered, since they has a slightly influence on the d ‐spacing, 6, 7 and hence on the interlamellar spacing h. This also may help to reduce the velocity needed to separate the clay platelets.…”

“…Several studies on the effect of shear force on dispersion and properties of thermoplastic nanocomposites have been reported in the literature based on shearing devices such as extruders, mixers, and ultrasonicators. 1–7 However, the mixing devices used for uncured thermoset systems are different from these devices and the rheological properties of uncured thermoset resins are very different from those of thermoplastic polymers. Therefore, the effect of shear flow on the dispersion of nanoclays in thermoset polymers has not been studied in detail, especially at the premixing stage where the clay and epoxy are combined before curing.…”

Preparation and properties of epoxy nanocomposites. Part 2: The effect of dispersion and intercalation/exfoliation of organoclay on mechanical properties

“…Epoxy and clay were pre‐mixed together by means of different devices as reported in our previous study [9]. Samples specifications are shown in Table 1.…”

“…Achieving such well‐intercalated/exfoliated morphologies with epoxy‐based nanocomposites is a challenge, since high shear is always required but epoxy resin typically has rather low viscosity. From the results of our previous study, well‐dispersed and well‐intercalated/exfoliated ENCs were obtained with a nonsolvent‐assistance method [9]. In this study, the exploration of a different way to generate the shear in order to improve the quality of dispersion and intercalation/exfoliation of clay in epoxy was studied.…”