Microstructure and exfoliation mechanism of clay particles of epoxy/clay nanocomposites under external shearing force

Different processing methods such as magnetical stirring, high-speed emulsifying and homogenizing and ball milling, were used to homogenously disperse the clay agglomerates and facilitate their exfoliation in epoxy/clay nanocomposites. The mechanical properties and effect of external shearing force on the exfoliation of organic clay modified with organic amine, quaternary ammonium salts and the combination of quaternary ammonium salts and meta-xylylenediamine (MXDA) were investigated. It was found that, for the general stirring, only partially exfoliated structure for the small clay particles or the external layers of large clay agglomerates were obtained. While the fine exfoliation for the external and central layers can be easily achieved by exerting vigorous shearing force, and the catalytic role of acid primary alkylammonium is not the key influencing the exfoliation of clay in epoxy matrix. The impact strength and flexural strength of epoxy/clay nanocomposites can be dramatically improved, which was about 50% and 8% higher than those of the pristine epoxy, respectively. The degree of exfoliation of clay particles will be substantially determined by the pulverization of the clay agglomerates. The smaller the size of clay particles, the better the dispersion and exfoliation of clay layers are, and a simultaneous outward shift of the external and central layers occurs.