Clay/Polymer nanocomposites: Processing, properties, and applications

Clay/polymer nanocomposites have been extensively studied in recent years. The present state of the art for these materials is summarized in this chapter. The development of fabrication methods for these composites is very challenging because the platelets of nanoclay exist in the form of clusters, which need to be dispersed in the matrix resin in order to obtain any benefit from the high surface area of nanoclay. Incorporation of only a small weight fraction (1-5 %) of nanoclay in polymers provides significant benefits in the properties of composites. Several tensile, flexural, and thermal properties are found to increase by 30-40 % due to the presence of nanoclay in the composite compared to the properties of the neat resin. Entrapment of air porosity at higher nanoclay content can lead to reversal of the trends and can actually reduce the mechanical properties of nanocomposites. Theoretical models have been developed to estimate the properties of nanocomposites by accounting for the microstructure that may include clustered, intercalated, or exfoliated nanoclay. The benefit in mechanical properties obtained from incorporating nanoclay is much greater than that can be achieved with microscale reinforcement at the same loading levels. The current applications of clay/epoxy nanocomposites are in the area of automotive moldings and fire retardant coatings.