Properties of paraffin wax/montmorillonite nanocomposite coatings

Results are reviewed from a study aimed at enhancing the performance of paraffin wax based materials for barrier coating applications. Nanocomposites prepared by ultrasonic processing from paraffin wax matrices and reinforced with organically modified montmorillonite clay have been shown to demonstrate significantly improved mechanical properties. This includes substantially increased stiffness, strength and ductility relative to pure paraffin wax. Subsequent to processing, the clays were found to be well-dispersed as exfoliated and intercalated platelets of about 50-150 nm in length and a few nanometers in thickness. Dilatometry results presented here show that the relative volume expansivity of the organo-clay reinforced nanocomposites are significantly decreased compared with that of the pure wax. The corresponding topology study shows that the formation of micron-size cracks on the wax surface during cooling is inhibited by the clay. It is also shown that the presence of organo-clay appears to stabilize the properties of melt processed samples. For example, the contact angle for water on solid paraffin wax surfaces decreases with increased periods of heating time for molten samples. The extent of the observed changes is significantly less in the nanocomposites. Our study demonstrates that there are a number of benefits associated with the addition of organo-clay to paraffin wax barrier coatings. In addition to enhanced strength, durability and aesthetics, the presence of the nano-disperse particles also appears to maintain or improve properties that decay with processing.