Improved barrier properties for plastics are desirable for a wide range of applications. Barrier materials are used in food and beverage packaging to slow the egress of carbon dioxide or the ingress of oxygen in order to improve quality and extend shelf-life. Traditional barrier materials for plastic articles include metal or silicon oxide coatings and polymers with high barrier properties. High barrier polymers, used either as a coating or as a layer in a multi-layer structure, include some polyamides, EVOH [ethyl vinyl alcohol], or PVDC [polyvinylidene chloride]. Nanocomposites, particularly those based on nanoclays, have been found to significantly improve barrier properties and have some advantages over traditional materials. Nanocomposites have had some commercial successes in barrier applications, with many more in development or approval processes.
Nanoclays are typically based on montmorillonite clay minerals, which have a layered, platey structure that exists as agglomerated bundles of platelets.