Abstract

Although broadly defined as a macromolecule having the ability to restrict the passage of gases, vapors, and liquids, the functional definition of a barrier polymer varies from application to application and a material that provides sufficient barrier for a particular end use can be considered to be a barrier polymer. They are widely used in food, beverage, and other packaging industries. Some of the advantages that they offer over traditional packaging materials such as glass, paper, and metals are flexibility, light weight, toughness, versatility, and printability. However, unlike glass and metals, no polymer offers an infinite gas barrier. Combinations of different polymers, or polymers with inorganic materials, in the form of multilayer structures or blends, can provide sufficient barrier for the intended shelf life of most products. Inorganic materials such as silicon and aluminum oxides and nanoclays can significantly enhance barrier and other mechanical properties of polymers. Other approaches for improving barrier properties such as oxygen-scavenging systems have also received considerable attention in recent years. This article discusses various types of barrier polymers and structures, their permeability characteristics (including the underlying principles involved), measurement techniques, ways to predict and improve barrier properties, and current as well as potential future applications for barrier polymers.