Physical properties of polymer/clay nanocomposites

Interest in polymer/clay nanocomposites began in 1989 with the publication of a paper by the Toyota Central Research group detailing very unusual physical property improvements in a nylon 6/clay nanocomposite. This sparked a very large worldwide effort of research on these type of composites. This paper looks at the state of knowledge about polymer/clay nanocomposites and the general trends seen in selected physical properties and the theoretical basis if know for the observed changes. The paper is not meant to be an exhaustive review of the thousands of papers currently published on the subject. Particular emphasis is given to the ability of modified Halpin–Tsai and Mori–Tanaka re-enforcement theories to predict the modulus of a true exfoliated nanocomposite. Data indicates that the level of exfoliation in these composites is one of the critical parameters in determining changes in properties. In addition to physical properties such as modulus and impact strength other phenomena such as improved flame retardancy and gas barrier properties are discussed.