A Permeability Model for Polymer-Clay Nanocomposites with Varying Clay Platelets Thickness

Abstract

Polymer-clay nanocomposites (PCNC), are characterized by the high ratio of surface area to volume of the clay nanoparticles which are in the form of clay platelets with very high aspect ratio. This feature provides superior gas barrier properties at very low volume fraction of the nanofiller. Clay platelets introduce discontinuity to flows through the bulk polymer matrix material. The extent of this improvement depends on the success of separation of clay layers during processing which would produce single-layer particles (exfoliation) or several-layer particles (intercalation) through the bulk polymer matrix. This paper discusses the common permeability models used to capture the effects of the clay nanofillers in PCNC. Since these models assume a state of full exfoliation of clay platelets; that is a single phase of the nanofiller, they fall short of representing the actual state as evidenced by experimental works, which confirm the presence of both the intercalated phase and the exfoliated phase. A model that incorporates clay inclusions with different sizes (different thicknesses) is proposed and its implications are assessed.