Polyether-block-amide copolymer/clay films prepared via a freeze-drying method

Freeze-drying can be used to prepare polymer/clay aerogels, which offers the opportunity to produce lamellar composites containing very high levels of aligned fillers. A polyether-block-amide copolymer/organoclay aerogel was prepared using t-butanol as solvent and later compression-molded into a film, which exhibited 63.5% lower oxygen permeability compared with the starting polymer, with the addition of 16.7% organoclay by volume. X-ray diffraction revealed that the “aerogel method” provided a way for producing films containing highly exfoliated clay fillers at low clay levels. The aspect ratio for the clay platelets was calculated by fitting the experimental permeation values to classical diffusion models. As the filler ratio was increased, exfoliation was replaced with intercalation and reaggregation, accompanied by an increase in the tensile modulus and a decrease in both tensile strength and elongation at break. The major benefit to use of the aerogel method is the ability to exceed clay levels normally attainable via melt processing.