Modeling of surfactant release from polymer-clay nanocomposites into ethanol

Abstract

A kinetic study was carried out of the release of surfactants from two types of nanocomposites: polypropylene (PP) and nylon 6 compounded with nanoclay. The migration experiment was performed in accordance with ASTM 4754-11 with the nanocomposite films exposed to ethanol as a fatty-food simulant at 22, 40, and 70 °C. The surfactant release from the nanocomposite films followed a migration behavior as described by Fick's second law of diffusion. Diffusion coefficients derived from the model were in the range of 10−13 to 10−12 cm2 s−1 for the surfactant release from the PP-clay film and 10−13 to 10−11 cm2 s−1 for the surfactant release from the nylon-clay film between 22 and 70 °C. The rate of surfactant release was greater from both nanocomposite films at the higher temperatures. At the same temperature, the rate of surfactant release was greater from the nylon-clay film than from the PP-clay film. Moreover, the surfactant was more likely to be released from the nylon-clay film, as indicated by the smaller partition coefficients (i.e., the ratio of surfactant in the polymer vs in ethanol). The difference in surfactant release between the two nanocomposites was explained by considering the affinity among the surfactant, polymer, and solvent.