Effect of organoclay purity and degradation on nanocomposite performance, Part 1: Surfactant degradation

The alkylammonium surfactants used to form commercial organoclays are known to begin to degrade at temperatures below the typical melt processing temperatures of some polymers. In this study, the thermal stability and degradation of various surfactants and their corresponding organoclays were investigated. Several factors, such as surfactant type and excess surfactant in the organoclay, that affect the thermal stability of surfactants on organoclays are explored. Nuclear magnetic resonance (NMR) spectroscopy was used to analyze the decomposition products. Thermogravimetric analysis (TGA) was used as the primary method to characterize the thermal stability of these surfactants and organoclays; the neat surfactants lose mass more rapidly, at a given temperature, than the corresponding organoclay. Washing the organoclay with methanol proved to be an effective way to remove the excess surfactant from the clay galleries. Such purification generally improves the thermal stability of the as-received organoclays. Depending on the availability of residual halide anions in the organoclay, the organoclays decompose via either S(N)2 nucleophilic substitution or Hoffmann elimination pathways. (c) 2008 Elsevier Ltd. All rights reserved.