The melt intercalation method was employed to prepare layered silicate polyamide 6 nanocomposites. Low cost bentonite clay was purified and modified with octadecylamine using different experimental conditions in order to improve efficiency in the modification step. Nanocomposites properties as a function of clay nature, solid content during the modification process and the excess of surfactant in the organophilic clay were analysed. Small Angle X-Ray Diffraction (SAXD) and Transmission Electron Microscopy (TEM) gave a qualitative picture of the microstructure and a correlation to mechanical properties has been established. Thermogravimetric Analysis was used to investigate the surfactant location in the organophilic layer silicates by the identification of the observed thermal degradation transitions. Surfactant excess was found to be one of the crucial parameters to be taken into account. (c) 2005 Elsevier Ltd. All rights reserved.