To explore the possibility of making poly(p-phenylene sulfide) (PPS) nanocomposites via melt intercalation and improving the mechanical properties of PPS, in this study we first modified clay (montmorillonite) with alkylammonium salt by cation exchange and then mixed the modified clay together with the PPS matrix by twin-screw extrusion. Because the PPS/clay composites were made at a high temperature (300 degrees C), thermogravimetric analysis experiments were carried out first to check the thermal stability of the alkylammonium salt treated clay and the obtained composites. Possible degradation of the alkylammonium salt during processing caused a decrease in the interlayer spacing of the clay. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction were used to investigate the dispersion of the clay sheet in the matrix. The clay layers were homogeneously dispersed in the PPS matrix with a nanometer scale, and an exfoliated structure was achieved at a low load of clay. The alkylammonium salt modifier enhanced the interaction between the PPS and clay on the one hand, but on the other hand, it also acted as a plasticizer and caused decreases in the glass-transition temperature and tensile properties. More work is needed to find a modifier and processing conditions by which the modifier can help the dispersion of clay and also be completely degraded after the formation of an exfoliated structure.(c) 2005 Wiley Periodicals, Inc.