Crystallization Behavior of PA-6 Clay Nanocomposite Hybrid Eric Devaux, Serge Bourbigot, Ahmida El Achari Laboratoire de Ge ´nie et Mate ´riaux Textiles (GEMTEX), UPRES EA2461, Ecole Nationale Supe ´rieure des Arts et Industries Textiles (ENSAIT), BP 30329, 59056 Roubaix Cedex 01, France Received 25 September 2001; accepted 27 December 2001 Published online 19 September 2002 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/app.10920 ABSTRACT: Polyamide-6 (PA-6)/clay (modified mont- morillonite) hybrid was synthesized by melt blending at high shear stress. 27 Al-NMR of solid state shows that the clay is not modified after melt blending. Using wide-line 1 H-NMR and TEM, it is demonstrated that the nanocom- posite exhibits mainly an exfoliated structure. It is shown that the modified montmorillonite induces the crystalliza- tion of PA-6 predominantly in -form. The presence of clay in PA-6 increases the polymer crystallization temper- ature, and decreases its melting point. These phenomena show that a certain number of interactions develop near the reinforcing material, and that the latter plays a par- ticular role of nucleating agent. However, the crystalliza- tion is not spherulitic and the assumption of macromolec- ular orientation in the vicinity of the clay is demonstrated by the observations carried out in DSC and AFM. These particular properties of orientation will have a particular importance on the mechanical behavior of the nanocom- posite material. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2416 –2423, 2002 Key words: nanocomposites; polyamides; crystallization INTRODUCTION Polyamide resins are widely used as injected and ex- truding molded materials and in the textile industry. They have been successfully reinforced using glass fibers and other inorganic additives. 1 Nevertheless, in such composites, the polymer and the additives are not homogeneously dispersed. To overcome this prob- lem and to improve the properties of the host poly- mer, molecular composite of thermoplastics was syn- thesized. The studies on nanocomposites began in the early 1980s at Toyota Central Research Laboratories. 2 The first licensee of Toyota’s nanocomposite technol- ogy was Ube Industries, which developed a poly- amide clay nanocomposite. Other polymers have been tested as matrices: 3 epoxy, 4–6 polyether, 7 and poly- (ethylene oxide). 8 Polymer clay hybrids offer superior properties (high strength, high modulus, and high heat resistance 9,10 ) in comparison with the original polymer. Recently, it was reported that polymer-lay- ered silicate (clay) have the unique combination of reducing flammability and of increasing heat resis- tance at very low loading (2–5 wt %). 11–13 In this article, the polyamide-6 layered-silicate pre- pared by melt-extrusion process is characterized in a first part, by solid-state NMR of 27 Al, 13 C, and wide- line 1 H, X-ray diffraction and TEM to determine the nanocomposite structure. In a second part, the crys- tallization behavior of the nanocomposite material is discussed. It is studied by differential scanning calo- rimetry (DSC) and by atomic force microscopy (AFM). The aim of this work is to clarify what is the precise role of the clay on the crystallization of PA-6. EXPERIMENTAL Materials Raw materials used for the preparation of poly- amide-6 clay hybrid (PA-6 nano) were sodium mont- morillonite modified by methyl, tallow, bis-2-hy- droxyethyl, quaternary ammonium chloride supplied by Southern Clay Product (Cloisite 30B) and poly- amide-6 (PA-6) as pellets supplied by Rhodia (Technyl C206). Clay and PA-6 were dried 48h at 80°C before extrusion. Preparation of polyamide-6 clay hybrid Polymer melt-direct intercalation is an approach to make polymer layered silicate nanocomposites by us- ing a conventional polymer extrusion process. PA-6 was melt mixed with the clay using a counterrotating twin-screw extruder (Brabender) according to condi- tions that permit the formation of nano-structured material. 14 The rotational speed was 300 rpm to have high shear stress, and the temperature of the five heating zones were 250°C. The extrudate was then pelletized. Correspondence to: E. Devaux (eric.devaux@ensait.fr). Journal of Applied Polymer Science, Vol. 86, 2416 –2423 (2002) © 2002 Wiley Periodicals, Inc.