Structure and Dynamic Mechanical Properties of Melt Intercalated Polyamide 6—Montmorillonite Nanocomposites Arthur N. Wilkinson,* 1 Zakaria Man, 1a John L. Stanford, 1 Petri Matikainen, 2b Mark L. Clemens, 2 Graham C. Lees, 2 Christopher M. Liauw 2 1 University of Manchester, School of Materials, Materials Science Centre, Grosvenor Street, Manchester, M1 7HS, UK 2 Dalton Research Institute, Department of Chemistry and Materials, Manchester Metropolitan University, Manchester, M1 5GD, UK E-mail: arthur.wilkinson@manchester.ac.uk Received: April 5, 2006; Revised: June 2, 2006; Accepted: June 7, 2006; DOI: 10.1002/mame.200600150 Keywords: morphology; nanocomposites; organoclay; polyamides Introduction Polymer-layered silicate nanocomposites (PLSN) have attracted considerable scientific and commercial interest over the past decade. [1–5] The main driver for this is the potential for significant enhancement in mechanical properties, [1–5] com- bined with reductions in permeability [6] and flammability, [7] resulting from the incorporation of only a few weight percent (wt.-%) of a nanoscale lamellar filler into a polymer. Thus, PLSN have lower densities than traditional polymer compo- sites and also tend to exhibit smaller reductions in impact resistance and surface finish. The polymer composites studied Summary: Polymer-layered silicate nanocomposites (PLSN), based on polyamide 6 (PA6) and montmorillonite (MMT) modified with an octadecylammonium salt, were produced via melt compounding in a co-rotating twin-screw extruder. Wide angle X-ray diffraction (WAXD) and TEM revealed a PLSN containing 3.3% by weight (wt.-%) of MMT to exhibit a mixed exfoliated/intercalated morphology, consisting mainly of individual silicate lamellae together with some intercalated stacks, resulting in a mean value of 1.8 lamellae per particle. In contrast, a PLSN containing a higher level of 7.2 wt.-% MMT exhibited a more ordered intercalated structure, consisting mainly of a distribution of lamellae stacks with a mean value of 3.8 lamellae per particle. The dispersion of MMT in the PLSN generated very large polymer–filler interfacial areas, resulting in significant increase in the volume of constrained PA6 chain segments. Consequently, significant changes in the ratio of a/g crystallites and in the thermal behaviour of the matrix PA6 were observed during WAXD, DSC and dynamic-mechanical thermal analysis (DMTA) studies of the PLSN. In particular, damping data from DMTA showed relaxations between T g and T m resulting from amorphous polymer chain segments constrained at the polymer–filler interface, indicating the formation of a continuous phase of constrained polymer. In contrast, a PA6 microcomposite formed using unmodified MMT generated much lower polymer–filler interfacial area, with most of the MMT residing within large, poorly wetted aggregates. Consequently, changes to the thermal behaviour of the matrix PA6 were much less significant than those induced in the PLSN. Shear storage modulus (G 0 ) versus temperature data for the matrix PA6, the 5T and 10T PLSN and the 5P micro- composite. Macromol. Mater. Eng. 2006, 291, 917–928 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Full Paper DOI: 10.1002/mame.200600150 917 a Current address: Perlos (Beijing), Beijing, People’s Republic of China b Current address: Universiti Teknologi Petronas, Perak, Malaysia