Infrared spectroscopy studies of structure and orientation in clay-reinforced polyamide-6 nanocomposites

Infrared (IR) spectroscopy was used to study the surface (by means of external reflection) and the bulk (by means of transmission measurements on microtomed slices) of specimens obtained by injection moulding of a commercial polyamide-6 clay-based nanocomposite material (NCH = nylon clay hybrid) at different mould temperatures and with different part geometries. Comparisons were made with equivalent non-reinforced polymer (PA-6). For the PA-6, the mould temperature influences the crystalline structure, with the gamma phase predominating at 50degreesC and the alpha phase at 80degreesC. However, in the NCH material the gamma phase is favoured, even at 80degreesC. In all cases the crystallinity increases on going from the surface to the core. The polymer chains are oriented in the flow direction, and the orientation is higher for parts with more elongated shapes. It does not vary greatly across the part thickness, except for a thin surface layer, where it is significantly higher. Both at the surface and in the bulk, the crystalline phase orientation is higher for the NCH than for the PA-6.