Crystalline properties of injection molded polyamide-6 and polyamide-6/montmorillonite nanocomposites

This paper presents a study of the crystalline properties of injection molded samples of polyamide-6 (PA6) and polyamide-6/montmorillonite nanocomposites (PA6 MMT). Processing conditions and tool temperature during injection molding affect the crystal structure and the crystallinity of the samples. The samples were examined by X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM). PA6 presented both the α and γ structures, whose relative amount was dependent on the sample thickness. The most ductile γ structure predominated in PA6 MMT, although the XRD analyses suggested the occurrence of the α structure in the thickest sample. The melting peak from the DSC analyses also showed a significant influence of the thickness on the quality of the materials. The results confirmed that montmorillonite provides favorable conditions for the crystallization of the γ structure. The degree of crystallinity determined from DSC analyses was higher in the thickest samples (PA6 and PA6 MMT). The crystalline components of PA6 MMT were in all cases significantly more highly oriented than PA6, whereas the SAXS analyses showed that the lamellae (a suprastructure resulting from the organization of both the crystalline and the amorphous parts of the polyamide-6) in PA6 MMT were somewhat better oriented compared to the pure polymer samples.