Influence of processing conditions on the optical and crystallographic properties of injection molded polyamide-6 and polyamide-6/montmorillonite nanocomposites

This paper presents a study of the crystallographic and optical properties of injection molded samples of neat polyamide-6 (NPA6) and polyamide-6/montmorillonite nanocomposites (PA6-Mt) cooled at different temperatures (40, 60, 80 and 100 °C). Montmorillonite filler prevents the solid-to-solid phase transition α → γ of polyamide-6 crystals at ~ 90 °C by stabilizing the metastable γ structure. This γ structure presents higher crystal symmetry (pseudo-hexagonal) favoring epitaxy with the montmorillonite nanoplatelets, which also display hexagonal morphology. Moreover the montmorillonite does not affect the optical clarity of the reinforced polymer since its thorough exfoliation promotes smaller crystallite size.

Research Highlights
► The crystallinity of CPN increases with rising tool temperature after the injection.
► In neat polyamide-6, the lattice dilates with increasing cooling temperature.
► The montmorillonite yield to a better orientation of the polyamide-6 crystals.
► Translucency of CPN is connected to the good exfoliation of the clay mineral.