Enhanced mechanical properties and fire retardancy of polyamide 6 nanocomposites based on interdigitated crystalline montmorillonite-melamine cyanurate

Polyamide 6 (PA6)-montmorillonite (MMT)-melamine cyanurate (MCA) nanocomposites were prepared by the incorporation of interdigitated crystalline MMT-MCA. Their morphologies were assessed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal stability measurement by thermogravimetric analysis, mechanical properties measurement by tensile tests, and fire retardancy measurement by limiting oxygen index testing and vertical burning testing (UL-94). The results indicate that MMT-MCA was homogeneously nanodispersed in PA6. Compared with PA6-MCA, the PA6-MMT-MCA nanocomposites showed enhanced thermal stability. The mechanical properties and fire retardancy show that the PA6-MMT-MCA nanocomposites with 5 wt % total loading of MMT-MCA reached UL-94V-2 rating (3.2mm) and significantly increased the tensile strength of PA6 up to 24.8 % with only 1 wt % MMT in PA6. Through the control the weight ratio of MMT and MCA in MMT-MCA, the Young's modulus of PA6 could be adjusted in a very wide range (300-1100 MPa) because of the dual role of the rigid MMT and nonrigid MCA layers. The reinforced mechanism of the mechanical properties was also investigated. Consequently, the PA6-MMT-MCA nanocomposites with a good nanodispersing ability, improved thermal stability, excellent mechanical properties, and good flame retardancy were obtained and could provide broad prospects for wider applications for PA6 materials. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46039.