Nanoindentation behaviour of layered silicate filled spent polyamide-12 nanocomposites

This paper deals with the nanoindentation behaviour of spent polyamide-12 and spent polyamide-12/layered silicate filled nanocomposites. Layered silicates at I wt.%, 3 wt.% and 5 wt.% were used as filler in spent polyamide-12 and the nanocomposites were prepared by using a single screw injection moulding technique. The interlayer d-spacing, interlamellar structure and surface morphology were investigated by wide angle x-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The effect of various concentrations of layered silicate reinforcement on the nanomechanical properties was investigated by a nanoindentation test method. The nanohardness increased from 0.156 GPa for neat spent PA-12 up to 0.338 GPa for 5 wt.% spent PA-12/nanocomposite. Similarly, reduced modulus of neat spent PA-12 increased by 73% with the incorporation of 5 wt.% layered silicate. Different levels of nanofiller dispersion characterised using XRD and TEM correlated strongly with improvements in nanohardness properties. The much improved nanohardness and modulus values are related to the intercalated and exfoliated structure of spent PA-12/nanocomposites. The reutilisation of spent materials such as spent PA-12 has great potential for economic and environmental benefits. (C) 2011 Elsevier Ltd. All rights reserved.