Graded Composites of Polyamide/Carbon Nanotubes Prepared by Laser Sintering

In this study, the mechanical and electrical properties of graded composition material (GM) were investigated in order to evaluate the effects of the addition of multi-walled carbon nanotubes (MWCNTs) to a polyamide 12 (PA12) matrix in different proportions. A graded component of PA12/MWCNTs was designed and manufactured by selective laser sintering (SLS) and variations in the morphology as well as in the mechanical and electrical properties were observed. The effect of different proportions of MWCNTs in the PA12 was investigated by microscopy, flexural test and resistivity measurements. The addition of 0.5 and 1.0 wt% of MWCNTs promoted an increase in the composite strength and flexural modulus. A significant reduction in the resistivity was verified with the addition of 3.0% of MWCNTs in the polyamide matrix. The mechanical and electrical behavior presented by the PA12/MWCNT composites suggests that the percolation concentration is around 3 wt%, when an effective inter-nanotube contact seems to be reached, improving the electrical conductivity but reducing the mechanical strength. A GM component with an MWCNT concentration gradient along the vertical axis was designed and manufactured by SLS. A gradual controlled variation in the composition of GM component leads to variations in the microstructure as well as in the mechanical and electrical properties.