MWCNT reinforced polyamide-6,6 films: preparation, characterization and properties

Composite films of Polyamide-6,6 (PA66) and multi-walled carbon nanotubes (MWCNTs) were prepared by a combination of solution casting followed by compression molding techniques. Both unfunctionalized (u-MWCNTs) and functionalized nanotubes (f-MWCNTs) were used in this study. The functionalization involved direct solvent-free amination of MWCNTs with hexamethylenediamine. Thermogravimetric analysis was used to observe the changes in the nanotubes upon functionalization and morphological features of the resulting composite films were studied using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The crystallinity changes by incorporation of the u-MWCNTs and f-MWCNTs in the PA66 matrix were studied by wide angle X-ray scattering and differential scanning calorimetry. The f-MWCNT/PA66 film showed an improvement of -43% in maximum tensile stress (MTS) and-32% in Young's modulus over pristine PA66 film, while at a similar loading of 0.5 wt%, the f-MWCNT/PA66 film showed -15% increase in MTS and -16% increase in modulus over the u-MWCNT/PA66 film. Dynamic mechanical analysis indicated significant difference in the small-strain mechanical properties between the MWCNT-filled and unfilled PA66 at the very low MWNT loadings that were tested and supported the tensile results. The water absorption trend of the composite films showed dramatic improvement over the neat film.