Phase morphology and enhanced thermal/mechanical properties of polyamide 46/graphene oxide nanocomposites

Polyamide 46 (PA 46)/graphene oxide (GnO) nanocomposites were successfully prepared using a solution mixing technique. GnO was obtained by modifying pristine graphite through oxidation treatment along with ultrasonication in formic acid. Raman spectroscopy showed a high intensity ratio of D to G bands (ID/IG = 0.96) for the oxygen-functionalized graphite, confirming efficient modification of pristine graphite. Transmission electron microscopy demonstrated nanoscale dispersion of GnO within the PA 46 matrix. Polarized light microscope observations showed that the inclusion of GnO led to the formation of small PA 46 crystallites rather than large crystalline spherulites of neat PA 46. Differential scanning calorimetry results indicated that adding a small amount (i.e., 0.25 wt.%) of GnO noticeably aided the nucleation of PA 46, which corresponded to the morphological observations. The presence of GnO also induced PA 46 crystals with higher stability, thus reducing the possibility of crystal annealing during the heating scans. The melting temperature of PA 46 in the nanocomposites increased to higher temperatures. As confirmed through in-situ x-ray diffraction experiments, the Brill transition of PA 46 crystals shifted from approximately 160 °C to 180 °C with the inclusion of GnO. Dynamic mechanical analysis demonstrated the rigidity (storage modulus) enhancement of PA 46 after GnO additions.