Synthesis of poly (hexamethylene terephthalamide)-co-polycaprolactam/modified montmorillonite nanocomposites with enhanced mechanical properties and lower water absorption rate by in-situ polymerization

In this study, poly (hexamethylene terephthalamide)-co-polycaprolactam (PA6T/6) /organic montmorillonite (OMMT) composites were synthesized through melt-blending and in-situ polymerization. The interlamellar spacing of the montmorillonite in the composites prepared by in-situ polymerization (iPM) is larger than that of those composites prepared by melt-blending (mPM) shown in X-ray diffraction (XRD) curve, indicating intercalation of clay occurred in iPM composites. The morphology of mPM composites and iPM composites were observed taking advantage of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both methods reveal that well-organized intercalation and exfoliation structure were formed in iPM composites while the clay in mPM composites tends to self-aggregate, which corresponded well with the XRD results. In violent contrast to mPM composites, the tensile strength of iPM composites was largely increased to 95.1 MPa with 1 wt% of OMMT content compared to that of the neat PA6T/6 (69.8 MPa). In addition, the water absorption is also alleviated by 26.8% at room temperature (23 °C) and 23.6% at high temperature (90 °C) for iPM composites while no obvious difference is observed for mPM composites, which is in consistent with the results of water vapor transmission rate.