Tailoring the properties of PA6 into high-performance thermoplastic elastomer: Simultaneous reinforcement and impact property modification

Abstract

The effectiveness of the simultaneous addition of carbon nanotubes (CNTs) and maleic-anhydride-grafted-ethylene propylene diene (EPDM-g-MA) with a maleation content of 0.4 wt% was evaluated on the toughness of two grades of polyamide6 (PA6) with different molecular weight. The samples were fabricated in the presence or absence of 1.5 wt. % of CNTs by melt-mixing using an internal mixer where the PA6/EPDM-g-MA content weight ratio was 100/0, 90/10, and 80/20. Scanning electron microscopy (SEM) revealed a rougher fracture surface by EPDM-g-MA with high-molecular-weight PA6 (HPA6) than low-molecular-weight PA6 (LPA6) as noted from the finer EPDM-g-MA particles owing to higher PA6/EPDM-g-MA interfacial adhesion. A remarkable decrease in EPDM-g-MA droplet size accompanied by shape transformation was also observed by the introduction of CNTs. Transmission electron microscopy (TEM) exhibited more homogeneous and fine CNT dispersion in the HPA6-based nanocomposites as compared to LPA6-based ones. Tensile results revealed that CNTs can counteract the plasticizing effect of EPDM-g-MA on Young’s modulus of the PA6. Though the presence of CNTs was expected to sacrifice the ductility, HPA6-based nanocomposite maintained reasonable levels of ductility owing to the absence of CNTs agglomerations. The crystallization study showed the nucleating and reinforcing effect of CNTs in the formulated system. The rheological test confirmed the effective CNT/polymer interaction with substantially higher G' and η* for HPA6-based nanocomposites. Dynamic mechanical studies suggested higher toughening effectiveness of EPDM-g-MA on HPA6 over LPA6 by the lower tanδmax peak height and Tg for the PA6 phase.