Melt rheological properties of nylon 6/multi-walled carbon nanotube composites

Nylon 6 (PA6) composites with different loadings of multi-walled carbon nanotubes (MWNT) were prepared by melt compounding technique. Melt rheological properties of PA6/MWNT composites were studied in linear viscoelastic response regions. The incorporation of MWNT into PA6 matrix resulted in higher complex viscosities (|η∗|), storage modulus (G′), loss modulus (G″), and lower loss factor (tan δ) than those of neat PA6, especially in low frequency region. The orientation of rigid molecular chains in the composites introduced by the addition of MWNT induced a strong shear thinning behavior and an increasing activation energy for the flow process. With the increase of MWNT loading, the composites experienced a transition from liquid-like to solid-like viscoelasticity. The decrease in the slope of the plot of log G′ versus log G″ with increasing MWNT loading suggested the microstructural changes of the polymer matrix due to incorporation of MWNT. At low frequencies, nonterminal solid-like rheological behavior of PA6 composites were observed and attributed to the formation of the network-like structures of MWNT in the polymer composites.