Simultaneous Enhancement of the Conductivity and Toughness for Polyamide 66 Nanocomposites by Regulating the Hydrogen Bond and Introducing Microcellular Structures

High-toughness and high-conductivity polyamide 66 (PA66)-based composites and foams were successfully fabricated by regulating the hydrogen bond and introducing a microcellular structure. The PA66/carbon nanotube (CNT) and PA66/3-pentadecylphenol (PDP)/CNT composites were prepared via melt blending. The conductivity tests showed that the introduction of PDP reduced the percolation threshold of PA66/PDP/CNT by 23.3% to 4.6 vol % and increased the maximum conductivity by 53 times to 1.4 S/cm, in comparison to those of PA66/CNT. This was due to the decrease in crystallinity and crystal size as well as the increase in the γ-phase content of the composites caused by the hydrogen bonding between PA66 and PDP, as well as the decrease in viscoelasticity of the composites caused by the plasticizing effect of PDP, thereby improving the connectivity of the conductive network. By introduction of microcells into the composites using supercritical CO2 as the blowing agent, the electrical conductivity and tensile toughness of the composite foams under low CNT loadings were simultaneously enhanced compared to the corresponding solid composites.