Effect of carbon nanotube addition on structure and properties for extrudates of high‐density polyethylene

We investigated the structure and properties of strands of high-density polyethylene (HDPE), containing multi-walled carbon nanotubes (MWCNTs) extruded from a capillary rheometer. Surprisingly, we found that the MWCNTs enhanced the chain orientation of HDPE, and that in the absence of MWCNTs, orientation relaxation occurred in the HDPE immediately after passing through the die. Conventional differential scanning calorimetry measurements indicated that MWCNT acts as a nucleating agent and raises the crystallization temperature 2 - 4 °C under quiescent condition. In the flow field, oriented MWCNTs behave like polymeric chain extended crystals “shish”, and greatly accelerate the flow-induced crystallization of the HDPE “kebab”. Consequently, the modulus was significantly increased in the flow direction. These findings demonstrate that the addition of MWCNTs is an effective method of enhancing the rigidity of HDPE.