Effect of shear element and process in screw‐based extrusion printer of polypropylene/carbon nanotubes composite

Abstract Granular polypropylene (PP) and carbon nanotube (CNT) masterbatch are melt‐mixed and printed using a custom‐built screw extrusion printer. Compared to the conventional screw printer (CSP), the shear screw printer (SSP) with a shear element at the end of the screw, can apply higher shear stress to the melt. Meanwhile, the SSP has a wider screw speed to match the printing speed, and the screw speed is positively correlated with the shear stress. The shear stress can promote the dispersion of CNTs, thus improving the tensile strength. However, the circumferential shear inside the screw, superimposed on the linear shear at the nozzle, makes the warping deformation of the part more pronounced. The effects of the shear element and CNTs on thermal stability, crystal structure, and electrical conductivity are also discussed. Finally, a single‐screw printer has achieved mixing capability and can simplify the process of nanocomposite fabrication. Highlights A shear element used to provide high shear in screw‐based extrusion printers. Shear screw promotes CNT dispersion, simplifying the printing process. Increased CNT dispersion improves mechanical strength and thermal stability. CNTs can prevent warping and deformation of printed parts.