Improving the electrical conductivity of multiwalled carbon nanotubes‐containing micromoldings via in situ construction of electrically conductive networks

Abstract Microinjection molding (μIM) is characterized by high shearing and cooling rates, resulting in higher a degree of filler orientation which impairs the electrical conductivity (σ) of conductive filler‐containing polymer composites when compared with that of compression molding and conventional injection molding processes. In this study, polypropylene/polyamide 6/multiwalled carbon nanotubes (PP/PA6/CNT) composites were used as the model system to investigate how blending sequence, injection speed, and component mass ratios affected the morphology and σ of PP/PA6/CNT microparts. The results demonstrated that CNTs exhibited a higher affinity for the polar PA6 phase and they tended to be preferentially distributed in PA6 domains. The deformation and coalescence of CNT‐rich PA6 phase promoted the creation of an intact and continuous filler network structure along the flow direction under the influence of high shearing conditions in μIM. When the mass ratio of PP:PA6 was 70:30 and the concentration of CNT was 7 wt%, the micropart possessed the highest σ (1.2 × 10⁻⁶ S/m) when compared with their PP/CNT (4.4 × 10⁻⁹ S/m) and PA6/CNT (3.4 × 10⁻¹⁰ S/m) counterparts. Higher injection speeds resulted in higher degree of CNT orientation, which negatively affected the σ of subsequent moldings. This work established an approach for producing electrically conductive microparts that demonstrate promising applications in the fields of electronics, automotive, and microsystems among others. Highlights PP/PA6/CNT composites were used as model systems for microinjection molding. The electrical conductivity was improved by shear‐induced deformation of CNT‐rich phase. The properties of PP/PA6/CNT microparts were affected by process parameters.