Balancing the strength and toughness of polypropylene/carbon nanotube nanocomposites by shear and high‐temperature annealing

Abstract Melt‐mixed polypropylene (PP) and multi‐walled carbon nanotubes (CNTs) are molded by compression molding, conventional injection molding, and interval injection molding (IntM). IntM can provide high‐shear stress promoting the dispersion of CNTs and forming many shish‐kebab structures, which can improve the strength at the cost of toughness. Meanwhile, high‐temperature annealing (HTA) can be finished in 3 min and can release free molecular chains, enhance orientation, and further promote the dispersion of CNTs, thus improving toughness at the expense of strength. Therefore, in this work, IntM and HTA are combined, which can balance and enhance both the toughness and strength of PP‐CNT nanocomposites. For different CNT contents, the enhancement effect also differs. The combined IntM and HTA do not require replacing existing production equipment, so this research can provide a more economical and practical approach to enhancing PP‐CNT nanocomposites. Highlights HTA can be finished in 3 min and promote the dispersion of CNT agglomerates. IntM can enhance the orientation and dispersion of CNTs. Combined IntM and HTA can enhance and balance toughness and strength.