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Keywords:

  • carbon nanofibers;
  • crystallization;
  • mechanical properties;
  • microstructure;
  • nanocomposites

Abstract

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The effects of carbon nanofibers (CNFs) on the microstructure and properties of semi-crystalline polymers were studied based on the preparation of poly(propylene) (PP) nanocomposites by a twin screw extrusion method. The crystallization behavior and morphology, as well as the thermal and mechanical properties of the CNF/PP nanocomposites, were characterized. Studies using differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) indicated that the CNFs promoted heterogeneous nucleation. The relative amount, crystallite size and distribution of different crystallites in PP varied because of the addition of CNFs, which affected the final properties of the nanocomposites. Meanwhile, the degree of crystallinity of the PP exhibited an increasing trend with the addition of CNFs, followed by moderate decreases at higher content. The dynamic mechanical analysis (DMA) test showed that the stiffness of the PP was enhanced as a result of the addition of CNFs. With increasing of CNF content, the flexural strength and modulus of the nanocomposites were enhanced continuously. Scanning electron microscopy (SEM) observations indicated that the CNFs were uniformly dispersed in the PP matrix. The effect of CNFs on the thermal stability was analyzed by comparing the thermogravimetric analysis (TGA) curves of the neat PP and CNF/PP composites. The thermal stability of PP composites at high temperature increased with enhanced CNF content.