Growth of carbon nanotubes on silica microparticles and their effects on mechanical properties of polypropylene nanocomposites

• Multiscale fillers were synthesized by growing carbon nanotube on silica particles.
• Appropriate crystallinity of nanotubes with high production yield was demonstrated.
• Rheological behavior of the CNT–silica–polypropylene composites was investigated.
• Significant improvement was achieved in mechanical property of multiscale composite.
• Two micromechanical models were employed to discuss reinforcement effects.

Multiscale fillers were synthesized through growing carbon nanotubes (CNT) on silica microparticles via catalytic chemical vapor deposition process. The characterization of as-synthesized CNT demonstrated appropriate crystallinity and purity of nanotubes with a production yield as high as 400% according to the catalyst-silica weight. The CNT–silica fillers were incorporated within polypropylene (PP) matrix by melt-mixing process to investigate the rheological and mechanical properties of fabricated nanocomposites. In spite of the inclusion of multiscale fillers up to 2 wt.%, the rheological behaviors of the nanocomposites were comparable to the pristine PP with moderate enhancement. An improvement by more than 35% was achieved for elastic modulus and tensile strength of nanocomposites, which was discussed by employing two micromechanical modeling approaches. The strengthening effects of CNT–silica reinforcement on impact strength of PP was revealed by impact tests and was illustrated through fractography of nanocomposites.

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