Microstructure and properties of polypropylene composites filled with silver and carbon nanotube nanoparticles prepared by melt-compounding

Polypropylene reinforced with silver and multi-wall carbon nanotubes (MWNTs) particles were prepared by melt-compounding process. The morphology of PP nanocomposites was characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy. Moreover, the electrical properties of binary PP/Ag and ternary PP/Ag/MWNT nanocomposites were examined. Microstructural examination revealed that the Ag nanoparticles acted as nucleation sites for PP, and induced the formation of β-form PP crystals. Therefore, PP transcrystals were formed adjacent to individual Ag particles and clusters. These insulating PP transcrytals blocked the conductive pathways in PP/Ag nanocomposites, thereby degrading their electrical properties. Annealing treatment of PP/Ag nanocomposites led to the formation of voids and microcracks in PP matrix as a result of structural transformation of β- to α-form PP. Such transformation also deteriorated the electrical properties of PP/Ag nanocomposites. The addition of a small amount of MWNT promoted significantly the electrical properties of PP/Ag/MWNT hybrid composites.