Study on the electrical and rheological percolation threshold of single-walled carbon nanotube-reinforced thermoplastic elastomer based on polypropylene/ethylene–propylene–diene monomer nanocomposite

Abstract

The rheological and electrical percolation threshold of single-walled carbon nanotube (SWNT)-reinforced thermoplastic elastomer based on polypropylene/ethylene–propylene–diene monomer (PP/EPDM; 80/20) nanocomposite was investigated by melt-mixing process. The rheological properties revealed that the addition of SWNT increased the shear stress and shear viscosity. Both PP/EPDM and its nanocomposites exhibited non-Newtonian behavior. It was also found that the materials experience a fluid–solid transition at 0.5 wt% SWNT. The steady shear behaviors and die swell decreased with increasing temperature. The maximum flow activation energy corresponding to the minimum die swell was also observed. The scanning electron microscopic morphology of the PP/EPDM/SWNT nanocomposites showed that the EPDM particles were dispersed through PP and the size of dispersed phase decreased with the introduction of SWNT to 0.5 wt%. The electrical percolation threshold was formed at approximately 1 wt% of SWNT. In addition, difference between electrical and rheological percolation thresholds was observed due to the nanotube–nanotube distance after the formation of the percolating network.