Carbon nanotube induced double percolation in polymer blends: Morphology, rheology and broadband dielectric properties

Abstract

In this study, we investigate the effect of multi-walled carbon nanotube (MWCNT) on the rheology, morphology and broadband dielectric properties of polypropylene:polystyrene (PP:PS) blends (PP:PS—10:90, 50:50 and 90:10). Transmission electron microscopy showed that MWCNTs were localized at the interface and inside the PS phase, regardless of the polymer blend ratio. Employing scanning electron microscopy, we observed that addition of MWCNT led to a transition from dispersed to interconnected morphology for the blends with PS as minor phase (PP:PS/50:50 and PP:PS/90:10). We propose that the selective localization of MWCNT in PS and at the interface slowed down the breakup mechanisms, increasing the lifetime of PS/MWCNT elongated domains, thus decreasing the amount of PS/MWCNT needed to percolate in PP phase. In addition, it is proposed that MWCNT located at the interface act as bridges between PS/MWCNT domains, favouring the coarsening of PS/MWCNT domains. The dielectric properties of the polymer blends PP:PS/50:50 and PP:PS/90:10 confirmed that double percolation was achieved with increase in MWCNT content. This transition provided the possibility to tune dielectric properties of the PP:PS/MWCNT blends. The double percolated structure offered high imaginary permittivity, while the dispersed morphology presented low imaginary permittivity. In other words, this study reveals that manipulating blend morphology can lead to blends with capacitive or dissipative characteristics.