Comparison of PVDF/PVAc/GNP and PVDF/PVAc/CNT ternary nanocomposites: Enhanced thermal/electrical properties and rigidity

Graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) were incorporated individually into miscible polyvinylidene fluoride (PVDF)/polyvinyl acetate (PVAc) blend to obtain ternary nanocomposites. Optical and electron microscopy images showed that the CNTs were more randomly dispersed within the blend matrix than the GNPs. DSC results illustrated that the CNTs exhibited higher nucleation efficiency than the GNPs for PVDF crystallization in the composites. In addition, the CNTs more evidently accelerated the isothermal crystallization of PVDF in the composites than the GNPs. The presence of PVAc decreased the melting temperature of PVDF; GNP or CNT addition induced higher PVDF melting temperatures than the blend. XRD results demonstrated no change in α-form crystals of PVDF in the blend and composites. The thermal stability of PVDF in the blend was improved after GNP or CNT incorporation; GNPs produced slightly more improvement than CNTs. The storage modulus (rigidity) of 1.5 phr CNT- or GNP-added composites increased by 28.7% or 73.8% (at 25 °C), respectively, compared with that of the blend matrix. The presence of either GNPs or CNTs reduced the electrical resistivity of the parent blend, with the CNTs exhibiting evidently higher efficiency than the GNPs. The electrical and rheological percolation thresholds ((pseudo)network structure development) of the CNT-added composites were determined at 0.3-0.5 phr and 1 phr loading, respectively. The GNP-added composites showed no percolations due to lesser random dispersion of GNPs within the blend matrix.