Origin of non-universal percolation/scaling and universal non-Debye relaxation in PVDF/MWCNT polymer nanocomposites
Abstract
Polymer Nanocomposites (PNC) comprising polyvinylidene fluoride (PVDF)/Multi-walled Carbon Nanotubes (MWCNT) were studied. The structural composition and thermal stability were confirmed from XRD and DSC/TGA data, respectively. The extent of distribution of MWCNT in the PNC increases and the clustering of MWCNT also increases with an increase in the volume fraction of MWCNT (fMWCNT), as confirmed by FESEM. The PNC shows an insulator-to-metal transition (IMT), with both non-universal percolation threshold (fc) of fMWCNT=0.006 and scaling exponents [s=0.36±0.03,s′=1.26±0.1], respectively, attributed to adhesiveness/cold pressing and the higher aspect ratio/conductivity of MWCNT. Modulus spectroscopy confirms a non-Debye type universal relaxation behavior (β=0.54) only for the percolative sample due to Maxwell–Wagner–Sillars/interfacial polarization, while only dipolar relaxation was probed or the samples below fc. The fc with static effective dielectric constant ∼211 and low tan δ may be suitable for charge storage applications.
