Role of Surface Physico-Chemistry on the Dielectric Behavior in LDPE Nanocomposites    (Pre-print to be submitted to IEEE-Transactions on Dielectrics and Electrical Insulation)    

The dielectric behaviour of nanocomposites strongly depends on its physico-chemistry. The changes to the bulk physico-chemistry due to filler infusion such as chemical-composition and physical morphology, and the corresponding effects on the dielectric properties including charge accumulation and breakdown strength are relatively well known. However, the effect of filler inclusion on the electrode-dielectric contact which dictates the charge injection is not clear. This work establishes a correlation between the surface-bulk physico-chemistry and the dielectric properties of LDPE-silica and LDPE-alumina nanocomposites through extensive experimentation. The bulk is characterized using Field Effect-Scanning Electron Microscopy (FE-SEM), Differential Scanning Calorimetry (DSC) and Fourier-Transform Infrared spectroscopy (FTIR) which provide information on the filler dispersion, physical morphology and chemical composition respectively. The charge injection surface is characterized using Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and Ultraviolet-Photoelectron Spectroscopy (UPS) to probe the geometrical features, physical morphology and electronic structures at the surface respectively. The space charge accumulation in all nanocomposites is obtained using the Pulsed-Electro-Acoustic (PEA) method and the dielectric withstand strength is obtained though AC breakdown analysis. The results indicate that the space charge accumulation and the breakdown strength are better correlated with the surface properties than the bulk.