Estimation of Interphase Permittivity and Interphase Thickness in Epoxy based Nanocomposites using Electrostatic Force Microscopy

Inclusion of a small quantity of metal oxide nano-fillers significantly improves electrical and other properties of a polymer dielectric; literature attributes this improvement to the interphase region between matrix and nano-particle. Till date, direct observation of the interfacial region has not been possible. The current work explores the possibility of detecting the interphase using Electrostatic Force Microscopy (EFM). Experiments are performed on epoxy-based nanocomposites with barium titanate nano-fillers. EFM detects the phase shift around a single nanoparticle embedded in the polymer matrix. A computational model, simulating the experimental conditions, is used to generate the EFM phase shift numerically. This is matched with the experimental EFM phase image, to obtain an estimate of the interphase permittivity and thickness. Statistical analysis of particle size in powder form and when embedded in the epoxy lends credence to the estimates obtained.