In Situ Temperature-Dependent Dielectric Characterization of Nanocomposites Heated With RF Energy

This article presents a new method for dielectric characterization as a function of temperature and frequency for nanomaterial-loaded polymers, while they are heated with radio frequency (RF) energy. Specifically, the dielectric constant and electrical conductivity of polymers with conductive nanomaterials are measured in the RF frequency range (up to a few hundreds of MHz), while the material is undergoing a curing reaction using a high-power RF energy source. The nanomaterials act as susceptors for RF energy to facilitate heating to the desired temperatures for processing and curing polymers. Measurement techniques were developed to enable simultaneous
in situ
RF heating and characterization of the polymer. Since some polymers used in this work are liquids at room temperature, such samples are placed in an alumina crucible located at the end of a microstrip-type applicator. Temperature is monitored using an FLIR thermal camera. Multiphysics simulations are used to help develop the appropriate applicator for RF heating and dielectric measurements. An appropriate calibration procedure along with a circuit model to enable extraction of the dielectric constant and electrical conductivity from the measured reflection coefficient is introduced.