Open microwave heating of polymer resin with dispersed carbon nanotubes using interdigital electrode film

Conventional microwave heating requires an expensive facility and its enclosed-type oven limits the size of curable products. This study proposes an open-type microwave heating of a polymer resin using microwaves produced by an interdigital electrode array film positioned between the composites and the mold. The proposed method has the advantages of reduced facility cost and applicability to large composite structures. The dispersion of carbon nanotubes (CNTs) in the resin also enables the use of a relatively low applied voltage for the heating at high temperature. This is because the CNT-filled resin has a high dielectric loss tangent compare with pure resin. A formula for predicting the amount of heat generated was developed based on the impedance frequency characteristics corresponding to the CNT content of the resin. It was observed that the generated heat increased with the CNT content owing to the increased dielectric loss tangent of the resin due to the dispersed CNT. It was particularly observed that a significant temperature increase occurred at 0.08 wt% CNT content as a result of the electrical percolation phenomenon. Moreover, a microwave heating experiment produced an amount of heat comparable to that predicted by the developed formula, and a heating efficiency of about 70%. The use of an interdigital electrode array film to heat a large area produced an inhomogeneous temperature distribution when a voltage was applied to all the electrodes. However, the application of selective heating together with the MIEA produced a more uniform temperature distribution.