Online Cure Monitoring of Carbon Nanotube/Polyimide Films

The work presents a method for online cure monitoring of polyimide nanocomposite films by measuring their electrical resistance. The polymer is mixed with 3% weight carbon nanotubes, and interdigital gold electrodes are structured on a silicon wafer to measure the electrical resistance. A series of drops in the electrical resistance was observed for each temperature step during the curing process. The first and most significant resistance drop occurred at 120 °C. This sudden change was attributed to the evaporation of the solvent since a weight change in the film was observed. A numerical model which computes the number of connected carbon nanotubes with respect to different solvent content also supports the theory of solvent evaporation. The presented method provides a tool to control the curing process of polymers. Moreover, the material could be also used for the fabrication of film polymer-based thermistors.