Polybenzimidazole/Conductive Carbon Black Composite Driven at Low Voltage for High-Temperature Heaters

Carbon-based conductive polymer composites are thriving as promising electrothermal materials for a vast array of applications. However, the low working temperature (< 100°C) of most carbon-based conductive polymer composites due to the low melting point and inferior temperature resistance of polymer matrix severely restricts their high-temperature applications. Herein, a series of thin electric heating films composed of highly thermally stable polybenzimidazole (PBI) as polymer matrix and low-cost carbon black nanoparticles (Super P, SP) as conductive fillers are successfully developed to significantly increase the maximum working temperature as high as >200°C under relatively low applied voltage. The morphology, microstructure, electrical properties, and electrothermal behavior of the PBI/SP composites are systematically studied as a function of SP content. By introducing 15–25 wt.% SP conductive fillers, SP nanoparticles with uniform spatial dispersion are tightly anchored on the surface and tip of fiber-like villous PBI matrix, forming continuous highly conductive networks. However, the conductive filler content exceeds to 30 wt.%, and SP nanoparticles tend to locally clump together in aggregation, resulting in potential safety issues. Impressively, PBI/SP composite with 25 wt.% SP content (PBI/SP-25) exhibits superior electrothermal performance, including rapid temperature responsiveness, high maximum working temperature, superior heating uniformity, and remarkable electrothermal reproducibility. As an integrated thin-film heater for water boilers, PBI/SP-25 electrothermal film heats 100 ml of water to 99.5°C within 4 min at 25 V, demonstrating great potential in household electrical appliances.