Thermally stable polybenzimidazole (PBI)-based composite films filled with different pristine multiwalled carbon nanotube (MWCNT) contents of 0.0-10.0 wt% were manufactured by a facile solution casting, and their microstructural features, thermal and electrical properties were investigated as a function of the MWCNT content. Electron microscopic images and FT-IR spectra of the composite films confirmed that each MWCNT was wrapped with PBI chains by pi-pi interaction and thus they were well dispersed in the PBI matrix. Thus, the electrical resistivity of the composite films decreased considerably from similar to 10(7) Omega cm to similar to 10(-1) Omega cm with the increment of the MWCNT content, especially at a certain percolation threshold of similar to 0.25 wt% MWCNT. The composite films containing above 0.3 wt% MWCNT contents exhibited excellent electric heating performance. For instance, the composite film with 10.0 wt% MWCNT exhibited low temperature growth/decay time constant of similar to 1 s, stable maximum temperatures of 40-220 degrees C, and high electric power efficiency of similar to 732 mW/degrees C under the relatively low applied voltages of 5-25 V. Thermogravimetric analysis revealed that the composite films were thermally stable up to similar to 450 degrees C under air environment. It is thus reasonable to contend that PBI/MWCNT composite films can be used as high performance electric heating materials in emerging application areas. (C) 2015 Elsevier Ltd. All rights reserved.