Functionalized multi-walled carbon nanotubes (MWCNTs) via microwave-induced polymerization modification route, and polybenzimidazole (PBI) nanocomposite films containing 0.1-5 wt% functionalized MWCNTs were successfully synthesized. The functionalized MWCNTs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The results verify that the polymer was successfully grafted to the MWCNTs with a polymer layer that was several nanometers thick. The TGA results showed that the quantity of the attached polymer reached approximately 9.4 wt%. The mechanical properties of the nanocomposite films were measured by tensile test and dynamic mechanical analysis (DMA). The tensile test results indicated that the Young's modulus increased by about 43.9% at 2 wt% CNT loading, and further modulus growth was observed at higher filler loading. The DMA studies indicated that the nanocomposite films had a higher storage modulus than pure PBI film in the temperature range of 30-3008C, and the storage modulus was maintained above 0.82 GPa. Simulation results confirmed that the PBI nanocomposite films had desirable mechanical properties for use as a protective coating. POLYM. ENG. SCI., 51:1525-1532, 2011

Polybenzimidazole (PBI) nanocomposites containing 0.5-5 wt% vapor grown carbon nanofibers (VGNFs) were successfully synthesized by solvent evaporation method. Fracture morphology examination confirmed the uniform dispersion of VGNFs in the matrix. The mechanical properties of neat PBI and the nanocomposites were systematically measured by tensile test, dynamic mechanical analysis (DMA), hardness measurement and friction test. Tensile tests revealed that Young's modulus increased by about 36.7% at 2 wt% VGNFs loading, and further Correspondence to: Qing-Qing Ni; e-mail: niqq@shinshu-u.ac.jp modulus growth was observed at higher filler loadings. DMA studies showed that the nanocomposites have higher storage modulus than neat PBI in the temperature range of 30-350 C, holding storage modulus larger than 1.54 GPa below 300 C. Outstanding improvement of hardness was achieved for polybenzimidazole upon incorporating 2 wt% of VGNFs. The results of friction test showed that coefficient of friction of polybenzimidazole nanocomposites decreased with VGNFs content compared to neat PBI.