A study of the thermal,dynamic mechanical,and tribological properties of polyphenylene sulfide composites reinforced with carbon nanofibers

The thermal, dynamic mechanical, and tribological properties of polyphenylene sulfide (PPS) composites reinforced with carbon nanofiber (CNF) were studied. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to study the viscoelastic properties and thermal transitions. In order to study the tribological properties, friction and wear tests in a pin-on-disk configuration were performed. The changes in melting point, crystallization temperature, and glass transition temperature were found to be small as a result of reinforcement. Steady state wear rates of the reinforced composites sliding against the counterface of roughness 0.13–0.15 μm Ra were significantly lower than that of the unreinforced PPS. When the composites were tested against the smoother counterface of 0.06–0.11 μm Ra, the wear rates were higher. The coefficient of friction in all the cases was not practically affected by the presence of CNF. The transfer films formed on the counterface during sliding were examined by optical microscopy and atomic force microscopy (AFM). The variation of wear is discussed in terms of the texture and topography of transfer film.     

Conductivity of carbon nanofiber/polypyrrole conducting nanocomposites

Carbon nanofiber (CNF) / Polypyrrole (Ppy) composite materials were fabricated by two newly invented processes - filtering, washing and drying the mixture of CNF dispersion and Ppy-NMP solution (FWP process) and heating an aqueous solution of CNF (SH process). CNF/Ppy composite materials have never been reported before in any other research papers. Conductivities of the composite films were obtained by using a four-probe method. To compare the conductivity of CNF/Ppy with that of a pure single-walled carbon nanotube (SWNT), SWNT films were also fabricated and voltage was measured. SEM images were taken for both a surface and a cross-section of composite samples fabricated by the two processes. The CNF/Ppy by FWP was a little brittle because of the low solubility of Ppy in the NMP, and on the other hand, the same material by SH became flexible enough. The conductivity of the pure SWNT film was as high as double the similar case. The conductivity of the pure SWNT film was 20.11 S/cm and 0.013 cm thick. The CNF/Ppy composite films with the thicknesses of 0.062 cm and 0.085 cm gave a conductivity of 63.32 S/cm and 40.57 S/cm, respectively, which are higher than that of the pure SWNT film or SWNT/Polyaniline (PANi) film. The good conductivity of CNF/Ppy composites shows the improved potential for developing the materials for a small actuator. This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho Cheol Kim received a B.S. degree in Mechanical Engineering from Yonsei University in 1985 after his military service. He then received his M.S. from Georgia Tech in 1989 and Ph.D. from U. of Illinois at Urbana-Champaign in 1994. Dr. Kim is currently a Professor at the School of Mechanical Engineering at Kyungpook National University (KNU) in Daegu, Korea. He is currently serving as an associate editor of the Transactions of the KSME A. Shuai Zhang is a Ph.D. candidate. He received his B.S. in 2003 from HIT in China and M.S. in 2006 from KNU.