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ABSTRACT:Various output heaters were extruded with acetylene black-filled platinum-catalyzed silicone rubber. The resistivity-temperature behavior of extruded heaters exhibited a positive-temperature coefficient (PTC) effect without any negative-temperature coefficient (NTC) effect. Resistivity and thermal reproducibility of the extruded heaters were investigated during heating and cooling cycles at an applied voltage of 220 V. These heaters initially showed poor reproducibility of resistivity during the repeated cycles and this effect increased significantly as the acetylene black content decreased. PTC effect and electrical reproducibility were improved significantly during the thermal ageing process.

PMMA (polymethylmethacrylate), which is miscible with hexafluoropropane dianhydride (6FDA)‐based polyimide, was grafted onto MWNTs surfaces to enhance their dispersion relative to that of pristine MWNTs. The electrical conductivity of the 6FDA‐based composite revealed percolation threshold behavior, and the 6FDA‐4,4′‐(hexafluoroisopropylidene)diamine, (6FpDA):3,5‐diaminobenzoic acid (DABA)/PMMA‐g‐MWNT composite showed a higher percolation threshold concentration and a slightly lower critical exponent compared with those of the 6FDA‐6FpDA composite. Because of the weak interaction energies between 6FDA‐6FpDA:DABA and PMMA, agglomerated domains were formed. Also, the weak interaction energies of the 6FDA‐6FpDA:DABA led to a larger reduction in the normalized transmittance compared with that seen in the 6FDA‐6FpDA composite. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

A novel organic/inorganic composite membrane synthesized with sulfonated multiwalled carbon nanotubes (s-MWNTs) and sulfonated polyetherimide (s-PEI) is prepared for use in a direct methanol fuel cell (DMFC). A solution casting method was used to prepare s-MWNT/s-PEI membranes (SPEI membranes) with various s-MWNT contents. This composite membrane showed not only low methanol crossover and water swelling but also enhanced mechanical properties. The IEC and proton conductivity of SPEI membranes were increased by incrementing their s-MWNT content. This is because the number of sulfonic acid groups (SO 3 À ) increases as s-MWNTs are added. The water uptake of SPEI membranes increased as s-MWNT content was increased due to the hydrogen bonded interaction between sulfonic groups and carboxylic groups in s-MWNTs and water molecules. However, the water uptake of SPEI membranes is remarkably low, compared with Nafion membranes. The methanol permeability of the SPEI membranes (8.8 Â 10 À8 cm 2 s À1 ) in this study was also lower than that of the Nafion membrane. Therefore, SPEI membranes were expected to have potential applications in DMFCs. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: E467-E477, 2012