Enhanced high-temperature polymer electrolyte membrane for fuel cells based on polybenzimidazole and ionic liquids

Polybenzimidazole (PBI)/ionic liquid (IL) composite membranes were prepared from an organosoluble, fluorine-containing PBI with ionic liquid, 1-hexyl-3-methylimidazolium tri?uoromethanesulfonate (HMI-Tf). PBI/HMI-Tf composite membranes with different HMI-Tf concentrations have been prepared. The ionic conductivity of the PBI/HMI-Tf composite membranes increased with both the temperature and the HMI-Tf content. The composite membranes achieve high ionic conductivity (1.6 × 10⁻² S/cm) at 250 °C under anhydrous conditions. Although the addition of HMI-Tf resulted in a slight decrease in the methanol barrier ability and mechanical properties of the PBI membranes, the PBI/HMI-Tf composite membranes have demonstrated high thermal stability up to 300 °C, which is attractive for high-temperature (>200 °C) polymer electrolyte membrane fuel cells.     

Effect of silanes on the morphology,hydrophobicity, and dynamical mechanical properties of polyimide/silica hybrid membranes

Polyimide (PI)/silica hybrid membranes with high contact angles were prepared through the in situ sol–gel process. The precursor, poly(amic acid) with controlled block chain length, was synthesized using 4,4′‐diaminodiphenyl ether (ODA), 3,3′,4,4′‐benzophenone‐tetracarboxylic dianhydride (BTDA) and 3‐aminopropyl‐trimethoxysilane (APrTMOS) or 3‐aminopropyldimethylethoxysilane (APDiMOS). And then, phenyltrimethoxysilane (PTS) or tetramethoxysilane (TMOS) or methyltrimethoxysilane (MTrMOS) was respectively, added to the above polyamic acid and mixed thoroughly. Following curing reaction, the PI/silica hybrid membranes with different cross‐linkages, silica content, and hydrophobic properties were prepared. The effect on the formation of PI imide ring during imidization reaction is increased as the increase of silanes content and characterized by frequency shiftment and absorbance ratio of Fourier transform infrared (FTIR) measurements. All the hybrid membranes show high transparency though with high silica contents. The storage modulus, tan δ, and damping intensity by DMA measurements are all correlated with silane content or block chain length. And all these membranes with silane content possess high contact angle as compared to pure PI without any silanes added and the contact angles increase with increasing the silane content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of thermally conductive photosensitive polyimide/boron nitride nanocomposites

A new thermally conductive photoresist was developed. It was based on a dispersion of boron nitride (BN) nanoflakes in a negative‐tone photosensitive polyimide (PSPI) precursor. 3‐Mercaptopropionic acid was used as the surfactant to modify the BN nanoflake surface for the dispersion of BN nanoflakes in the polymer. The thermal conductivity of the composite films increased with increasing BN fraction. The thermal conductivity of the PSPI/BN nanocomposite was up to 0.47 W m⁻¹ K⁻¹ for a mixture containing 30 wt % nanosized BN filler in the polyimide matrix. Patterns with a resolution of 30 μm were obtained from the PSPI/BN nanocomposites. The PSPI/BN nanocomposites had excellent thermal properties. Their glass‐transition temperatures were above 360°C, and the thermal decomposition temperatures were over 460°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Coating films prepared by photoreactions of the surface‐modified diamond powder and PET film with a binder agent

The surface‐modified diamond and PET film underwent photopolymerization rapidly with a binder agent to afford coating films of interpenetrating network (IPN) structure. The coating films thus formed exhibit higher tensile strength, thermal stability, and adhesion strength to the PET film. The inert surfaces of pristine diamond (PD) and PET film were modified by different chemicals and procedures to introduce epoxide and methacryloyl groups, respectively, on their surfaces. A coating agent consisting of an epoxide group containing modified diamond (called ED), a binder agent, and photoinitiators was prepared. After applying the coating agent to the substrate (a glass plate or a methacryloyl group containing PET film, MMA‐PET) and degassing under reduced pressure, the thin film of the coating agent was exposed to UV light (λ_max; 365 nm) at room temperature to yield a coating film of IPN‐structure. The tensile strength and thermal properties of the ED‐containing free coating film (called free film) increased with the amount of ED embedded, whereas the strength of the PD‐containing free film decreased with the amount of PD embedded. The adhesion strength of the coating film on the MMA‐PET improved significantly by the free radical polymerization of the methacryloyl groups on the MMA‐PET and the acrylate resin in the binder agent. The surface photoreactions of ED and MMA‐PET with the binder agent were confirmed by modeling. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Elucidating the dielectric properties of Mg2SnO4 ceramics at microwave frequency

This study investigated the potential applications of microwave dielectric properties of Mg₂SnO₄ ceramics in mobile communication. Mg₂SnO₄ ceramics were prepared using a conventional solid-state method. The X-ray diffraction patterns of the Mg₂SnO₄ ceramics revealed no significant variation of phase with sintering temperature. A maximum density of 4.62 g/cm³, a dielectric constant (?_r) of 8.41, a quality factor (Q × f) of 55,100 GHz, and a temperature coefficient of resonant frequency (τ_f) of −62 ppm/ °C were obtained when Mg₂SnO₄ ceramics were sintered at 1550 °C for 4 h.     

Kinetic and structural studies of the polymerization of N,N′‐bismaleimide‐4,4′‐diphenylmethane with barbituric acid

Both the isothermal and non‐isothermal polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) with barbituric acid (BTA) were investigated by the differential scanning calorimeter. The experimental results showed that the polymerizations of BMI with BTA were governed by the competitive Michael addition reaction and free radical polymerization mechanisms. Furthermore, the contribution of free radical polymerization becomes more important when the mole fraction of BTA decreases. ¹H NMR and ¹³C NMR measurements further support the coexistence of the Michael addition reaction and free radical polymerization mechanisms. A preliminary kinetic model that took into account the competitive Michael addition reaction and free radical polymerization mechanisms was developed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Low-temperature sintering and microwave dielectric properties of Nd(Co1/2Ti1/2)O3 ceramics using glass addition of oxides

The microstructures and microwave dielectric characteristics of complex perovskite Nd(Co_1/2Ti_1/2)O₃ ceramics with 60P₂O₅–15ZnO–5La₂O₃–5Al₂O₃–5Na₂O–5MgO–5Yb₂O₃ (PZLANMY) additions (1–4 wt%) prepared through the conventional solid-state route were investigated. It was found that Nd(Co_1/2Ti_1/2)O₃ ceramics can be sintered at 1210 °C owing to the sintering aid of PZLANMY-glass addition. At 1300 °C, Nd(Co_1/2Ti_1/2)O₃ ceramics with 1 wt% of PZLANMY-glass addition possess a dielectric constant (ε_r) of 27, a Q×f value of 64,000 GHz and a temperature coefficient of resonant frequency (τ_f) of ?29 ppm/°C. The PZLANMY-glass doped Nd(Co_1/2Ti_1/2)O₃ ceramics can find applications in microwave devices that require low sintering temperature.     

Synthesis of random or tapered solution styrene–butadiene copolymers in the presence of sodium dodecylbenzene sulfonate as a polar modifier

Random or tapered solution styrene–butadiene copolymer (SSBR) is very difficult to prepare in an isothermal batch process without the use of polar modifiers because of the diverse reactivity ratios of the styrene and the butadiene in hydrocarbon solvents. In the presence of polar modifiers, the random SSBR can be synthesized by anionic living polymerization with the variety of microstructures, which results in the change of glass transition temperature (T_g). This article will discuss the use of sodium dodecylbenzene sulfonate as a polar modifier in isothermal batch process that controls the microstructure of the SSBR resulting in a random as well as tapered SSBR with low T_g (?67°C to ?80°C). The T_g of SSBR was controlled by the styrene content rather than the microstructure of polybutadiene. Physical properties of SSBR compounding were discussed for tire tread applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nitroanilines enhancing the holographic data storage characteristics of the 9,10‐phenanthrenequinone‐doped poly(methyl methacrylate) photopolymer

This article describes an approach toward improving the characteristics of a photopolymer for holographic data storage application. The maximum diffraction efficiency (η_max) and dynamic range (M#) of 9,10‐phenanthrenequinone (PQ)‐doped poly(methyl methacrylate; PMMA) both improved significantly after co‐doping with one of three nitroanilines—N,N‐dimethyl‐4‐nitroaniline (DMNA), N‐methyl‐4‐nitroaniline (MNA), and 4‐nitroaniline (pNA). In particular, the value of η_max increased from 38% for the PMMA/PQ system to 72% for the PMMA/PQ/DMNA system (a 1.89‐fold improvement) and the value of M# increased accordingly from 2.7 to 7.3 (a 2.70‐fold improvement). Thus, the holographic data storage characteristics of PMMA/PQ photopolymers can be improved through co‐doping with nitroaniline compounds. We also investigated the mechanism of the nitroaniline‐induced improvement in optical storage performance using proton nuclear magnetic resonance and X‐ray photoelectron spectroscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effects of gas counter pressure and mold temperature variation on the surface quality and morphology of the microcellular polystyrene foams

In this study, we developed a foaming control system using the Gas Counter Pressure (GCP) combined with mold temperature control during the microcellular injection molding (MuCell) process and investigated its influence on the parts' surface quality and foams structures. The results revealed that under GCP control alone when GCP is greater than 10 MPa, part surface roughness for transparent polystyrene (PS) improved by 90%. When GCP increased, the skin thickness also increased, the weight reduction decreased and the average cell size reduced to about 30 μm. For black PS parts, when GCP is greater than 10 MPa, the part gloss reaches the same value as that molded by conventional injection molding. By increasing gas holding time, the cell density decreased and the cell size distribution became more uniform. The increase in amount of supercritical fluid foaming agent also increased the cell density. Applying mold temperature control alone with temperature in the range of 90–120°C (near T_g), the surface roughness improved by 65%. Increasing mold temperature decreased the skin thickness; however, the cell size distribution became significantly nonuniform. It was found that thin skin, small and uniform cell size as well as good surface quality can be achieved efficiently by simultaneous combining of GCP and mold temperature control. The proposed innovative approach may lead to a significant improvement and a more broad application for MuCell process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013