Rheological properties of hyperbranched polymer/poly(ethylene terephthalate) reactive blends

The rheological properties in solution, in shear and in uniaxial elongation of poly(ethylene terephthalate) (PET) reacted together with hyperbranched polymers (HBPs) were investigated. Two different PET grades, of low and high molecular weights, were compounded with sub‐ to over‐stoichiometric concentrations of HBPs of second and fourth pseudo‐generation, and subsequently subjected to a solid‐state polycondensation (SSP). The formation of microgels, which occurs at high HBP concentration, gave rise to a large increase in melt elasticity and a related decrease in melt strength. At low HBP concentrations, the complex viscosity of the unreacted HBP/PET was considerably reduced, thus demonstrating a lubrication effect of the HBP molecules. During SSP, the intrinsic and shear viscosities exhibited a gradual increase, which was similar for both PET and HBP/PET blends, and was correlated to an increase in molecular weight, through linear‐chain extension and branching reactions. The elongational viscosity of the reactive blends was also increased as a function of reaction time, and this increase was much larger in the case of the HBP/PET blends. A 400% increase in melt strength of the PET was obtained by combining SSP and trace amounts of an HBP of second generation, without any decrease in drawability.     

Electrochemical properties of boron-carbon-nitride films formed by magnetron sputtering

The electrochemical behavior of B_1.0C_2.4N_1.0 thin film was investigated in acidic, neutral and alkaline solutions. The anodic polarization curve of the film in 1 M NaOH showed the anodic dissolution of the film. The curve of the film in 1 M HCl showed no anodic dissolution. The cathodic polarization curve in 1 M NaCl showed shift to a negative potential side, but the anodic polarization curve was the same as that of Pt. The anodic dissolution in 1 M NaOH depended on potentials, that is, no anodic dissolution was recognized in a potential range of −0.2 to 0.1 V but the dissolution rate increased with increasing potential in a range of 0.1-0.6 V. The anodic current density of the film is directly proportional to the dissolution rate at potentials higher than 0.1 V. The dissolution rate of the film was increased with increasing solution pH.     

On the modeling of electro-hydrodynamic flow in a wire-plate electrostatic precipitator

Modeling of the flow velocity fields for the electrohydrodynamic (EHD) flow in a wire-to-plate type electrostatic precipitator (ESP) was achieved. Solutions of the steady, two-dimensional Navier-Stokes equations have been computed. The equations were solved in the conservative finite-difference form on a fine uniform rectilinear grid of sufficient resolution to accurately capture the momentum boundary layers. The numerical procedure for differential equations was used by SIMPLEST [Michel, 2002], a derivative of Patankar’s SIMPLE algorithm, to bring rapid convergence. The Phoenics (Version 3.5.1) CFD code, coupled with Poisson’s and ion transport equations and electric body force in the momentum equation, developed in this study, was used for the numerical simulation. From calculations for the flow employing different flow models, the Chen-Kimk-ε turbulent model appeared to be the most appropriate choice to obtain a quantitative image of the resulting mean flow field and downstream wake flow of the rear wire, although this was obtained from a qualitative analysis due to the lack of experimental verification. The flow velocity field pattern showed a strong EHD secondary flow, which was clearly visible in the downstream regions of the corona wire despite the low Reynolds number for the electrode (Re_CW=12.4). Secondary flow vortices were also caused by the EHD with increases in the discharge current     

Synthesis and characterization of new functional poly(urethane‐imide) crosslinked networks

To synthesize new functional poly(urethane‐imide) crosslinked networks, soluble polyimide from 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′‐oxydianiline, and maleic anhydride and polyurethane prepolymer from polycaprolactone diol, tolylene 2,4‐diisocyanate and hydroxyl ethyl acrylate were prepared. Poly(urethane‐imide) thin films were finally prepared by the reaction between maleimide end‐capped soluble polyimide (PI) and acrylate end‐capped polyurethane (PU). The effect of polyurethane content on dielectric constant, residual stress, morphology, thermal property, and mechanical property was studied by FTIR, prism coupler, Thin Film Stress Analyzer (TFSA), XRD, TGA, DMTA, and Nano‐indentation. Dielectric constant of poly(urethane‐imide) thin films (2.39–2.45) was lower than that of pure polyimide (2.46). Especially, poly(urethane‐imide) thin films with 50% of PU showed lower dielectric constant than other poly(urethane‐imide) thin films did. Lower residual stress and slope in cooling curve were achieved in higher PU content. Compared to typical polyurethane, poly(urethane‐imide) thin films exhibited better thermal stability due to the presence of the imide groups. The glass transition temperature, modulus, and hardness decreased with increase in the flexible PU content even though elongation and thermal expansion coefficient increased. Finally, poly(urethane‐imide) thin films with low residual stress and dielectric constant, which are strongly affected by the morphological structure, chain mobility, and modulus, can be suggested to apply for electronic devices by variation of PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 113–123, 2006     

Solid extraction of caffeine and theophylline from green tea by molecular imprinted polymers

This paper involves a feasibility study on using molecular imprinted polymers as the sorbent materials in solid phase extraction for caffeine and theophylline from green tea. Two kinds of MIPs, with caffeine-theophylline mixture and pentoxifylline-theophylline mixture as the templates respectively, MAA as the monomer, EDMA as the crosslinker and ATBN as the initiator, were applied to this purpose. Mixture solution of caffeine and theophylline (1 Μg/ ml in acetonitrile) was applied to the solid extraction cartridges following a load, wash and elute procedure with acetonitrile, methanol, methanol-acetic acid (90/10, v/v) as the solvents, respectively. This solid phase extraction protocol was applied for extraction of caffeine and theophylline from green tea. Comparison between the results obtained with the MIPs cartridges and a traditional C₁₈ reversed-phase cartridge was made. It showed that the MIP-based sorbent on the solid phase extraction was comparable with that of C₁₈ material. HPLC analysis using a C₁₈ column (5 Μm, 250× 4.6 mm from Rstech corporation), methanol: water (60 :40, v/v) as the mobile phase at a flow rate of 0.6 ml/min was applied for the quantitative determination.     

Mobile phase composition for resolving whey proteins in reversed-phase high performance liquid chromatography

Reversed-phase high-performance liquid chromatography was successfully developed for the simultaneous and rapid separation for the main whey proteins, α-Lactalbumin and β-Lactoglobulin. This method consisted of a linear gradient of the two mobile phases of 0.1% trifluoroacetic acid in water and 0.1% trifluoroacetic acid in acetonitrile. The total run time for this separation was approximately 30 min, and α-Lactalbumin was eluted followed byβ- Lactoglobulin. The injection volume was fixed at 20 μl and the flow rate was 1 ml 1/min. The optimum mobile phase composition and gradient conditions to separate α-Lactalbumin and β-Lactoglobulin (A+B) were experimentally obtained at the 15 μm particle with a pore size of 300 Å on the linear-gradient mode.     

Desulfurization in a plate-type gas-lift photobioreactor using light emitting diodes

Hydrogen sulfide gas was removed in a 2-dimensional gas-lift reactor by the photosynthetic microorganismChlorobium thiosulfatophilum using light emitting diodes (LEDs) as a light source. LEDs saved light energy by 99% compared with the incandescent light source. The plate-type gas-lift reactor removed hydrogen sulfide five times better per unit mg of protein, and performed two times better in the maximum performance per unit luminous flux, compared with cylindrical fermentors.     

Fabrication of SiO2-ZrO2 composite fiber mats via electrospinning

(1 − x)SiO₂-(x)ZrO₂ (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite fibers having a tetragonal crystalline ZrO₂ were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and crystallization of ZrO₂ in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did not depend on the sintering temperature.     

Synthesis and properties of acrylonitrile-CR-methyl methacrylate graft copolymer

Graft copolymerization of acrylonitrile (AN) and methyl methacrylate (MMA) onto polychloroprene (CR) was carried out using benzoyl peroxide as initiator. The effects of mole ratio of AN to MMA, reaction temperature, reaction time, solvent, and initiator concentration on the graft copolymerization were examined. It was found that the thermal stability and weatherability of the AN—CR—MMA graft copolymer (ACM) were considerably better than those of CR.     

A porous mixed-valent iron MOF exhibiting the acs net: Synthesis, characterization and sorption behavior of Fe3O(F4BDC)3(H2O)3·(DMF)3.5

A new mixed-valent iron MOF, formulated as Fe₃O(F₄BDC)₃(H₂O)₃·(DMF)_3.5 (1), has been synthesized by using a perfluorinated linear dicarboxylate to link trigonal prismatic Fe₃(μ³-O)(O₂C–)₆ clusters. The structure refinement based on single crystal X-ray diffraction data collected from 1 reveals the material exhibits the acs topology with large channels along the crystallographic c-axis. Due to the presence of fluorine atoms the organic link, 2,3,5,6-tetrafluorobenzene-1,4-dicarboxylate (F₄BDC), has a 63° torsion angle between the carboxylate and aromatic planes, resulting in larger channels compared to those in the isoreticular material MOF-235. While few iron-based MOFs have demonstrated porosity, nitrogen and hydrogen sorption experiments carried out at 77 K proved the porosity of outgassed 1, which has a Langmuir surface are of 635 m²/g and a gravimetric capacity of 0.9 wt% of hydrogen at 1 bar.