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991.
Novel nanoparticles, polymer‐particle coupling agents, and functionalized polymers are being developed to enhance the performance of particle‐reinforced polymer systems such as advanced rubber compounds for automobile tires. Understanding the complex rheological behavior of rubber is critical to providing insights into both processability and end‐use properties. One unique aspect of the rheology of filled elastomers is that the incorporation of particles introduces a hysteretic softening (Payne effect) at small dynamic strains. This study demonstrates that this nonlinear viscoelastic behavior needs to be considered when attempting to correlate steady shear response (Mooney viscosity) to oscillatory shear measurements from test equipment such as the Rubber Process Analyzer (RPA). While a wide array of unfilled gum elastomers show good correlation between Mooney viscosity and dynamic torque from the RPA at all of the strain amplitudes used, rubber compounds containing silica and carbon black particles only exhibit good agreement between the two measures of processability when the oscillatory strain amplitude is high enough to sufficiently break up the filler network. Other features of the filler network and its influence on nonlinear rheology are considered in this investigation, including the effects of polymer–filler interactions on filler flocculation and the use of Fourier transform rheometry to illustrate the “linear‐nonlinear dichotomy” of the Payne effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40818. 相似文献
992.
Selective adsorption of CO2 over N2 is important in the design and selection of adsorbents such as metal‐organic frameworks (MOFs) for CO2 capture and sequestration. In this work, single‐component and mixture adsorption isotherms were calculated in MOFs using grand canonical Monte Carlo (GCMC) simulations at conditions relevant for CO2 capture from flue gas. Mixture results predicted from single‐component isotherms plus ideal adsorbed solution theory (IAST) agree well with those calculated from full GCMC mixture simulations. This suggests that IAST can be used for preliminary screening of MOFs for CO2 capture as an alternative to more time‐consuming mixture simulations or experiments. © 2011 Canadian Society for Chemical Engineering 相似文献
993.
Karel Grohman Randall Cameron Yang Kim Wilbur Widmer Gary Luzio 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(3):395-407
BACKGROUND: Approximately 0.7 ? 1 × 106 dry tons of citrus processing waste (CPW) are produced annually in the United States. CPW is sold as animal feed but often the financial return does not exceed the production cost. Polysaccharides comprise 40% of the total dry matter of which pectin is the major component. CPW was steam treated to extract pectin fragments (PFs) as a value added co–product prior to fermentation of other sugars for biofuels production. RESULTS: PFs were extracted in high yields, along with polymeric arabinans, galactans and arabinogalactans. The extracted polysaccharides ranged in size from small oligomers to polymers of ～700 000 g mol?1. Acidified treatments led to greater fragmentation of water soluble polysaccharides, but did not enhance fragmentation of pectins to small oligomers (> 30 mer). Methylesterified PFs, arabinans and galactans were recovered by ethanol precipitation while demethylesterified PFs were recovered and purified by precipitation with dilute HCl. CONCLUSION: Steam treatment of CPW provides for rapid, efficient fragmentation of protopectin into highly methylesterified PFs that could be recovered by precipitation. The steaming process for preparation of PFs is environmentally friendly. No toxic chemicals are introduced and the remaining CPW can be used in fermentations to produce ethanol and other compounds. © 2012 Society of Chemical Industry 相似文献
994.
Nevin Yagci Emine Ubay Cokgor Nazik Artan Clifford Randall Derin Orhon 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(3):295-303
This paper primarily evaluates the effect of external substrate type on the composition of polyhydroxyalkanoates in enhanced biological phosphorus removal (EBPR). Two sets of sequencing batch reactors (SBRs) are operated for this purpose, one with acetate and the other with propionate as the sole carbon source at different influent COD/phosphate ratios in the range 6.7–20 mgCOD mg?1P. Results indicate that propionate is a more efficient substrate for EBPR, enabling total phosphate removal regardless of the change in COD/phosphate ratio. Total polyhydroxyalkanoates formation of 267–291 mgCOD L?1 with a slight increase at higher influent phosphorus levels is observed for acetate experiments, and a slightly lower level of 250–280 mgCOD L?1, with a similar trend for propionate experiments. The volatile fatty acid type and composition in the influent induces a significant difference in the polyhydroxyalkanoates composition of the two sets of activated sludge sustained in corresponding SBR systems. Propionate is mostly stored as 3‐hydroxy‐2‐methylvalerate and polyhydroxyvalerate, while acetate is stored as polyhydroxybutyrate. The P uptake rate in SBRs fed with propionate is considerably higher than that in the acetate reactors. Parallel batch experiments yield different results, especially for systems fed with acetate, indicating that the enzymatic system to metabolize propionate is not rapidly established, always yielding a dominant polyhydroxybutyrate fraction in the generated polyhydroxyalkanoates regardless of the level of propionate in the feed. Copyright © 2007 Society of Chemical Industry 相似文献
995.
Randall G. Gillies Jason Schaan Robert J. Sumner Melissa J. McKibben Clifton A. Shook 《加拿大化工杂志》2000,78(4):704-708
In this contribution both new and previously published deposition velocity data for aqueous Newtonian slurries are incorporated in a correlation which complements the earlier predictions of Durand, Wilson and A.D. Thomas. Most of the new data has been obtained for slurries of narrowly sized sand particles of median diameter ranging between 90 and 420 μm, in pipes of diameter between 0.05 and 0.5 m. The data were obtained in laboratory investigations under isothermal flow conditions. 相似文献
996.
The well‐known two‐layer model for predicting friction losses for pipeline flows of settling slurries has been extended to solids concentrations above 35% by volume. This has been achieved by incorporating new experimental results to account for increases in friction which have been observed with “settling” slurries at high concentrations. The kinetic (fluid‐like) friction appears to increase with solids concentration in a manner which suggests that particle‐wall contact plays an important role. The experiments also suggest that the fraction of the total solids which contributes Coulombic (velocity insensitive) friction also increases to some extent at high concentrations. This effect is expressed in a tentative correlation which employs a slurry Reynolds number. In addition, new experimental measurements of delivered and in‐situ concentrations have been used to test predictions made with the previous version of the model. The measurements show that the interracial friction factor proposed recently by Wilson and coworkers is preferable for slurries of coarse particles. 相似文献
997.
Piched Anuragudom Jad El‐daye Pawilai Chinwangso Rigoberto C Advincula Sukon Phanichphant T Randall Lee 《Polymer International》2011,60(4):660-665
A new conjugated light‐emitting AB copolymer containing alternating fluorene and naphthalene units, poly{(9,9‐di‐n‐octylfluorenediyl vinylene)‐alt‐[1,5‐(2,6‐dioctyloxy)naphthalene vinylene]} (PFV‐alt‐PNV), was synthesized via Horner‐Emmons polymerization. The polymer is completely soluble in common organic solvents and exhibits good thermal stability up to 400 °C. UV‐visible, fluorescence and photoluminescence measurements of the copolymer show peak maxima at 427, 500 and 526 nm, respectively. A light‐emitting device containing the new polymer was fabricated using a simple indium tin oxide configuration: (ITO)/PEDOT:PSS/PFV‐alt‐PNV/Al. Measurements of current versus electric field were carried out, with an onset of light emission occurring at 2.5 V. The electroluminescence brightness was observed to reach a maximum of 5000 cd m?2. Copyright © 2011 Society of Chemical Industry 相似文献
998.
Rhoads DD Wolcott RD Sun Y Dowd SE 《International journal of molecular sciences》2012,13(3):2535-2550
Clinical diagnostics of chronic polymicrobial infections, such as those found in chronic wounds, represent a diagnostic challenge for both culture and molecular methods. In the current retrospective study, the results of aerobic bacterial cultures and culture-free bacterial identification using DNA analyses were compared. A total of 168 chronic wounds were studied. The majority of bacteria identified with culture testing were also identified with molecular testing, but the majority of bacteria identified with the molecular testing were not identified with culture testing. Seventeen (17) different bacterial taxa were identified with culture, and 338 different bacterial taxa were identified with molecular testing. This study demonstrates the increased sensitivity that molecular microbial identification can have over culture methodologies, and previous studies suggest that molecular bacterial identification can improve the clinical outcomes of patients with chronic wounds. 相似文献
999.
Emmanuel Boakye Randall S. Hay M. Dennis Petry 《Journal of the American Ceramic Society》1999,82(9):2321-2331
Seven different aqueous or ethanolic precursors were used to continuously coat monazite (LaPO4 ) on Nextel 720™ fiber tows. Immiscible liquid displacement was used to minimize bridging of coating between filaments. Precursor viscosities, densities, and concentrations were measured, and solids were characterized by DTA/TGA and X-ray. Coatings were cured in-line at 1200°-1400°C and characterized for thickness, microstructure, and composition by optical microscopy, SEM, and TEM. Tensile strengths of the coated fibers varied with the precursor used and were 25% to >50% lower than those of the as-received fiber. The coating stoichiometry and coating thickness of a particular precursor did not correlate with tensile strength. Median coating thicknesses were typically ∼50–100 nm for precursors with 40–80 g/L monazite, much larger than thicknesses predicted by theory for 12 mm diameter monofilaments. There were significant thickness variations from filament to filament, but usually little variation in composition or microstructure. Amorphous AlPO4 layers formed from phosphate-rich precursors. Factors that could affect coating characteristics and tensile strength reduction were discussed. 相似文献
1000.