Synthesis of poly(lactic acid)‐based polyurethanes

Poly(lactic acid) (PLA) is a biodegradable aliphatic polyester, but its brittleness makes it unsuitable for many packaging and appliance applications. The goal of the work reported was to create novel poly(ester urethane)s that incorporate biodegradable poly(lactic acid) diols (PLA‐OHs) and good mechanical properties of increased molecular weight via crosslinked network formation for engineering plastics applications. Three kinds of polyols (PLA‐OHs, PLA‐OHs/poly(tetramethylene ether) glycol or PLA‐OHs/poly(butylene adipate) glycol (PBA)) and two kinds of diisocyanates (4,4‐diphenylmethane diisocyanate (MDI) or toluene 2,4‐diisocyanate (TDI)) were chosen for the soft and hard segments to compare their mechanical properties. In addition, 1,4‐butanediol and trimethylolpropane were each used as chain extender agents. Results showed the PLA/PBA‐polyurethanes (PLA/PBA‐PUs) of the MDI series and the PLA/PBA‐PUs of the TDI series had improved thermal stability and enhanced mechanical properties. Degradation behavior showed the PLA‐based polyurethanes could be degraded in phosphate‐buffered saline solution and enzyme solution. © 2012 Society of Chemical Industry     

Thermophoresis of Liquid Airborne Particles in Gravity at Continuum Regime

An analytical study is presented for the thermophoretic motion of an aerosol droplet in a prescribed temperature gradient under the influence of gravity. The Peclet and Reynolds numbers are assumed small, so that the temperature distributions are governed by the Laplace equation and the flow fields are governed by the Stokes equation. The temperature discontinuity, thermal creep, and hydrodynamic slip features that occurred at the droplet surface are considered. The slow motion of a liquid aerosol sphere subject to the combination of thermophoresis and sedimentation is obtained by superposition of the individual solutions for pure thermophoresis and pure body-force-driven motion, since both the governing equations and boundary conditions in this problem are linear. The stream functions of the internal and external flows, which are displayed in both the laboratory frame and a reference frame moving with the droplet, as well as the migrating velocity of a droplet, are formulated generally. The flow structures manifest more remarkable topologies than do those of common intuition developed from sedimentation. Our results can be simplified to the corresponding motion for solid aerosol particles.     

Mass Spectrometry of the Lithium Adducts of Diacylglycerols Containing Hydroxy FA in Castor Oil and Two Normal FA

Castor oil can be used in industry. The molecular species of triacylglycerols containing hydroxy fatty acids (FA) in castor oil have been identified. We report here the identification of twelve diacylglycerols (DAG) containing hydroxy FA in castor oil using positive ion electrospray ionization mass spectrometry of the lithium adducts. They were RR (diricinolein, R is ricinoleate), RL, RS, R‐diOH18:0, R‐diOH18:1, R‐diOH18:2, R‐triOH18:0, R‐triOH18:1, R‐triOH18:2, diOH18:0‐diOH18:1, diOH18:1‐diOH18:1 and diOH18:1‐diOH18:2. The MS² fragment ions, [M + Li ? FA]⁺ and [FA + Li]⁺, from the lithium adducts of DAG containing hydroxy FA (one or two hydroxy FA), were used for the identification. The additional fragment ions from the neutral losses of FA lithium salts [M + Li ? FALi]⁺ were used for the identification of eleven DAG containing two normal FA in a soybean oil bioconversion product. The MS² fragment ions from the neutral losses of FA lithium salts [M + Li ? FALi]⁺ were not detected from the DAG containing hydroxy FA. The DAG containing FA with more hydroxyl groups than the other FA on the same DAG molecule tended to have a prominent fragment ion [FA + Li]⁺ and an undetectable fragment ion [M + Li ? FA]⁺ while the FA was the more hydroxylated FA. Also the less hydroxylated FA of a DAG tended to have a prominent fragment ion [M + Li ? FA]⁺ and an undetectable fragment ion [FA + Li]⁺ while the FA was the less hydroxylated FA.     

Monooxygenase system of <Emphasis Type="Italic">Bacillus megaterium</Emphasis> ALA2: Studies on palmitic acid oxidation products

We identified many novel oxygenated FA produced from linoleic acid by microbial strain ALA2: 12,13,17-trihydroxy-9(Z)-octadecenoic acid (12,13,17-THOA); 12,13,16-trihydroxy-9(Z)-octadecenoic acid (12,13,16-THOA); 12-hydroxy-13,16-epoxy-9(Z)-octadecenoic acid; and 12,17;13,17-diepoxy-16-hydroxy-9(Z)-octadecenoic acid. 12,13,17-THOA, the main product, inhibits the growth of some plant pathogenic fungi. Recently, we reclassified strain ALA2 as Bacillus megaterium ALA2 NRRL B-21660 and opened a possible link with the well-studied catalytically self-sufficient P450 monooxygenase of Bacillus megaterium ATCC 14581 (NRRL B-3712) and B. subtilis strain 168 (NRRL B-4219). Now we have found that strain ALA2 also oxidizes palmitic acid into three oxygenated products: 13-, 14-, and 15-hydroxy palmitic acids. This indicates that strain ALA2 also possesses a monooxygenase system similar to the abovementioned well-known strains. These data facilitate studies on the oxygenase system of strain ALA2.     

Synthesis and properties of phosphorus containing advanced epoxy resins

A series of advanced epoxy resins with various epoxy equivalent weights were synthesized from a reactive phosphorus‐containing diol, 2‐(6‐oxido‐6H‐dibenz[c,e][1,2]oxaphosphorin‐6‐yl)‐1,4‐dihydroxy phenylene and diglycidyl ether of bisphenol A and then cured with 4,4′‐diaminodiphenyl sulfone, phenol novolac, or dicyandiamide. The parameters of the polymerization reaction (such as reaction time, catalyst) are discussed in this article. Thermal properties of cured epoxy resins were studied using differential scanning calorimetry, dynamic mechanical analysis, and thermal gravimetric analysis. The flame retardancy of cured epoxy resins was tested by limiting oxygen index. The relations between thermal properties, flame retardancy, and epoxy equivalent weights were also studied. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 429–436, 2000     

Nickel Oxide Based Supported Catalysts for the In-situ Reactions of Methanation and Desulfurization in the Removal of Sour Gases from Simulated Natural Gas

Supported nickel oxide based catalysts were prepared by wetness impregnation method for the in-situ reactions of H₂S desulfurization and CO₂ methanation from ambient temperature up to 300 °C. Fe/Co/Ni (10:30:60)–Al₂O₃ and Pr/Co/Ni (5:35:60)–Al₂O₃ catalysts were revealed as the most potential catalysts, which yielded 2.9% and 6.1% of CH₄ at reaction temperature of 300 °C, respectively. From XPS, Ni₂O₃ and Fe₃O₄ were suggested as the surface active components on the Fe/Co/Ni (10:30:60)–Al₂O₃ catalyst, while Ni₂O₃ and Co₃O₄ on the Pr/Co/Ni (5:35:60)–Al₂O₃ catalyst.     

New fluorous bipyridine ligands for copper‐catalyzed atom transfer radical polymerization of methyl methacrylate in the thermomorphic mode

The atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) is often carried out under homogeneous conditions, so the residual metal catalyst in the polymer often influences the quality of the polymer and causes environmental pollution in the long run. Novel CuBr/4,4′‐bis(R_fCH₂OCH₂)‐2,2′‐bpy complexes (R_f = n‐C₉F₁₉, n‐C₁₀F₂₁, or n‐C₁₁F₂₃; 2,2′‐bpy = 2,2′‐bipyridine) are insoluble in toluene at room temperature yet readily dissolve in toluene at elevated temperatures to form homogeneous phases for use as catalysts in the ATRP reaction, and the Cu complexes precipitate again upon cooling. The CuBr/4,4′‐bis(n‐C₉F₁₉CH₂OCH₂)‐2,2′‐bpy system produced the best results (e.g., polydispersity index by gel permeation chromatography = 1.26–1.41), in that the residual Cu content in the polymer was as low as 19.3 ppm when the ATRP of MMA was carried out in the thermomorphic mode. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

不同结构硫化钼催化剂上酚类模型化合物的加氢脱氧

Several MoS2 catalysts of different structure, prepared by in situ decomposition of ammonium heptamolybdate （AHM） and molybdenum naphthenate （MoNaph）, and by MoS2 exfoliation （TDM）, were characterized by BET, X-ray diffraction （XRD）, Energy Dispersive X-ray （EDX） and transmission electron microscopy （TEM）. The analysis showed that MoS2 structure was dependant upon the preparation procedure. The activity of the catalysts was determined by measuring the hydrodeoxygenation （HDO） of phenol, 4-methylphenol and 4-methoxyphenol using a batch autoclave reactor operated at 2.8 MPa of hydrogen and temperatures ranging from 320-370℃. By comparing the conversion, the reactivity order of the catalysts was： AHM〉TDM-D〉MoNaph〉thermal〉MoS2 powder〉 TDM-W. Also, the effect of reaction temperature on the HDO conversion was explained in terms of equilibrium of reversible reaction kinetics. The main products of the HDO for phenolic compounds were identified by gas chromatography/mass spectrometry （GC/MS）. The results showed that the product distribution and the HDO selectivity were correlated with the reaction temperature. Two parallel reaction routes, direct hydrogenolysis and combined hydrogenation-hydrogenolysis, were confirmed by the analysis of the product distribution. High temperature favored hydrogenolysis over hydrogenation for HDO of phenol and 4-methoxyphenol, whereas for 4-methylphenol the reverse was true.     

Corrosion behavior of Cr/Cu-coated Mg alloy (AZ91D) in 0.1 M H2SO4 with different concentrations of NaCl

An electroplating process was proposed for obtaining a protective Cr/Cu deposit on the two-phase Mg alloy AZ91D. The corrosion behavior of Cu-covered and Cr/Cu-covered AZ91D specimens was studied electrochemically in 0.1 M H₂SO₄ with different NaCl concentrations. Experimental results showed that the corrosion resistance of an AZ91D specimen improved significantly after Cr/Cu electrodeposition. The corrosion resistance of Cr/Cu-covered AZ91D decreased with increasing NaCl concentration in 0.1 M H₂SO₄ solution. After immersion in a 0.1 M H₂SO₄ with a NaCl-content above 3.5 wt.%, the surface of Cr/Cu-covered AZ91D suffered a few blisters. Cracks through the Cr deposit provided active pathways for corrosion of the Cu and the AZ91D substrate. Formation of blisters on the Cr/Cu-covered AZ91D surface was confirmed based on the results of an open-circuit potential test, which detected an obvious potential drop from noble to active potentials.