SOLUBILITY OF CARBON DIOXIDE IN AQUEOUS AND ANHYDROUS MIXTURES OF METHYLDIETHANOLAMINE AND TRIETHYLENE GLYCOL MONOMETHYL ETHER

Mixed solvents are a combination of chemical and physical solvents and are used for the removal of acid gases from gas streams. The solubility of CO₂ in a mixed nonaqueous solution of methyldiethanolamine (MDEA) (50 wt.%) and triethylene glycol monomethj'l ether (TEGMME) (50 wt.%) has been measured at 40°C. The data are compared with solubility data of CO₂ in pure TEGMME. The solubility of CO₂ has been measured at 40°C and 100°C in an aqueous mixed solvent consisting of MDEA (40 wt.%) and TEGMME (40 wt. %) and water (20 wt.%) at partial pressures of CO₂ up to 12 MPa. The solubility results were compared with the solubility in the nonaqueous mixed solvent and previously reported data of aqueous MDEA. The solubility model of Deshmukh and Mather was used to correlate the data.     

Polyurethanes derived from caprolactone polyesters and diamines

Thermoplastic, light-stable polyurethanes have been prepared by the interfacial poly-condensation of secondary diamines with the bischloroformates of polyester diols derived from ε-caprolactones. A straight-line relationship was obtained from a logarithmic plot of inherent viscosity versus M _n. The effect of some structural variations on the properties of the polyurethanes is discussed. These variations included the molecular weight of the polyester diol, the initiator used in preparing the polyester diol, the introduction of a methyl substitutent on the caprolactone ring, and the structure of the diamine. Polyurethanes prepared from polyester diols of M _n from 2000–4000 are opaque, stiff materials which undergo a melting transition at 40–50°C. characteristic of the polyester component. Polyurethanes which are flexible and translucent at room temperature are obtained either by using a low molecular weight polyester diol or a copolyester diol containing > 25% methyl ε-caprolactone. The polyurethanes described are soluble in several common solvents and can be cold-drawn to produce material of high tensile strength. Thermal studies using DTA and TGA Show an exothermic reaction starting above 300°C. Rapid weight loss beginning at 300–330°C. and leveling off near 500°C. accounted for 85–90% of the total sample and is attributed to decomposition of the polyester Chains.     

Electrostatic effects on the thermodynamics of protonation of reduced plastocyanin

The L12E, L12K, Q88E, and Q88K variants of spinach plastocyanin have been electrochemically investigated. The effects of insertion of net charges near the metal site on the thermodynamics of protonation and detachment from the copper(I) ion of the His87 ligand have been evaluated. The mutation-induced changes in transition enthalpy cannot be explained by electrostatic considerations. The existence of enthalpy/entropy (H/S) compensation within the protein series indicates that solvent-reorganization effects control the differences in transition thermodynamics. Once these compensating contributions are factorized out, the resulting modest differences in transition enthalpies turn out to be those that can be expected on purely electrostatic grounds. Therefore, this work shows that the acid transition in cupredoxins involves a reorganization of the H-bonding network within the hydration sphere of the molecule in the proximity of the metal center that dominates the observed transition thermodynamics and masks the differences that are due to protein-based effects.     

Reduction of NO by H2 and CO on PdO-MoO3/γ-Al2O3 of low molybdena loading

The activity and selectivity in the catalytic reduction of NO by a mixture of CO and H₂ of three PdO-MoO₃/-Al₂O₃ catalysts are compared in the presence of varying amounts of oxygen at reaction temperatures from 100 to 550°C. The catalysts were prepared by different methods and contain about 2% Mo and 2% Pd. Results are compared with those for PdO/-Al₂O₃, PdO-MoO₃/-Al₂O₃ containing 2% Pd and 20% Mo, and a commercial Pt-Rh catalyst. The PdO-MoO₃/-Al₂O₃ catalysts are more active for the selective reduction of NO to N₂ and N₂O than PdO/-Al₂O₃ under slightly oxidizing conditions at temperatures from 300 to 550°C. At these reaction conditions, the fresh PdO-MoO₃/-Al₂O₃ catalysts are comparable with a commercial Pt-Rh catalyst. The improved activity of PdO-MoO₃/-Al₂O₃ relative to PdO/-Al₂O₃ is believed to be due to the interaction between Pd and Mo. The effect of O₂ on the activity and selectivity of these catalysts is different in the reduction of NO by H₂, by CO, and by a mixture of H₂ and CO. The results using the mixture of reductants cannot be inferred from the results with the single reductants.     

A thermostable variant of fructose bisphosphate aldolase constructed by directed evolution also shows increased stability in organic solvents

Thermostable variants of the Class II fructose bisphosphate aldolase have been isolated following four rounds of directed evolution using DNA shuffling of the fda genes from Escherichia coli and Edwardsiella ictaluri. Variants from all four generations of evolution have been purified and characterized. The variants show increased thermostability with no loss of catalytic function at room temperature. The temperature at which 50% of the initial enzyme activity is lost after incubation for 10 min (T50) of the most stable variant, 4-43D6, is increased by 11-12 degrees C over the wild-type enzymes and the half-life of activity at 53 degrees C is increased approximately 190-fold. In addition, variant 4-43D6 shows increased stability to treatment with organic solvents. DNA sequencing of the evolved variants has identified the mutations which have been introduced and which lead to increased thermostability, and the role of the mutations introduced is discussed.     

Development of cracks in injection moldings of poly (2,6-dimethyl-1, 4 phenylene ether)

Cracks in injection molded articles adversely affect their appearance as well as their ultimate properties. In this study, we have investigated the spontaneous development of cracks in samples molded from an engineering plastic in the absence of external loading. The specimens of a well characterized poly(2,6-dimethyl-1,4 phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The initiation and development of cracks in the molded articles were monitored for a period of eighty weeks. The presence and the frequency of the cracks were found to depend on the operating conditions employed during the molding, the shape of the cavity, the presence of Irregularities at the mold surface, and the particular location observed. The results were elucidated under the light of the results of microstructural analyses including residual stress and birefringence distributions on both compression and injection molded specimens of the engineering plastic.     

Mass transfer and radical flux effects in dispersed‐phase polymerization of isooctyl acrylate

The kinetics of dispersed phase polymerization of a highly water‐insoluble monomer (isooctyl acrylate) were explored in emulsion, miniemulsion, and microsuspension polymerization. The effects of monomer water solubility and choice of initiator (oil‐ vs. water‐soluble) strongly impact the final product (particle size and molecular weight distribution). For emulsion polymerization, as the surfactant concentration was increased, there was a transition from homogenous to micellar nucleation near the CMC, then a drop in nucleation rate at high surfactant concentration due to insufficient radical flux to support more nucleation. For miniemulsion polymerization, a slow rate of growth of (droplet) nucleation with surfactant concentration was found, followed (at the CMC) by an increase in the rate of nucleation with added surfactant as the mode of nucleation switched to micellar. The conversion‐time kinetics of microsuspensions could be modeled with a bulk polymerization model. IOA is sufficiently insoluble in the aqueous phase that emulsion polymerization may or may not be reaction limited. The presence of a stabilizer such a PAA, the use of an oil‐soluble initiator such as BPO, and the insolubility of IOA in the aqueous phase all push the polymerization locus toward droplet (microsuspension) nucleation and bulk kinetics.© 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5649–5666, 2006     

Evaluation of the aromatic structure of coal tar pitch by solid and solution state n.m.r.

Rapid magic angle spinning has been used to obtain sideband-free high field ¹³C n.m.r. spectra of coal tar pitches in the solid state. However, the unfavourable cross-polarization and ¹H relaxation characteristics make it difficult to accurately estimate concentrations of quaternary aromatic carbon using the dipolar dephasing method. The concentrations of bridgehead aromatic carbon in the whole pitch and toluene-insoluble fraction investigated were deduced using a combination of solid and solution state n.m.r. and elemental analyses.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Trap trees for elm bark beetles

European elm bark beetles,Scolytus multistriatus (Marsh.), were strongly attracted to American elms,Ulmus americana L., baited with theS. multistriatus attractant, multilure, or killed by injection of the arboricide, cacodylic acid; a combination of the two treatments was most attractive. Comparisons of beetle catches on sticky bands affixed to the trees with samples of bark from the same trees showed that the number of beetles landing on cacodylic acid-treated trees was approximately 40 times greater than the number boring into them. Spraying the bark with the insecticide chlorpyrifos had no direct effect on attraction. No live bark beetle brood was found in trees that had been treated with cacodylic acid or chlorpyrifos, but trees that were only baited or left untreated (check) were attacked, killed, and colonized. We suggest that the contribution of the cacodylic acid trap tree technique to Dutch elm disease control will be enhanced by baiting treated trees with multilure and spraying their lower boles with 0.5% chlorpyrifos. This treatment will eliminate diseased and unwanted elms as potential breeding material and kill large numbers of elm bark beetles that might otherwise innoculate healthy elms with the Dutch elm disease fungus.