Photorheology of Fast UV‐Curing Multifunctional Acrylates

Summary: The fast photopolymerization of different multifunctional acrylates was analyzed by means of photorheology. The materials studied included a penta/hexaacrylate monomer and two different acrylated hyperbranched polymers. The sensitivity of the commercial rheometer was improved several‐fold, by a combination of an adaptive filter algorithm and improved data treatment, using powerful oversampling acquisition hardware. The novel set‐up was capable of monitoring up to a five orders of magnitude increase in shear modulus within short experiment timescales (about 10 s). The improvement in sensitivity and acquisition rate enabled the induction time, gelation, and vitrification of the multifunctional acrylates to be determined. In addition, the influence of UV intensity on stiffness build‐up within these materials was studied. In the case of the penta/hexaacrylate system, gelation and vitrification were detected as distinct events, in contrast to the second‐generation hyperbranched polyester, for which vitrification could not be identified. These findings are related to the difference in the glass transition temperature of the cured networks.

Absolute value of the complex shear modulus as a function of time for different acrylate monomers during UV curing.     

A Symmetrical Diester as the Sex Attractant Pheromone of the North American Click Beetle Parallelostethus attenuatus (Say) (Coleoptera: Elateridae)

Hexanoic acid, 1-octanol, 1,8-octanediol, octyl hexanoate, 1,8-octanediol monohexanoate, and 1,8-octanediol dihexanoate were identified in headspace volatiles collected from the crushed abdomen of a female click beetle of the species Parallelostethus attenuatus (Say) (Elaterinae, tribe Elaterini). In field trials carried out in Illinois, South Carolina, North Carolina, and Virginia, adult male beetles were strongly attracted to 1,8-octanediol dihexanoate alone. Blends of the dihexanoate with one or more of the other compounds proved to be less attractive than the dihexanoate alone, suggesting that the pheromone of this species may consist of a single compound. The symmetrical diester structure of the pheromone is a novel natural product and appears to be structurally unique among insect pheromones.

     

Continuous production of structured phospholipids in a packed bed reactor with lipase from <Emphasis Type="Italic">Thermomyces lanuginosa</Emphasis>

The possibilities of producing structured phospholipids between soybean phospholipids and caprylic acid by lipase-catalyzed acidolysis were examined in continuous packedbed enzyme reactors. Acidolysis reactions were performed in both a solvent system and a solvent-free system with the commercially immobilized lipase from Thermomyces lanuginosa (Lipozyme TL IM) as catalyst. In the packed bed reactors, different parameters for the lipase-catalyzed acidolysis were elucidated, such as solvent ratio (solvent system), temperature, substrate ratio, residence time, water content, and operation stability. The water content was observed to be very crucial for the acidolysis reaction in packed bed reactors. If no water was added to the substrate during reactions under the solvent-free system, very low incorporation corporation of caprylic acid was observed. In both solvent and solvent-free systems, acyl incorporation was favored by a high substrate ratio between acyl donor and phospholipids, a longer residence time, and a higher reaction temperature. Under certain conditions, the incorporation of around 30% caprylic acid can be obtained in continuous operation with hexane as the solvent. Presented at the 95th American Oil Chemists' Society Annual Meeting and Expo in Cincinnati, Ohio, May 10, 2004.     

Relating catalyst structure and composition to the water–gas shift activity of Cu–Zn-based mixed-oxide catalysts

In order to investigate the effect of cerium oxide on Cu–Zn-based mixed-oxide catalysts four catalyst samples were characterized by means of XRD, in situ XANES and thermogravimetric analysis. The activity of the catalyst samples was tested for the forward water–gas shift reaction. Cerium oxide was found to increase the crystallinity of the ZnO phase indicating a segregation of the Cu and ZnO phases. The TOF of the water–gas shift reaction based on chemisorption data was found to be independent of composition and preparation conditions of the four catalyst samples. In contrast, the catalyst stability depends on composition and preparation conditions. Cerium oxide impregnated before calcination of the hydrotalcite-based Cu–Zn precursors leads to a more stable water–gas shift catalyst.     

Small-scale hydrogen production from propane

Partial oxidation and oxidative steam reforming of propane were investigated over 0.01 wt.% Rh/Al₂O₃ foam catalysts. High selectivity to hydrogen was obtained for both reactions, but addition of steam to the reactant mixture gave higher selectivity to hydrogen. Stability tests over 7 h revealed that the catalytic activity of Rh was quite stable under partial oxidation conditions. Higher loss in Rh activity was observed when steam was present in the reactant mixture. FE-SEM images showed that Rh particle size and distribution are modified under partial oxidation and oxidative steam reforming conditions. However, these changes were more distinct on the catalyst used for oxidative steam reforming.     

Biotransformation of 2-Benzoxazolinone to 2-Amino-(3<Emphasis Type="Italic">H</Emphasis>)-Phenoxazin-3-one and 2-Acetylamino-(3<Emphasis Type="Italic">H</Emphasis>)-Phenoxazin-3-one in Soil

An alternative to the use of synthetic pesticides is to exploit the natural defense chemicals produced by cereals. An important class of allelochemicals is cyclic hydroxamic acids and related benzoxazolinones. A prolonged degradation experiment of the allelochemical compound from rye 2-benzoxazolinone (BOA) was carried out for up to 90 d at 15°C at three different concentration levels, 3, 3000, and 30,000 nmol BOA· g soil^–1, respectively, in a sandy loam soil. Two main degradation products, 2-amino-(3H)-phenoxazin-3-one (APO) and 2-acetylamino-(3H)-phenoxazin-3-one (AAPO), were identified and quantified by LC-ESI-MS-MS. The half-life of BOA increased with higher levels of BOA added to the soil. Half-lives of BOA, APO, and AAPO were determined by fitting a single first-order model to the degradation data. Half-life of BOA was determined to be 0.6 d in the 3 nmol BOA g soil^–1 treatment. Half-lives of BOA, APO, and AAPO were 3.1, 2.7, and 2.1 d, respectively, in the 3000 nmol BOA· g soil^–1 treatment. In the 30,000 nmol BOA· g soil^–1 treatment, the half-lives were 31 d for BOA and 45 d for APO. The microbial community structure was not affected by addition of BOA to the soil as investigated by analysis of signature fatty acids. The results suggest that the exploitability of BOA for crop protection is dependent on the existing concentration of BOA in the soil and the timing of incorporation of hydroxamic acid synthesizing crops into the soil.     

Shear behavior of flexible polyurethane foams under uniaxial compression

The mechanisms behind the load building capabilities of a hyperbranched polymer (HBP) in polyurethane (PU) foams have been investigated, using microscopy techniques and mechanical analyses. By broadening the traditional uniaxial compression characterization of PU foams to include combined shear deformations and compression behavior, an apparent Poisson ratio of the foam could be obtained in situ. The Poisson ratio as function of uniaxial compression ratio of the foam was thus studied for foams filled with Styrene Acrylonitrile (SAN) and foams containing HBP. Generally a window of deformation ratios could be defined in which the Poisson ratio was negative. The width of this window varied systematically with the SAN loading, where an increase in SAN particle loading resulted in a broadening of the negative Poisson ratio window. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

4,4‐Dimethyl‐ and Diastereomeric 4‐Hydroxy‐4‐methyl‐ (2S)‐Glutamate Analogues Display Distinct Pharmacological Profiles at Ionotropic Glutamate Receptors and Excitatory Amino Acid Transporters

Subtype‐selective ligands are of great interest to the scientific community, as they provide a tool for investigating the function of one receptor or transporter subtype when functioning in its native environment. Several 4‐substituted (S)‐glutamate (Glu) analogues were synthesized, and altogether this approach has provided important insight into the structure–activity relationships (SAR) for ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs), as well as the excitatory amino acid transporters (EAATs). In this work, three 4,4‐disubstituted Glu analogues 1 – 3 , which are hybrid structures of important 4‐substituted Glu analogues 4 – 8 , were investigated at iGluRs and EAATs. Collectively, their pharmacological profiles add new and valuable information to the SAR for the iGluRs and EAAT1–3.     

The reaction of NiO/NiAl2O4 particles with alternating methane and oxygen

The reduction and oxidation behaviour of oxygen carrier particles of NiO and NiAl₂O₄ has been investigated in a fluidized bed reactor as well as a thermogravimetric analyzer (TGA). The particles showed high reactivity and gas yield to CO₂ with methane in the temperature interval 750–950°C. In the fluidized bed the yield to CO₂ was between 90 and 99% using bed masses corresponding to 16–57 kg/MW_fuel. Complementary experiments in a TGA at 750 and 950°C showed a clear reaction of the NiAl₂O₄ with CH₄ at the higher temperature. There was methane released from the reactor at high degrees of solid oxidation, which is likely associated with the lack of Ni‐sites on the particles which can reform the methane. There was some carbon formation during the reduction, although the amount was minor when the gas yield to carbon dioxide and degree of oxidation of the solid was high. A simple reactor model using kinetic data from a previous study predicted the gas yield during the reduction in the fluidized bed experiments with reasonable accuracy. The oxygen carrier system investigated in this work shows high promise for use in a real CLC system, provided that the particle manufacturing process can be scaled up with reasonable cost.     

Intumescent foams—A novel flame retardant system for flexible polyurethane foams

A combination of intumescent components was evaluated as a novel flame retardant system in a flexible polyurethane foam, and the incorporation of these components gave rise to a significant enhancement of the flame retardant properties of the foam. The heat release rate was lowered at an early stage as well as throughout the fire, the total heat production was decreased and the time to ignition was prolonged. Mechanical measurements of the foam revealed enhanced properties in terms of stiffness accompanied by a large decrease in elongation at break as compared with a reference foam. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008