Thermal stability of “living” polymer–lithium systems

The thermal stabilities of polybutadienyllithium, polyisoprenyllithium, and polystyryllithium solutions have been determined in hydrocarbon solvents. Kinetic analysis indicated that a complex mechanism was involved in the thermolysis of polybutadienyllithium. The thermal stability was observed to increase with increasing lithium concentration, suggesting the presence of competitive reactions in addition to the expected elimination of lithium hydride. The thermal stability of the three systems studied was consistent with their reported degrees of association: dimeric polystyryllithium was less stable than tetrameric polyisoprenyllithium or hexameric polybutadienyllithium.     

Properties and structure of PVP–lignin “blend films”

Blend films of poly (4‐vinylpyridine) and lignin were prepared by the casting method. Their structure and properties were studied by Fourier transform infrared (FTIR), wide‐angle X‐ray diffraction (WXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). The IR spectra of the blend films indicated that hydrogen‐bonding interaction occurred between poly (4‐vinylpyridine) and lignin. The glass transition temperature of these blends increased with the increase of lignin content, which indicated that these blends were able to form a miscible phase due to the formation of intermolecular hydrogen bonding between the hydroxyl of lignin and the pyridine ring of poly (4‐vinylpyridine). The thermostability of these blends decreased with the increase of lignin content. Initially, an appreciable increase in the measured tensile strength was achieved with a lignin content of 15%, at which the maximum value of 33.03 MPa tensile strength was reached. At a 10% lignin incorporation level, the blend film exhibited a maximum value of 9.03% strain. When the threshold in lignin content for blend films exceeded that limit of 10% lignin, the strain behavior of these blend films deteriorated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1405–1411, 2005     

On the so-called “semi-ionic” C–F bond character in fluorine–GIC

The short-range structures of fluorine–graphite intercalation compounds with stage-1 structures, C_xF (x = 2.47, 2.84, 3.61), were analyzed by means of neutron diffraction. It has been shown that the so-called “semi-ionic” C–F bond character in C_xF is essentially covalent with the bond length of 0.140 nm, and the original planar graphene sheets are buckled at the sp³-hybridized carbon atoms bound to fluorine atoms. Conjugated C–C double bonds with the bond length of 0.142 nm are preserved between the carbon atoms unbound to fluorine atoms in C_xF, while other C–C bonds are single bonds with the bond lengths of 0.153 nm. The C–F bond order in C_xF is slightly lower than those in poly(carbon monofluoride) ((CF)_n) and poly(dicarbon monofluoride) ((C₂F)_n), which is explained by the hyperconjugation involving the C–C bonds on the carbon sheets and C–F bond.     

“Swedish Base Bleed” – increasing the range of artillery projectiles through base flow

The following article summarizes the development of the base flow technique in Sweden. Extensive theoretical and experimental studies have been made in cooperation between the Research Institute of National Defence (FOA) and the Swedish Naval Materiel Department (FMV-M). Base Bleed gives a significant increase in range and reduces the dispersion. The increase in range is obviously depending on the volume made available for the unit. At firing tests an increase in range of 25% has been achieved due to the base flow effect.     

Phase Equilibrium Studies of “Cu2O”–SiO2–Al2O3 System in Equilibrium with Metallic Copper

Phase equilibria of the “Cu₂O”–Al₂O₃–SiO₂ system have been experimentally investigated at metallic copper saturation. High‐temperature equilibration, rapid quenching, and electron probe X‐ray microanalysis (EPMA) techniques have been used. Containerless equilibration technique has been developed to enable the phase equilibrium of this chemically reactive system to be investigated. The microstructures and compositions of all phases present in the quenched sample were measured accurately using EPMA. The isothermals between 1150°C and 1300°C have been determined in the “Cu₂O”–Al₂O₃–SiO₂ system at metallic copper saturation. The following primary phase fields were identified in the system: SiO₂ (tridymite), Cu₂O (cuprite), Cu₂O^.Al₂O₃ (delafossite), Al₂O₃ (corundum), and 3Al₂O₃·2SiO₂ (mullite). The implications of the phase diagram on making of the copper aluminosilicate glass have been demonstrated.     

Antioxidative Wirksamkeit von Tocochromanolen – Rangfolgebestimmung mit „Response Surface Methodology (RSM)”︁

Antioxidative Efficiency of Tocochromanols – Determination of the Sequence with ?Response Surface Methodology RSM)”? By a model study four tocopherols: α-T, β-T, γ-T and δ-T as well as the ex latice Heveae brasiliensis isolated three tocotrienols-(T₃): α-T₃, γ-T₃, and δ-T₃ were investigated on their antioxidative efficiencies to protect linoleic acid methyl ester. With fixed temperatures and appointed oxygen supply resulted from repeated measurements the values of the standard deviations of the dates. For each of the seven tocochromanols by using Response Surface Methodology as statistical Method a regression equation was formulated and further by multiple regression analysis evaluated and at last by 3-D-response surface graphically represented. So it is possible to present synoptically all the area of experience known by the variable conditions of the several experiments. A ranking of the tocochromanols depends on the choosen conditions for temperature and oxygen. Only δ-T was even effective by a residual amount of 25% in spite of the extreme condition of 80°C/20% O₂ within 6 hours.     

Efficient, “one-pot” synthesis of suspension crosslinked sulfonated polystyrene via a Friedel–Crafts reaction

A suspension technique leading to macronet ionic resins is described based on a single reactor process. The procedures demonstrate sulfuric acid as a polar suspending medium that can act as a sulfonating agent, a Friedel–Crafts catalyst, and a crosslinking agent. The sulfonation reaction was finally completed using sulfuric acid excess, or oleum 65%. High yields were obtained for the crosslinking and the sulfonation reaction, while the final products were characterized by using ion-exchange capacity measurements, U.V. spectra, and determination of the degree of crosslinking. The number average molecular weight between crosslinks and the ion-exchange capacity H⁺→Na⁺ of the resins was decreasing by increasing the nominal crosslinking ratio. © 1992 John Wiley & Sons, Inc.     

Development of a Continuous Segmented Flow Tubular Reactor and the “Scale‐out” Concept – In Search of Perfect Powders

The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production.     

The “cold‐solutioning” phenomenon in cellulose triacetate–acetone mixtures

Direct mixing of cellulose triacetate (CTA) in acetone at room temperature produces only an opaque swollen gel at all concentrations. However, cycling the mixture between room temperature and ?78 ± 3°C results in a stable solution at room temperature, if the concentration is less than 6% (w/w). This process has been called “cold‐solutioning.” Such a process also produces a clear solution at concentrations between 6% (w/w) and 10% (w/w); however, in time, the solution separates slowly into at least two phases, a clear liquid and an opaque gel phase. At concentrations above 10% (w/w) and below 20% (w/w), the system exhibits two phases. A completely opaque swollen gel forms at concentrations of 20% (w/w) and above. The above‐described cold‐solutioning phenomena are shown to be the coupled kinetic and thermodynamic consequences of (1) the large thermal stresses that would result from thawing a swollen mixture of CTA and acetone, arising from the large differences in their thermal expansion coefficients; and (2) the “bimodal” composition of the cellulose derivative. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1697–1707, 2003     

Solvent extraction — the challenges of a “mature” technology

The solvent extraction area is perceived by some chemical engineers as being mature and fully developed. The present review shows that this is not the case. Many chemical engineering problems must be solved before equipment can be confidently designed from first principles. The review also outlines progress in extraction process chemistry, and in new techniques such as membrane extraction.