Effects of phenylenediamines and alkoxysilanes on gas transport properties of polyimide - silica hybrid membranes

Gas transport properties of polyimides (PIs) and their silica hybrids were investigated. The PIs synthesized with several methyl-substituted phenylenediamines were hybridized with silica via a sol–gel process with different alkoxysilanes. The prepared hybrid membranes showed controlled gas permselectivity, depending on the selected phenylenediamines and alkoxysilanes. It was worth noting that the hybrids prepared with tetraethoxysilane possessed improved CO₂ permselectivity with increasing silica content, which tended to exceed the upper-bound trade-off line. This fact suggested the additional formation of free volume holes especially favorable for the CO₂/CH₄ separation around the polymer/silica interfacial area.     

Measurement of Young’s Modulus and Poisson’s Ratio of Thermal Barrier Coating Based on Bending of Three-Layered Plate

Thermal barrier coatings (TBCs) are used to protect the hot sections of gas turbine engines and airplane engines. A TBC system comprises a substrate, bond coat, and TBC topcoat. The development of an accurate method for determining the Young’s modulus and Poisson’s ratio of TBC using a multilayered specimen is of importance. In this study, we applied the bending theory of a laminated plate to a three-layered material and proposed models to determine the Young’s modulus and Poisson’s ratio of the TBC layer using the bending strain of the TBC system specimen. Three methods were developed by utilizing (i) the coating biaxial strain, (ii) substrate biaxial strain, or (iii) coating and substrate biaxial strains. Subsequently, we determined appropriate dimensions of the specimen and span by using three-dimensional finite element analysis, and numerically verified the usefulness of the three proposed methods. However, the Young’s modulus and Poisson’s ratio determined using the multilayered specimen with a substrate are sensitive to experimental errors. Therefore, we evaluated the sensitivity of the three proposed methods to experimental error, and we determined the most insensitive method among them. Finally, we experimentally demonstrated the usefulness of this method.     

Simulation of the fracture behavior of Zircaloy-4 cladding under reactivity-initiated accident conditions with a damage mechanics model combined with fuel performance codes FEMAXI-7 and RANNS

A continuum damage mechanics model using FEM calculations was proposed to be applied to an analysis of the fuel failure due to pellet cladding mechanical interaction (PCMI) under reactivity-initiated accident conditions. The model expressed ductile fracture via two processes: damage nucleation related to void nucleation and damage evolution related to void growth and linkage. The boundary conditions for the simulations were input from the fuel performance codes FEMAXI-7 and RANNS. The simulation made reasonable predictions for the cladding hoop strain at failure and reproduced the typical fracture behavior of the fuel cladding under the PCMI loading, characterized by a ductile shear zone in the inner region of the cladding wall. It was shown that occurrence of a through-wall crack is determined at an early stage of crack propagation, and the rest of the through-wall penetration process is achieved with a negligible increment in strain. The effect of a local temperature rise in the cladding inner region on the failure strain was found to be less than 5% for the conditions investigated. Failure strains predicted under a plane strain loading were smaller by 20%–30% than those predicted under equibiaxial tensions between the hoop and the axial directions.     

Acceptor recognition of kojibiose phosphorylase from Thermoanaerobacter brockii: syntheses of glycosyl glycerol and myo-inositol

The glucosyl transfer reaction of kojibiose phosphorylase (KP; EC 2.4.1.230) was examined using glycerol or myo-inositol as an acceptor. In the case of glycerol, KP produced two main transfer products: saccharides A and B. The structure of saccharide A was O-alpha-D-glucopyranosyl-(1-->1)-glycerol and that of saccharide B was O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)-glycerol. These results show that KP transferred a glucose residue to the hydroxyl group at position 1 of glycerol. On the other hand, when myo-inositol was used as an acceptor, KP produced four transfer products: saccharides 1-4. The structures of saccharides 1 and 2 were O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively; those of saccharides 3 and 4 were O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively. KP transferred a glucose residue to the hydroxyl group at position 1 or 5 of myo-inositol. On the basis of the structures of their glucosyl transfer products, glycerol and myo-inositol were found to have a common structure with three hydroxyl groups corresponding to the hydroxyl group of the glucose molecule at positions 2, 3 and 4. The conformation of these three hydroxyl groups in the structure is equatorial. This structure is the substrate recognition site of KP. It has been suggested that KP strictly recognizes the structures of glycerol and myo-inositol, and catalyzes the transfer reaction of a glucose residue to the hydroxyl group at position 1 in glycerol, and at position 1 or 5 in myo-inositol, corresponding to position 2 in glucose.     

Optimal production-inventory policy for make-to-order versus make-to-stock based on the M/Er/1 queuing model

This paper analyzes a multi-product production / inventory system where demands for each item arrive according to a Poisson process and the production time for each product has an Erlang distribution. The paper proposes an optimality condition that specifies whether each product should be produced make-to-stock or make-to-order. In the event a product should be produced make-to-stock, an approach for computing the optimal base-stock level is proposed. Numerical examples are given for illustrative purpose.     

Mechanochemical block copolymerization in heterogeneous systems of the solid poly(vinyl chloride) with styrene by ultrasonic irradiation

Summary Mechanochemical block copolymerization in heterogeneous systems of the solid poly(vinyl chloride)-styrene-sodium dodecyl sulfate aqueous solutions has been studied by ultrasonic irradiation at 65 °C. The block copolymerization of styrene was initiated by free radicals produced from the poly(vinyl chloride) particles by ultrasonic waves. The initial rate of the block copolymerization Rp was given by Rp α [Styrene] [Sodium dodecyl sulfate]^1/2. Both copolymer and homopolymer were obtained. For example, when 2.506 g of the poly(vinyl chloride) particles, 24.23 g of styrene, and 54.00 g of sodium dodecyl sulfate aqueous solution (0.500 wt%) were added in the reaction system, the weight proportions of the block copolymer and polystyrene after 60 min were approximately 50 and 20%.     

Poly(4-diphenylaminostyrene) with a well-defined polymer chain structure: Controllable optical and electrical properties

The effect of polymer chain structure on the optical and electrical properties are reported for poly(4-diphenylaminostyrene) (PDAS), which was prepared by the living anionic polymerization of 4-diphenylaminostyrene (DAS) with the benzyllithium (BzLi)/N,N,N′,N′-tetramethylethylenediamine (TMEDA) system. The optical properties of PDAS are strongly affected by the stereoregularity of the PDAS polymer chain; intramolecular excimer-forming fluorescence was observed from PDAS with a syndiotactic-rich configuration. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PDAS were approximately −5.4 and −2.0 eV, respectively, regardless of the polymer chain structure. The hole and electron drift mobilities for PDAS were in the order of 10⁻⁴ to 10⁻⁵ (cm²/V s) and 10⁻⁵ (cm²/V s), respectively, with negative slopes. The distance of each triphenylamino (TPA) group in the polymer chain was a major factor influencing the drift mobility of PDAS. The current-voltage (I-V) characteristics of PDAS were controllable according to the polymer chain structure of PDAS.     

Process Intensification of Living Cationic Polymerization of Isobutylene by a Flow Reaction System

Increasing the reaction temperature of the living cationic polymerization of isobutylene is crucial for industrial production due to the cost of refrigeration. The reaction temperature increase was achieved with an accelerated reaction rate using a flow reaction system. The polymerization conditions, including the flow reactor design, were based on the results of kinetic studies. Utilizing a milli‐scale flow reactor, polyisobutylene, which has a narrow molecular weight distribution, was obtained within a considerably short residence time at a high temperature. Furthermore, it was confirmed that the value of M_w/M_n correlates with the product of the Reynolds number and the angle of collision.     

Spray Pyrolysis of Fe3O4–BaTiO3 Composite Particles

Fe₃O₄–BaTiO₃ composite particles were successfully prepared by ultrasonic spray pyrolysis. A mixture of iron(III) nitrate, barium acetate and titanium tetrachloride aqueous solution were atomized into the mist, and the mist was dried and pyrolyzed in N₂ (90%) and H₂ (10%) atmosphere. Fe₃O₄–BaTiO₃ composite particle was obtained between 900° and 950°C while the coexistence of FeO was detected at 1000°C. Transmission electron microscope observation revealed that the composite particle is consisted of nanocrystalline having primary particle size of 35 nm. Lattice parameter of the Fe₃O₄–BaTiO₃ nanocomposite particle was 0.8404 nm that is larger than that of pure Fe₃O₄. Coercivity of the nanocomposite particle (390 Oe) was much larger than that of pure Fe₃O₄ (140 Oe). These results suggest that slight diffusion of Ba into Fe₃O₄ occurred.