Effects of polar groups of polymer matrix on reinforcement-matrix interaction in kevlar fiber-reinforced composites

In order to investigate the interaction between the polar groups of reinforcement and matrix in polymer composite, mechanical properties were studied for the Kevlar fiber-reinforced composites (Kevlar is a registered trademark of E. I. duPont de Nemours Co. Inc.), in which the kind and fraction of polar components in matrix were varied using blended polymers. For the composites comprised of polymethyl methacrylate and poly(hydroxypropyl ether of bisphenol A) as the matrix, a subtransition, which can be ascribed to the interphase formed on the reinforcement surface by a strong interaction between reinforcement and matrix, appears at a temperature above the primary transition on the E″ versus temperature curves. Such a subtransition is obscured or diminished accompanying the decrease in fraction of the polar components in the matrix. The fiber efficiency factors for strength are also decreased with a decrease in the fraction of the polar components. These results imply that the reinforcement-matrix interaction is affected depending on the fraction of the polar components in matrix. For the composite comprised of blending the two polar components as the matrix, each component can contribute to the interaction with the reinforcement. The results obtained from the Fourier transform infrared spectroscopy on the matrix polymer-coated Kevlar cloth do not contradict those obtained by studying the mechanical properties.     

Residual Stress in Siliceous Glass Between Mullite Crystals

A birefringence of siliceous glass, which is coexisting with mullite crystals, was studied by an optical polarizing microscope. The cause of the birefringence was assumed to be the residual stress induced by a large contraction difference between the mullite and glass on cooling. The stress has been evaluated to be as high as—0.3 GPa, and to correspond to the elastic one which began to develop at the glass transition point.     

Tuple calculus: Formal definition and conversion from first-order calculus

In classical database theory, relational calculus has long been used in expressing query formulae and integrity constraints. In fact, relational calculus formulae are much easier to deal with than first-order formulae when evaluating queries and validating database updates in the database environment. In deductive databases, however, first-order calculus is preferred because it is convenient when proof procedures are involved. Since both situations should coexist in advanced information systems, it is very desirable to devise a conversion procedure between relational calculus and first-order calculus. In this paper, interpretation of first-order formulae in the database environment is discussed first, then tuple calculus, an extension of relational calculus, is presented. This extension enables us to describe query formulae and general rules necessary in advanced information systems, in particular, dealing with complex objects. Finally, a conversion algorithm from first-order formulae into tuple calculus formulae is presented. Several application issues are also included.     

A quantum chemical study on the polycondensation reaction of polyesters: The mechanism of catalysis in the polycondensation reaction

We carried out a theoretical study on the mechanism of catalysis in the poly(ethylene terephthalate) (PET) polycondensation reaction. Transesterification reaction of diethylterephthalate with ethanol is investigated as a model system by using the B3LYP level of theory, and Sb(OEt)₃, Ge(OEt)₄ and Ti(OEt)₄ are adopted as model catalysts. We found that the metal center of metal alkoxides coordinates to the carbonyl oxygen atom of the ester, and the alkoxy oxygen atom of alkoxy ligands attacks to the carbonyl carbon atom of the ester to form the four-centered transition state. The activation energy for tetraethoxy titanium catalyzed reaction in vacuo is 15.47 kcal/mol; this is comparable to the experimental result of 11.2 kcal/mol for poly(butylene terephthalate)/Ti(OBu)₄. Because the other mechanisms gave much higher activation energies, this is the most convincing mechanism of PET polycondensation catalysis by antimony, germanium and titanium alkoxides.     

Shear-induced pre-crystallization structures of long chain branched polypropylene under steady shear flow near the melting temperature

Shear-induced crystallization of a long chain hyper-branched polypropylene (LCB-PP, denoted PP-3) was carried out at a relatively high temperature of 170 °C, close to its melting temperature of 158 °C. Small-angle X-ray scattering (SAXS) showed that the intensity ratio of the normal to the perpendicular to the shear (V/H) was always larger than 1 for PP-3, indicating that shish-like structures were predominately formed and further growth to kebab was suppressed in PP-3. The crystallization behavior of PP-3 can be explained by the nature of PP-3 that there were a large amount of crystallization nuclei due to their branching points, and the point-like precursors formed from these nuclei were arrayed linearly along the shear direction and transformed into thread-like precursors or premature shishs; however, owing to the large amount of branching, further progress in crystallization was suppressed.     

Polar-Polar Interaction and Boundary Phase Structure Between Reinforcement and Matrix in a Polymer Composite

This paper describes an attempt to correlate the nature of polar-polar interaction between the reinforcement and matrix in a polymer composite with the boundary phase structure formed in contact with the reinforcement. It is shown by analyzing the mechanical dispersion data that the reinforcement-matrix interaction of Kevlar fiber reinforced poly(hydroxypropyl ether of bisphenol A) (P) is increased by blending poly(ethylene oxide) (E) or poly(ethylene adipate) (A) as a part of matrix, and that E is more efficient than A for the increase of the interaction. These results can be supported at the molecular level from the inspection of the Fourier transform infrared spectra on the Kevlar fiber coated with matrix polymers and the mixture of matrix polymers with benzanilide, which is used as a model compound of Kevlar fiber. It can be shown from the electron spectroscopy for chemical analysis on the films of PIE and P/A blend polymers formed on nylon 6 substrate (N), which is also used as a model material for the reinforcement, that A concentrates on the N-facing side for P/A film and that E concentrates on the air-facing side for PIE film. This result indicates the different susceptibility between P/A and PIE blends to the surface force from N, and hence, it likewise indicates the different interaction with the reinforcement in each blend, as shown by the mechanical dispersion data.     

Characterization and activity of copper-on-carbon catalysts for low-temperature selective reduction of nitric oxide with ammonia

The activities for NO reduction with ammonia in the presence and absence of O₂ have been examined over copper salts supported on activated carbon (AC) and carbon black (CB) which have been characterized by application of X-ray diffraction and scanning electron microscopy before and after use in the reduction process. The beneficial effects of increases in loading and the introduction of oxygen are demonstrated. On the most active catalyst and under optimum conditions 100% reduction of the NO to N₂ occurs at 180 °C and Cu, Cu₂O and CuO on the catalyst are shown to be present at various stages of the preparation and reduction process with large crystallites of metallic copper detected on the AC catalyst of optimum loading. Deactivation and regeneration of the catalysts is also examined. A mechanism for the redox process is proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of high performance Raney Cu-based catalysts for methanol synthesis from CO2 and H2

Catalytic hydrogenation of CO₂ into methanol has been investigated over Raney Cu-based catalysts. The Raney catalysts leached in NaOH/ZnO solutions showed high activities and selectivities for methanol synthesis. The deposition of Zn on the surface of Cu particles increased the surface area and the specific activity of Raney Cu–M. Raney Cu–Zr developed was significantly more active than a commercial catalyst.     

Risk assessment of airborne fine particles and nanoparticles

Pulmonary health effects of fine particles and nanoparticles are overviewed in this paper, mainly based on the researches conducting in our laboratory. For the hazard assessment, we exposed rats to aerosolized asbestos-substitutes or nanoparticles aerosols (nickel oxide and titanium dioxide), and examined the biological and pathological effects of the particle on lung, a major target organ for the particles, and cytokines which are related to inflammation, fibrosis and carcinogenesis in the lung. It is essential to perform comprehensive evaluation of the toxicity of poorly soluble powder samples using the precise characterization data and exposure methods, such as single instillation or aerosol inhalation.     

Organic LED full-color passive-matrix display

Abstract— A full-color 5.2-inch 1/4-VGA passive-matrix organic LED display has been developed, adopting selective deposition for the different emitting materials. The display features 320 (×3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm, white peak luminance of over 150 cd/m², and power consumption of 6 W.