Preparation and solubility of water–methanol mixtures in sulfonated poly(etherketone) containing a cardo‐ring structure

The preparation and solubility of water–methanol mixtures in sulfonated (1,3‐dihydro‐3‐oxoisobenzofuran‐1,1‐diyl‐1,4‐phenyleneoxy‐1,4‐phenylenecarbonyl‐1,4‐phenyleneoxy‐1,4‐phenylene) (C‐PEK) was systematically studied. The sulfonation was carried out by reacting C‐PEK with 98% sulfuric acid at 60°C. This reaction obeys a first‐order reaction mechanism up to 4 h. The sulfonic acid group was uniformly dispersed in a sulfonated C‐PEK (SC‐PEK) membrane. The introduction of sulfonic acid groups in C‐PEK could increase polymer segmental gaps because of the size of a bulky sulfonic acid group or decrease polymer segmental gaps as a result of polar interactions. The former effect is dominant for SC‐PEK with low sulfonic acid content, whereas the latter occurs for SC‐PEK with high sulfonic acid content. The uptake of pure water or an aqueous methanol solution (e.g., 3, 5, and 10 wt % methanol concentration) in the sulfonated C‐PEK membranes increases with increasing sulfonic acid group content. However, the sulfonated C‐PEK with high sulfonic acid content selectively sorbs water rather than methanol in the membrane. This suggests that the sulfonated C‐PEK membrane could prevent crossover of methanol through the membrane and has potential as a polymer electrolyte for the direct methanol fuel cell. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1113–1123, 2006     

Investigation of aluminum particle combustion in the flame of solid rocket propellants

Aluminum is widely used in modern solid rocket propellants for many purposes, but mainly to increase the specific impulse by raising the flame temperature. Most of the aluminum present in the powder state in the propellant does not vaporize on the burning surface, tending later to agglomerate into large particles difficult to burn even in the flame. The aim of this work is to study the behavior of the aluminum particles on the burning surface and in the gaseous region of the propellant flame structure. Different diagnostic techniques have been used: SEM on the burning surface of extinguished samples, pictures taken during combustion by filtered still camera, and a newly developed laser diagnostic. By the use of an UV laser beam and a high-speed-shutter TV camera, the Al particles on the burning surface have been visualized. A suitable image processor to extract information from the frames has been adopted. Tests on an HTPB. 12/AP.68/Al.20 propellant in the pressure range 10–50 atm have been performed. Results show the reliability of the diagnostics used here and have contributed to a better characterization of the tested propellant.Published in Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 115–119, May–June, 1993.     

Impact damage behaviour of CVD-coated silicon nitride for gas turbines

Impact tests were conducted on the silicon nitride substrates coated with Si₃N₄ and SiC by chemical vapour deposition (CVD). For both 100- and 200-m-thick Si₃N₄-coated silicon nitride, Hertzian crack extension was reduced by debonding at the interface. Although Hertzian crack extension was not reduced for 100-m-thick SiC-coated silicon nitride, it was reduced for 200-m-thick SiC-coated silicon nitride. Theoretical calculations suggest that debonding at the interface consumed the fracture energy of Hertzian crack extension in the case of Si₃N₄ coatings, but it was observed that Hertzian cracks were not arrested at the interface.     

Product design for strong cover glass

Strength is one of the most important properties of cover glass. In this study, fracture analysis is used to classify the breakage mode of cover glass into four typical modes. Moreover, the mechanism and evaluation method of each mode are investigated. Consequently, a chemical strengthening design with high compressive stress (CS) and low center tension (CT) is obtained. In addition, processing design is determined to be an important factor. Fining of edge processing and surface polishing after chemical strengthening are shown to enhance the edge and surface strength, respectively.     

Syntheses of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers and their surface enrichment of their blend with acrylate adhesive copolymers

Several types of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers (PMMA‐g‐PDMS) were synthesized using macromonomer technology. Three types of PMMA‐g‐PDMS with different PDMS chain length were obtained. The effect of siloxane chain length on surface segregation of PMMA‐g‐PDMS/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate)[P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended on the PDMS chain length, significantly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1736–1740, 2002     

Facile Formation of Uniform Shell‐Crosslinked Nanoparticles with Built‐in Functionalities from N‐Hydroxysuccinimide‐Activated Amphiphilic Block Copolymers

An amphiphilic block copolymer, poly(methylacrylate)₈₂‐block‐poly(N‐(acryloyloxy)succinimide_0.29‐co‐(N‐acryloylmorpholine)_0.71)₁₅₅ (PMA₈₂‐b‐P(NAS_0.29‐co‐NAM_0.71)₁₅₅), was synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization and then was supramolecularly assembled into micelles in aqueous solution, followed by chemical crosslinking throughout the shell region upon the introduction of 2,2′‐(ethylenedioxy)‐bis(ethylamine) as a crosslinker to afford well‐defined shell crosslinked nanoparticles (SCKs). The number‐averaged hydrodynamic diameters of the micelles and SCKs were (17 ± 4) nm and (16 ± 3) nm, respectively, by dynamic light scattering (DLS), and (15 ± 2) nm and (13 ± 2) nm, respectively, by transmission electron microscopy (TEM). In an attempt to narrow the particle size distributions, the dodecyl trithiocarbonate chain end of the block copolymer was replaced by a 2‐cyanoisopropyl moiety. Each nanoparticle system was characterized by DLS, electrophoretic light scattering (ELS), TEM, and small‐angle X‐ray scattering (SAXS). SAXS was of particular importance, as it provided definitive observation and quantification of shell contraction and densification upon shell crosslinking. The direct incorporation of NAS into the block copolymers during their preparation allowed for unique crosslinking chemistry to proceed with added diamino crosslinkers. The primary advantages of this system include the ability to conduct in situ synthesis of SCKs that are crosslinked directly and derivatized easily by adding nucleophilic ligands before, during, or after the crosslinking.     

Sputter etching mechanism and changes of surface structure of PTFE

Growth of microscopic cones on PTFE surface by RF sputter etching process are studied. The surface texm changes from initial submicron hillocks to large cones during sputter etching. The height of these cones is 33 to 45 percent of the etching depth calculated from etching rate. The direction of these cones is nearly equal to the ion incident angle. Boundary energy of sputtering and growth of cones are 100 eV and 150 eV, respectively. It is obtained that the redeposition ratio by back diffusion to sputtered molecule is 11 percent from the experiment using collector. It is concluded that redeposition and repolymerization process of sputtered material occurs in parallel with the ion etching process, and cones continue to grow partly during etching.     

N-Nitrosodimethylamine Formation from Hydrazine Compounds on Ozonation

N-Nitrosodimethylamine formation from six hydrazine compounds on ozonation was investigated. N-Nitrosodimethylamine formation yields in groundwater (pH 7) were 7.5%–89%. Results in the presence of tert-butyl alcohol indicated that N-nitrosodimethylamine was formed by reaction with molecular ozone, except for tetramethyltetrazene. From the results of effects of pH, tert-butyl alcohol and water matrix (groundwater and river water), it was suggested that reactions of tetramethyltetrazene with ozone, hydroxyl radicals, etc., were associated with N-nitrosodimethylamine formation. Some reactions restricted N-nitrosodimethylamine formation. Because N-nitrosodimethylamine formation of hydraxine compounds on chloramination was low, they are more important N-nitrosodimethylamine precursors on ozonation in actual water treatment.     

Alteration of acidic lipids in human sera during the course of pregnancy: characteristic increase in the concentration of cholesterol sulfate

Using genomic DNA from late-onset retinal degenerate and wild type Labrador Retrievers as templates and canine exon-specific oligonucleotides as primers in polymerase chain reaction, all four introns of opsin were cloned and sequenced. Dot-matrix comparisons were made for human, murine and canine introns. Selected sequences containing either intronic or coding sequences were aligned and used for phylogenetic relationship analysis. The opsin gene introns are conserved between the human, the mouse and the dog with regards to number and length. In addition there is an astonishingly high degree of sequence homology between the second and fourth introns. Introns 2(1277 bp in dog) and 4 (863 bp in dog) are 72% and 71% homologous to the human introns, and 57% and 52% homologous to the mouse introns, respectively. The coding sequence (CDS) of the dog shows 93% homology to human CDS and 88% homology to mouse CDS. A phylogenetic analysis of the intronic sequences 2 and 4 confirms the higher relatedness between dog and human than between mouse and human opsin genes. As there are good reasons to believe that the primate and rodent lineages are closer to each other than to the Canis familiaris, there must be some functional constraints on the evolution of human and dog opsins.