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  • Chemistry  (17)
  • Cell & Developmental Biology
  • 1995-1999  (3)
  • 1985-1989  (14)
  • 1965-1969
  • 1995  (3)
  • 1988  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Melt transcrystallization of polyethylene on high modulus polyethylene fibers (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 35 (1988), S. 1945-1953 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A polytheylene composite was prepared and tested. It was consisted of a high-density polyethylene (HDPE) matrix and uniaxial gel-spun high-modulus PE fiber. Aided by the similarity between matrix and fiber, transcrystallization of HDPE melt on the PE fiber surface was generated. Nucleating agents were not employed. The transcrystalline growth of HDPE on the PE fiber surface was found to consist of an inner and an outer zone. The inner zone, 2-3 μm thick, is composed of HDPE crystals nucleated on the PE fiber surface. Photomicrographs showed a well-defined region of row-nucleated HDPE on the surface of PE fiber. This means the fibrils of HDPE were found to grow out from the PE fiber axis and HDPE crystallites are oriented in planes perpendicular to the PE fiber axis. The fiber in the composite induced the transcrystalline growth of HDPE on the PE fiber surface at higher temperature than on cooling the melt. For 36 wt% fiber, the increase was 2.5°C, also resulting in ∼ 10% more crystals. Crystallization of a composite with 50 wt% fiber at 124°C involved two steps: The first a fast transcrystallization of HDPE on the PE fiber surface followed by the bulk crystallization of the HDPE.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070350720
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of glutathione conjugates by fast atom bombardment/tandem mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 615-621 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment (FAB) of glutathione conjugates, has been studied by tandem mass spectrometry (MS/MS) using hybrid sector/quadrupole instruments. Abundant fragments of diagnostic utility were present in the daughter ion spectra. Common fragmentation modes were observed but their relative importance was strongly dependent on the nature of the conjugated species. As an example of a general approach to the characterization of glutathione conjugates in biological samples, the acetaminophen-glutathione conjugate was identified in rat bile, following coadministration of (2H0)- and (2H3)acetaminophen, using the experimental sequence: (i) conventional FAB mass spectrometric analysis, (ii) MS/MS using constant neutral loss (129 u) scanning to identify parent ions corresponding to glutathione conjugates, (iii) MS/MS to yield daughter ion spectra of parents so identified and corresponding to (2H0)- and (2H3)-labeled conjugates.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200151107
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  • 3
    Electronic Resource
    Electronic Resource
    Reproducibility in capillary supercritical fluid chromatography: Comparison of injection techniques (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 29-32 
    Details
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography ; Injection techniques ; Reproducibility ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the precision obtained using commercially available microvalve injectors is reported for three modes of injection: conventional split; timed-split; and direct. Results from this study show that good precision (〈 3% RSD for external standard and 〈 1% RSD for internal standard methods) can be obtained with capillary supercritical fluid chromatography (SFC). However, particular attention must be paid to the type of valve used, the orientation of the column relative to the valve, the mode of interfacing or connecting the column to the valve, and the type of pressure or density programming used for the analysis as all of these factors will affect the reproducibility.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110109
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  • 4
    Electronic Resource
    Electronic Resource
    A deformation induced order-disorder transition in isotactic polypropylene (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 842-851 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this study, isotactic polypropylene (i-PP) has been deformed by uniaxial compression to draw ratios up to 16×, and at draw temperatures from 30°C to 140°C. An order-disorder transition in the crystals is observed at draw temperatures well above the stability limit, 70°C, reported for the disordered phase; Furthermore, this disordered phase (called smectic) is found to induce ductility and improve the efficiency of draw. The deformation induced smectic phase has been characterized using WAXS, DSC, and on-line compression load versus draw ratio measurements. In consequence, a set of process conditions are offered to optimize draw. A mechanism for plastic deformation of i-PP is also suggested, using the smectic phase as a probe.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760281304
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  • 5
    Electronic Resource
    Electronic Resource
    Deformation of semicrystalline polymers via crystal-crystal phase transition (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1049-1057 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A classification is given of flexible, semicrystalline polymers based on the early stage deformation behavior in the solid state. The criteria of each category are discussed with experimental evidence from the literature on 17 polymers. The central aim of this classification is to point out the possibility of ductility induced during deformation. The understanding of the induced ductility in a given semicrystalline polymer suggests a systematic route to optimize solid-state deformation processes for achieving high draw ratios.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260509
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  • 6
    Electronic Resource
    Electronic Resource
    Uniaxial drawing of poly(ethyleneoxide)/poly(methyl methacrylate) blends by solid-state extrusion (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 2499-2508 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultradrawn ribbons of solution-cast blends of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) have been prepared by a solid-state coextrusion in a capillary rheometer. An increase of noncrystallizable PMMA in the blends drastically decreased the drawability from a draw ratio of 36 for pure PEO to 5 for a mixture of PEO/PMMA 40/60% by weight. A low crystallinity and depression of melting temperature for PEO were observed with increasing draw. The Flory-Huggins theory for melting temperature depression has been used to derive the binary interaction parameter for these blends.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090261208
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  • 7
    Electronic Resource
    Electronic Resource
    A latent entanglement model for the draw of semicrystalline polymers (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 813-819 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel molecular model, the latent entanglement, is proposed to explain the relationships between ductilities of polyethylene reactor powders and different conditions of synthesis. According to Hoffman's variable cluster model, irregularities in the crystallite fold surface increase as the synthesis temperature is decreased. The concept of latent entanglement stems from the potentiality of these defects to convert into active entanglements when the involved chain segments are drawn out of the crystals.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030161106
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  • 8
    Electronic Resource
    Electronic Resource
    Depression of the crystal-nematic phase transition in thermotropic liquid crystal copolyesters (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 83-90 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal-nematic phase transition of a copolyester consisting of 20 mol% poly(ethylene terephthalate) and 80 mol% p-hydroxybenzoic acid (PHB) was characterized by depression of the crystal-nematic transition by the addition of a liquid crystal diluent. This copolyester contains blocks of crystalline PHB. Its transition behavior was compared with thatrandom copolyester with diluent of the same composition. From the extrapolated transition temperature depression data, the heat of transition per mole of p-oxybenzoate was calculated as about 1.3 kcal/mol, with an entropy of about 2 cal/deg mol. This assumes that only the p-oxybenzoate unit crystallized from the nematic state. The validity of the Flory-Huggins model for this transition point depression was confirmed graphically by comparison with two different thermotropic-liquid crystal polyesters. These results may represent the first reported crystal-nematic temperatures and heats generated by the dilution method for liquid crystal copolyesters of this type.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260104
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular interactions in polystyrene cosolvent systems (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 981-988 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Studied here are miscible binary cosolvents for polystyrene, for which polystyrene is insoluble in either of the individual solvents. Polymer-solvent interactions in solutions of atactic polystyrene in acetone/diethyl ether and in methylcyclopentane (MCP)/acetone binary cosolvents have been investigated using nuclear magnetic resonance (NMR) spectroscopy. Polystyrene 13C chemical shifts were measured as a function of miscible binary solvent compositions and temperature. The NMR data were used to calculate “association constants” as a measure of specific interactions of the solvent components with all sites on the polymer. In mixtures of acetone and diethyl ether, 13C-NMR indicates a weak interaction between the polystyrene phenyl ring and the diethylether solvent component. In the polystyrene/MCP/acetone system, present NMR data reveal no preferential interactions. Additional NMR measurements were performed on polystyrene in mixtures of CCl4/acetone. From these results, it is concluded that although preferential polymer-solvent interactions are present in some cosolvent systems, they are not a prerequisite for such behavior.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260503
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  • 10
    Electronic Resource
    Electronic Resource
    Uniaxial Draw Of Poly(aryl-ether-ether-ketone) by solid-state extrusion (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 795-805 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(aryl-ether-ether-ketone) (PEEK) films and rods have been solid-state extruded at 154 and 310°C, respectively. The crystal orientation functions, melting behavior, density, and tensile properties of the drawn PEEK films (EDR ≤ 3.7) and rods (EDR ≤ 5.5) have been measured. As extrusion draw ratio (EDR) was increased, the c-axis orientation function, melting temperature, and tensile modulus and strength increased. Moduli up to 6.5 GPa and the strengths up to 600 MPa, 3 and 6 times the values of undrawn films, respectively, were obtained for the drawn films. The thermal expansivities along (α‖) and perpendicular (α⊥) to the draw direction of PEEK rods were measured from -40 to +10°C. As EDR was increased, α⊥ increased, but α‖ decreased. At EDRs of 3.8 and 5.5, α‖ even exhibited negative values (about -5 × 10-6°C-1), probably due to reversible contraction of elongated tie-molecules.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260406
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