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  • Articles: DFG German National Licenses  (6)
  • Chemical Engineering  (4)
  • EXAFS  (2)
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  • Articles: DFG German National Licenses  (6)
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Years
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    EXAFS and XANES studies of Zn2+ and Rb+ neutralized perfluorinated ionomers (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 734-746 
    Details
    ISSN: 1435-1536
    Keywords: Microstructure ; nafion ; ionomer ; EXAFS ; XANES
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) experiments have been carried out to probe the Zn2+ and Rb+ environment in perfluorinated ionomers. The cation environment has been determined for these ionomers in their dry, hydrated and n-amyl alcohol swollen state. It was found that a well ordered, crystalline-like nearest-neighbor oxygen shell predominates in the zinc neutralized perfluorinated ionomers. Unlike the zinc ionomers, the Rb+ neutralized ionomers show no discernible peaks in the radial structure function indicating that the rubidium environment is highly disordered. Coordination of the hydroxyl groups of namyl alcohol to cations was suggested by EXAFS analysis. XANES analysis was useful in corroborating the EXAFS information and in providing information about the ionic character of the nearest-neighbor bonding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451546
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Blends of metal acetates and polyurethanes containing pyridine groups II. SAXS and EXAFS studies (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2357-2366 
    Details
    ISSN: 0887-6266
    Keywords: metal acetates ; polyurethanes ; pyridine units ; blending ; SAXS ; EXAFS ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyurethanes containing pendant pyridine units were blended with various metal acetates and studied by small-angle x-ray scattering (SAXS) and extended x-ray absorption fine structure spectroscopy (EXAFS) to better understand the microscopic effect of blending on these materials. An earlier investigation found a dramatic enhancement in mechanical properties after blending, which suggests at least two pyridine units were coordinating to a single cation. This coordination would enable the cation to act as a cross-linking site, which could then cause the observed changes in mechanical properties. To determine the effect of complexation on the microphase-separated domain structure, small-angle x-ray scattering patterns were collected. Neutralization with a metal acetate increased the scattered intensity, which can be explained by an increase in electron density contrast but may also have been due to an improvement in phase separation. The distance between lamellar domains was basically unaffected by the addition of metal acetate, with the exception of nickel acetate. In this instance the distance decreased, which was caused by an improvement of packing inside the hard segments. EXAFS at the nickel and zinc edges indicated that the same qualitative changes occurred in the local environments around both cations after blending versus the unblended acetates. The magnitude of the first shell peak in the radial structure function (RSF) increased significantly upon blending, a result that is difficult to rationalize. The higher shell peaks exhibited significant changes in position and magnitude upon blending, which indicates substantial local rearrangement around the metal cation These fundamental changes in the EXAFS spectra may have been due to complexation between the cation and the pyridine group, but the results were not conclusive. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321406
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of radiation curable polyurethanes containing pendant acrylate groups (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1442-1450 
    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: A series of radiation sensitive and relatively high molecular weight poly(tetramethylene adipate) polyurethanes containing pendant acryfate functionality was synthesized. These radiation curable materials possess good mechanical properties and behave like common thermoplastic elastomers prior to chemical crosslinking which further enhances their strength and insolublizes them. Both the precursor and the cured materials were characterized by stress-strain, differential scanning calorimetry. and dynamic mechanical testing. It was found that the poly-(tetramethylene adipate) soft segments with molecular weight of 2000 or higher were crystallizable in the cross-linked network. The soft segment molecular weight and the diisocyanate type were found to be important in determining the tensile and thermal properties of these male-rials. The crosslinking process was found to depress crystallization of the soft segments and to improve tensile properties. Increasing the soft segment molecular weight resulted in an Increased elongation al break bill a decreased ultimate stress for both the precursor linear polymers and the crosslinked materials.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760262014
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Differential scanning calorimetry analysis of morphological changes in segmented elastomers (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 190-197 
    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: Investigations of morphological changes which are induced in segmented elastomers by annealing and quenching are reported. Four different polymers were studied each based on the same soft segment - 1000 or 2000 molecular weight poly(tetramethylene oxide). The hard segments were 4,4′-diphenylmethane diisocyanate (MDI) chain extended with 1,4-butane diol (ET series), piperazine coupled with 1,4-butane diol bischloroformate (BN-1,4), or dimethyl terephthalate condensed with 1,4-butane diol (H-50). Following annealing at various temperatures (120, 150, 170, or 190°C), the polymers were quenched to ambient conditions, and their properties measured by differential scanning calorimetry (DSC) as a function of time following the quench. DSC measurements taken immediately after the quench show that the soft segment Tg is higher than that of the control, suggesting that the applied thermal history promoted increased mixing of hard and soft segments. As time passes after quenching, the Tg values decrease and approach an equilibrium value. This effect is much smaller for those samples having crystalline hard segments. Endotherms attributed to the disruption of long range ordering in the hard segment domains resulted from the annealing process. These endotherms appeared at higher temperatures for higher annealing temperatures. The positions of crystalline melting endotherms were independent of the annealing/quenching conditions investigated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760200304
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanical and optical properties of block polymers I. Polyester-urethanes (1969)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 383-387 
    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: The extraordinary physical properties exhibited by block polymers have been ascribed to the presence of a multiphase microstructure in which the higher modulus phase acts as a quasi-crosslink or filler particle. Recently, the optical examination of these materials combined with mechanical testing has given investigatiors new insight into this complex morphology. In this investigation, simultaneous stress, strain, and birefringence data have been collected on a block polyester urethane elastomer. Stress-softening is observed in cyclic stress-strain experiments, giving rise to significant hysteresis in the stressstrain and birefringence-stress curves. In these tests, prestrain causes a large increase in the stress-optical coefficient, but has little effect on the strain-optical coeffcient. As the temperature is increased, the strain-optical coefficent decreases while the stress-optical coefficient increases with the latter exhibiting a larger temperature dependence than predicted by the kinetic theory of rubber elasticity. The good agreement between the mechanical-optical response of polyester urethanes and that of other block polymer systems provides further evidence of their morphological similarity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760090602
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Properties of polyisobutylene-polyurethane block copolymers: I. Macroglycols from ozonolysis of isobutylene-isoprene copolymer (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 337-349 
    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: The properties of a series of polyisobutylene (PIB) based polyurethanes were studied and compared to those reported in the literature for polyether, polyester, and polybutadiene-based polyurethanes. Good phase separation was reflected in the invariance of the soft segment Tn with increasing hard segment content. Increasing hard segment content resulted in larger domains, higher modulus and lower ultimate elongation. The modulus above the soft segment Tn was higher than that previously reported for polyurethanes of similar hard segment contant; improved phase separation and short contour lengths of the PIB chains were cited as possible causes of this behavior. Stress-strain data indicated a change from isolated to interconnected domain morphology with incerasing hard segment contant. Generally similar trends were seen for all types of urethanes. The overall properties of polybutadiene polyurethanes were closest to those of the polyisobutylene polyurethanes studied. The properties of both of these systems were suggested to suffer from significant synthesis problems in urethane formation due to the incompatibility of the nonpolar hydrocarbon soft segment and the polar diol chain extender. Preliminary environmental tests indicated that polyisobutylene based materials exhibit improved hydrolytic stability and reduced moisture permeability compared to polyether and polyester polyurethanes and greater oxidative stability compared to polybutadiene based materials.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760230608
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    Paper (German National Licenses)
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