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  • Polymer and Materials Science  (52)
  • Life Sciences
  • Meteorology and Climatology
  • 1990-1994  (23)
  • 1975-1979  (31)
  • 1
    Electronic Resource
    Electronic Resource
    Conformations and time-resolved fluorescence of oligomers of (-)-epicatechin with 4β → 8 interflavan bonds (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 537-545 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligomers of (-)-epicatechin with 4β → 8 interflavan bonds, and as many as five monomer units, have been studied by conformational analysis and time-resolved fluorescence. The conformational analysis yields 2x-1 conformations for each oligomer with x monomer units. There are two conformations accessible at each interflavan bond. These conformations are denoted by + and -. The dominant conformations for the trimer and higher oligomers have an interaction between the phenolic hydroxyl groups on monomers i and i+2. This interaction involves the hydroxyl group at C(5) on monomer i, and either C(13) or C(8) of monomer i+2, depending on whether the conformation of the two intervening interflavan bonds is + + or + -, respectively. Minor contributions to the ensemble for the tetramer and pentamer are made by conformations that contain the sequence of successive interflavan bonds denoted by -+ or --. In -+ the interaction between monomer units i and i + 2 involves an aliphatic hydroxyl with a phenolic hydroxyl, and there are no hydroxyl-hydroxyl interactions between units iand i + 2 in --. The onset of a different decay law for the fluorescence when x increases from 3 to 4 may be associated with the appearance of the -+ and -- conformations as minor constituents in the ensemble.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310509
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  • 2
    Electronic Resource
    Electronic Resource
    Irregularities in steady flow for non-newtonian fluids between cone and plate (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 953-965 
    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: Flow irregularities have been visually observed in solutions of polyacrylamide of high molecular weight on shear in a cone-and-plate rheometry (gap angle 2.3°). This anomalous flow was found to depend on molecular weight, concentration, and solvent. The onset of flow irregularities were generally at shear rates 〈 5 sec-1. A dimensional analysis shows that the elastic component of the fluid is responsible for the anomalous flow. The onset of flow irregularities has been predicted from measurements of recoverable strain as a function of shear stress.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230401
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  • 3
    Electronic Resource
    Electronic Resource
    The preparation and tensile properties of polyethylene composites (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 3249-3265 
    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: Single polymer composites have been prepared using different morphologies of polyethylene as matrix and as the reinforcement. Depending on annealing conditions, the ultraoriented fibers used as reinforcement can have higher melting points (ca. 139°C) than the matrix made from the same conventionally crystallized high-density polyethylene (ca. 132°C) or from low-density polyethylene (ca. 110°C). The optimum temperature has been assessed for bonding to occur by growth of transcrystalline regions from the melt matrix without considerable modulus reduction of the annealed ultraoriented and reinforcement fiber or film. Pullout tests have been used for determining the interfacial shear strength of these single polymer composites. The interfacial shear strength for the high-density polyethylene films embedded in a low-density polyethylene matrix is 7.5 MPa and for high-density polyethylene self-composites is 17 MPa. These values are greater than the strength for glass-reinforced resins. The strength is mainly due to the unique epitaxial bonding which gives greater adhesion than the compressive and radial stresses arising from the differential shrinkage of matrix and reinforcement. The tensile modulus of composites prepared from uniaxial and continuous high-density polyethylene films embedded in low-density polyethylene obeys the simple law of mixtures and the reinforced low-density polyethylene modulus is increased by a factor of 10. High strength cross-ply high-density-polyethylene - low-density-polyethylene laminates have also been prepared and the mechanical properties have been studied as the film orientation is varied with respect to the tensile axis.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1978.070221119
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  • 4
    Electronic Resource
    Electronic Resource
    Anisotropy of the fluorescence from the monomer, five oligomers, and a polymer of epicatechin (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 57-60 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The steady-state fluorescence anisotropy r has been measured at 25°C for dilute solutions of epicatechin units connected by interflavan bonds with 4β → 8 stereochemistry. The molecules studied are monodisperse oligomers from the monomer through the hexamer, and a polydisperse sample with a number-average degree of polymerization xn of 10. The hexamer and smaller oligomers have been removed from the polydisperse sample. All samples have a very small value of r in 1,4-dioxane and in methanol. Higher values of r are seen in ethylene glycol and in glycerol. In the latter two solvents, the monomer has significantly higher r than any species with xn 〉 1. This observation is interpreted as evidence for the presence of excitation migration from one monomer to another in the dimer and species of higher xn.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290109
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  • 5
    Electronic Resource
    Electronic Resource
    On the melting behavior of a thermotropic rigid random copolyester based on terephthalic acid and substituted hydroquinones (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1891-1902 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermotropic liquid crystalline random copolyesters, based on terephthalic acid and substituted hydroquinones, display an unusually large heat for the crystal-nematic transition; this phenomenon is related to their highly ordered structures. To modify the structures, annealing was carried out in the solid state at different temperatures over different times. As the annealing time or temperature is increased, the melting peaks shift to higher temperatures, whereas the heat of fusion shows no significant change or is lowered, respectively. An explanation is offered in terms of crystal perfection and a molecular weight increase. No evidence for a random-to-block conversion on annealing is found.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281102
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  • 6
    Electronic Resource
    Electronic Resource
    Planar deformation of amorphous poly(ethylene terephthalate) by stretching and forging (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 687-691 
    Details
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate), amorphous, planar deformation of ; deformation of PET by stretching and forging ; drawing techniques and deformation of PET ; crystallization in drawn PET ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The planar deformation of amorphous poly(ethylene terephthalate) (PET) was performed by stretching and by forging under comparable conditions at a series of constant temperatures, 80, 90, 100, and 110°C. The highest planar draw ratios of 4.5 × 4.5 and 3.5 × 3.5 were obtained by forging and stretching, respectively. Samples were studied before and after deformation by wide angle x-ray scattering (WAXS), differential scanning calorimetry (DSC), density measurements, and elastic recovery at 100°C. A distinct difference in efficiency of draw between these two techniques is found, as judged mainly by the straininduced crystallization. The forging is more effective than stretching in achieving stabilized planar draw under comparable process conditions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090300705
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  • 7
    Electronic Resource
    Electronic Resource
    Miscible blends of modified poly(aryl ether ketones) with aromatic polyimides (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 821-830 
    Details
    ISSN: 0887-6266
    Keywords: blends of modified PEEK with aromatic polyimides ; miscibility of blends of modified PEEK with aromatic polyimides ; Spectra, IR and UV, of blends of modified PEEK with aromatic polyimides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and the n-phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310710
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  • 8
    Electronic Resource
    Electronic Resource
    Melting behavior of poly(ether ether ketone) in its blends with poly(ether imide) (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1845-1850 
    Details
    ISSN: 0887-6266
    Keywords: melting behavior of PEEK/PEI blends ; equilibrium melting point ; crystal reorganization ; interlamellar segregation ; melting point depression ; interaction parameter ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We detail the melting behavior of poly(ether ether ketone) (PEEK) and investigate its melting behavior in miscible blends with poly(ether imide) (PEI). The determination of the equilibrium melting point (Tm0) of PEEK is discussed by considering its inhomogeneous morphology. Tm0 is obtained by a long extrapolation of a Hoffman-Weeks plot to 384°C. Hindrance of PEEK crystal reorganization induced by PEI during heating is observed over the blend composition investigated (20-75 wt % PEEK). This behavior is correlated with the incorporation of PEI in the interlamellar zones of PEEK crystals. The interaction parameter χ of PEEK/PEI blends is estimated by the equilibrium melting point depression. This gives the interaction density B = -1.2 cal/cm3, and x = -0.40 at 400°C. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311217
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  • 9
    Electronic Resource
    Electronic Resource
    Viscoelastic properties of linear chain macromolecular gels. Growth of stress at the onset of steady shear flow (1979)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 76 (1979), S. 191-208 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Anwachsen von Zugspannung und Scherung zu Beginn einer konstanten Scherung wurde an Lösungen linearer Makromoleküle untersucht, um Aussagen über nichtlineare Viskoelastizität zu machen. Die Polyacrylamide (PAAm)…wurden in Wasser, Formamid und Ethylenglycol gelöst. Die Polymeren wurden in diesem Labor hergestellt. Sie waren unverzweight und initiatorfrei. Die Polystyrolproben (PS) von der Pressure Chemical Company wurden in Dekalinlösung untersucht. PAAm zeigt mit steigendem Molekulargewicht und steigender Konzetration zunehmend typischen Gelcharaketer in allen drei Lösungsmitteln. für homogene Systeme wurde Gelbruch und ein „undershoot“ beob-achtet. Zum ersten Ma1 konnten „overshoot“ aufgrund von verhakten Ketten und auf-grund von energetisch assoziierten Ketten voneinander unterschieden werden. Dies Ver-halten zeigt einen grol3en Gegensatz gegenuber dem PS/Dekalin-System und zeigt die Starke der Nebenvalenzbindungen in den PAAm-Systemen.
    Notes: The growth of stress (shear stress and normal stress) at the onset of steady shear flow was investigated for linear chain macromolecular fluids to determine nonlinear viscoelasticity. The polyacrylamides (PAAm) were dissolved in H2O, formamide and ethyleneglycol. The polymers were prepared in this laboratory. They were unbranched and free of initiator. The polystyrene (PS) samples from Pressure Chemical Company were studied in decalin solutions. PAAm shows increasingly typical gel character - in all 3 solvents - with increasing molecular weight and polymer concentration. For homogeneous systems gel fracture and undershoot were observed. Further for the first time overshoot due to entangled molecules and overshoot due to energetically associated chains have been distinguished. This behaviour is a strong contrast to the PS/decalin system and demonstrates the strength of the second valence bondings in the PAAm-systems.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1979.050760111
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  • 10
    Electronic Resource
    Electronic Resource
    A new approach for processing ultrahigh-molecular weight polyethylene powder: Solid-state rolling followed by hot stretch (roll-draw) (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 2441-2444 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281220
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