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  • Polymer and Materials Science  (17)
  • FLUID MECHANICS
  • 1995-1999  (8)
  • 1975-1979  (9)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 1973-1985 
    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: Comparisons were made of differential scanning-calorimetric (DSC) thermograms of both liquid and powdered commercial phenol-formaldehyde resins. By a combination of the results from analyses under a variety of conditions, such as ambient pressure, high pressure, using freeze-dried samples, and also by direct observation of the resin-curing process in wood-veneer assemblies, the curing reactions of phenol-formaldehyde resins were found to differ for resol and novolac systems. At a heating rate of 10°C/min, the resol resin showed endothermic curing reactions at temperatures of about 150°C, while the novolac-type resin showed an exothermic peak maximum at about 160°C. Results are presented to show how DSC can be used to differentiate between a resol and novolac system.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 257-261 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New scaling laws for chain networks are derived to describe the fundamental relationships between the viscosity exponent (k), viscoelastic exponent (m), stretched exponent (β), spatial dimension (d). fractal dimension (df), and a universal constant (γ). The scaling of the total number of monomers and the radius of gyration is defined by df. We have discovered γ = m/β to be a universal constant which relates the shear modulus of a polymer gel melt to the shear modulus near the glass transition. Analyzing the size-dependent shear viscosity, we have determined γ = 3dfcd/(7d-5dfc) = 2.647 for d = 3 where dfc is the fractal dimension of critical clusters at the gel point. By using γ, the present theory extends previous work pertaining to systems near the sol-gel transition, and shows how properties far from the critical point can be explained. The theoretical prediction is in good agreement with viscoelastic measurements.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 1-17 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ring-opening polymerization of 2-methyl-2-oxazoline initiated by 2-(p-nitrobenzenesulfonato)ethyl methacrylate follows the so-called “living mechanism”, i.e. fast initiation compared to slow propagation and no chain transfer. Accordingly, methacryl macromonomers having homopolymers, block or random copolymers of 2-methyl and 2-pentyl-2-oxazoline backbones with narrow molecular weight distribution were obtained. Termination of the propagating species by ion-exchange or aminolysis with triethylamine yielded hydroxyl and quaternary ammonium terminated macromonomers, respectively.
    Additional Material: 12 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 397-404 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new free volume distribution function for amorphous polymers is derived on the basis of a lattice model. It provides a good description of the non-Gaussian spreading observed very recently in positron annihilation experiments. This new theory shows that the non-Gaussian distribution is a result of the large density fluctuations of holes from their equilibrium. The Gaussian distribution is recovered in the limit of small fluctuations. The size and volume distribution of the holes is uniquely defined by two structural parameters: the energy of hole formation and the lattice volume. Our theory predicts that increases in temperature will broaden the distribution and shift its lower peak to higher free volume. Increases in pressure have the opposite effect.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 1189-1201 
    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: The effect of water vapor on a polyimide has been investigated in the temperature region of -190 to 325°C using an automated torsion pendulum. A damping peak, TH2O developes at -122°C (1 Hz) in the thermomechanical spectra of the polymer which is due to water-polymer interactions. The peak intensifies as the humidity of the conditioning atmosphere, at both 30° and at 325°C, increases and attains a limiting value at about 3000 ppmv H2O. The process is reversible. It is concluded that the number of sites in the polymer for interaction with water is low and limited (〈0.3 molecule H2O per polymer repeat unit) and, assuming direct proportionality between the intensity of the loss peak and the amount of water adsorbed, that the adsorption of water vapor follows the Langmuir isotherm.
    Additional Material: 10 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 20 (1976), S. 1619-1626 
    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 dual-calibration method for the determination of molecular weights and molecular weight distribution of styrene-maleic anhydride copolymers (S/MA) by gel permeation chromatography (GPC) is introduced. It might be applicable to copolymers of other type. A linear relationship of intrinsic viscosity [η] and weight-average molecular weight (M̄w) for unfractionated S/MA in tetrahydrofuran (THF) at 25°C can be expressed by the equation \documentclass{article}\pagestyle{empty}\begin{document}$ \left[ \eta \right] = 3.98 \times 10^{ - 4} \bar M_w^{0.596} . $\end{document} The maleic anhydride content of the copolymers ranges from 5 to 50 mole-%, and the M̄w range is from 2 × 104 to 7 × 106. The plot of log [η] M̄w versus GPC elution volume of the S/MA copolymers falls on the same curve as that of the polystyrene standards in THF.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 428-432 
    ISSN: 0021-9304
    Keywords: BoneSource™ ; hydroxyapatite cement ; biomaterial ; craniofacial skeletal reconstruction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: BoneSource™-hydroxyapatite cement is a new self-setting calcium phosphate cement biomaterial. Its unique and innovative physical chemistry coupled with enhanced biocompatibility make it useful for craniofacial skeletal reconstruction. The general properties and clinical use guidelines are reviewed. The biomaterial and surgical applications offer insight into improved outcomes and potential new uses for hydroxyapatite cement systems. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 428-432, 1998
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 35 (1997), S. 273-277 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The calcium phosphate cement (CPC) used in this study was formed by combining equimolar amounts of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). This powder, when mixed with water, sets to a hard cement in about 30 min. However, the water-based CPC paste is not highly cohesive and is vulnerable to washout until hardening occurs. The objectives of this study were to investigate the effects on handling properties, washout resistance, cement hardening behavior, and mechanical properties of adding several gelling agents to CPC paste. Aqueous solutions that contained a mass fraction of 2-4% of hydroxypropyl methylcellulose (HPMC), carboxyl methyl-cellulose (CMC), chitosan acetate, and chitosan lactate were used as cement liquids. Hardening time was measured by the Gilmore needle test; resistance to washout was evaluated by the disintegration of the cement specimen in water with agitation; and mechanical strength was evaluated by the measurement of diametral tensile strength and compressive strength. Handling properties were greatly improved by the addition of HPMC, CMC, chitosan acetate, and chitosan lactate. Hardening time was retarded by the additions of HPMC and CMC, and mechanical strength was weakened by the addition of either the chitosan lactate or the chitosan acetate. © 1997 John Wiley & Sons, Inc. J. Biomed Mater Res, 35, 273-277, 1997.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 967-970 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Relations are derived for the linear and volumetric thermal expansion coefficients of a filled polymer containing aligned ellipsoidal inclusions at finite concentrations. The analysis follows a procedure recently developed for elastic moduli by application of a generalized approach of Eshelby. The well-known Kerner equation is shown to be a limiting case of the present finding. From data on glass in epoxy resin, we conclude that the volumetric expansion varies only slightly with the aspect ratio of an ellipsoid; however, the longitudinal and transverse, linear, expansions show a strong dependence on the particle shape.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1305-1310 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Very few analyses exist for determining the adhesion f thin brittle films in the micron range on low modulus polymeric substrates. A theoretical model and experimental means are developed to determine the adhesion for this situation using the concept of fracture mechanics and Griffith's energy criterion. An expression for the adhesion is derived in terms of the external loading, material constants, and thicknesses of the films.The model is compared with measurements of brittle films vacuum deposited onto polymeric substrates. Excellent agreement is obtained and interfacial energies are calculated. Since the moduli of thin films are very difficult to determine accurately, the effect of a variation in measurements of this material parameter on the adhesion is calculated. The effect of varying preparative conditions is also discussed.
    Additional Material: 4 Ill.
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