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  • Polymer and Materials Science  (8)
  • 34.50.Fa  (3)
  • linear viscoelasticity  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Mapping of the relaxation patterns of polymer melts with linear flexible molecules of uniform length (1997)
    Springer
    Rheologica acta 36 (1997), S. 330-344 
    Details
    ISSN: 1435-1528
    Keywords: Relaxation time spectrum ; monodisperse polymers ; hypergeometric function ; incomplete gamma function ; linear viscoelasticity ; polymer dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The linear viscoelastic material functions of linear flexible polymers of uniform length are calculated from the BSW spectrum (Baumgaertel et al., 1990, 1992), and explicit analytic expressions are presented for several of the most common material functions for transient and dynamic experiments. However, numerical calculations are presented whenever needed. The BSW spectrum was determined from experimental G″, G″ data of two sets of molten polymers of narrow molecular weight distribution, polystyrene and polybutadiene. The purpose of the mapping is to show a wide range of viscoelastic behavior which otherwise is not available in such comprehensive form. Experimental check of these predictions is still needed in most cases. Also, some insight into the predictions for the non-linear (including the non-equilibrium) viscoelastic behavior is achieved by studying two particular experiments: the start-up of uniaxial extension at constant rate and the start-up of shear flow at constant rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366674
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  • 2
    Electronic Resource
    Electronic Resource
    Mapping of the relaxation patterns of polymer melts with linear flexible molecules of uniform length (1997)
    Springer
    Rheologica acta 36 (1997), S. 330-344 
    Details
    ISSN: 1435-1528
    Keywords: Key words Relaxation time ; spectrum ; monodisperse polymers ; hypergeometric function ; incomplete gamma function ; linear viscoelasticity ; polymer dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The linear viscoelastic material functions of linear flexible polymers of uniform length are calculated from the BSW spectrum (Baumgaertel et al., 1990, 1992), and explicit analytic expressions are presented for several of the most common material functions for transient and dynamic experiments. However, numerical calculations are presented whenever needed. The BSW spectrum was determined from experimental G′,G″′ data of two sets of molten polymers of narrow molecular weight distribution, polystyrene and polybutadiene. The purpose of the mapping is to show a wide range of viscoelastic behavior which otherwise is not available in such comprehensive form. Experimental check of these predictions is still needed in most cases. Also, some insight into the predictions for the non-linear (including the non-equilibrium) viscoelastic behavior is achieved by studying two particular experiments: the start-up of uniaxial extension at constant rate and the start-up of shear flow at constant rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366674
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The relaxation of linear flexible polymers which are slightly poly-disperse (1996)
    Springer
    Rheologica acta 35 (1996), S. 645-655 
    Details
    ISSN: 1435-1528
    Keywords: Rheology ; polymers ; poly-dispersity ; linear viscoelasticity ; relaxation time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The relaxation of slightly poly-disperse linear flexible polymers has been expressed in a simplified blending rule which is presumed to be a weighted linear superposition of the relaxation spectra of mono-disperse components which constitute the blend. Discrete components are characterized by their molecular weight M i,weight fraction w i,and relaxation time spectrum H i(λ). ). In contrast to broadly distributed blends in which the small molecules mobilize the large ones and vice versa, we introduce the term “slightly polydisperse” for blends with molecular weight distributions narrow enough to have very little change in the longest relaxation times of each molecular weight component. The properties of this blending rule are analyzed and dynamic data is calculated for slightly poly-disperse polystyrene. As an application, the blending rule is used to determine the characteristic mono-disperse parameters (BSW parameters) of two materials, poly (vinyl methyl ether) and polycarbonate, for which we could not determine their BSW parameters directly since they were not available in nearly monodisperse form. The proposed blending rule can only be applied to systems in which all components are above the entanglement molecular weight, i.e. M i≫M c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396513
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  • 4
    Electronic Resource
    Electronic Resource
    Metallocene catalysts for olefin polymerizations. XXIV. Stereoblock propylene polymerization catalyzed by rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl)(1-η5-indenyl)dimethyltitanium: A two-state propagationSee Reference 1. (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2601-2617 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysts ; ansa-metallocene catalyst ; thermoplastic elastomeric poly(propylene) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic-anti-[ethylidene(1-η5-tetramethylcyclopentadienyl) (1-η5-indenyl)dimethyltitanium (6) has been synthesized and its molecular structure determined by x-ray diffraction methods. The two Ti=Me(1) and Ti=Me(2) units have bond distances differing by 0.08 Å and their proton NMR resonances are separated by over 1 ppm. Using this compound and methylaluminoxane (MAO) as the activator, at 25°C the 6/MAO catalyst produced polypropylene having crystalline domain with physical crosslinks. The polymers obtained at lower polymerization temperatures are rheologically liquids. The behaviors of this catalyst system resembles closely the previously reported rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl) (1-η5-indenyl)dichlorotitanium (4)/MAO system. The structure of 6 determined here furnishes tangible support for the proposed two-state (isomeric)-switching propagation mechanism. Addition of MAO to 6 causes broadening of the Me(1) resonance in the 1H-NMR spectra, and 6 is decomposed by Ph3C+B(C6F5)-4. © 1992 John Wiley & Sons, Inc.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301215
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  • 5
    Electronic Resource
    Electronic Resource
    Population of NaI-terms in grazing ion surface collisions (1990)
    Springer
    The European physical journal 17 (1990), S. 109-117 
    Details
    ISSN: 1434-6079
    Keywords: 34.50.Fa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The population of NaI 3p- and 4d-terms after grazing collisions of fast Na+-ions with a clean Al(111)-surface is studied via optical spectrometry. The ratio of level populationsN(3p)/N(4d) is investigated in dependence on projectile velocity under different experimental conditions. For clean targets and a defined geometry of detection a threshold for excitation of the 4d-term is observed. The data are described by a model of population via resonant one electron tunneling which incorporates the effects of the projectile velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437664
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and properties of an easy-processable bismaleimide thermoset resin (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 451-459 
    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: Reaction of methylenedianiline and maleic anhydride in acetone, followed by cyclodehydration in the presence of acetic anhydride and 1,4-diazabicyclo [2.2.2] octane as a catalyst, affords a mixture of compounds, Desbimid, with maleimide, isomaleimide, and acetamide groups. Dissolution of this mixture in styrene and 2-hydroxyethyl methacrylate results in clear liquid resins. The viscosity of the formulated resins ranges from 100-1700 mPas at 25°C depending on the concentration of Desbimid. These systems can be processed and cured at ambient temperatures until demoulding and postcured at temperatures up to 200 or 250°C. The flexural modulus, flexural strength, and elongation at break of a number of cured formulations are found between 3500-3800 N/mm2, 90-115 N/mm2, and 2.7-3.5%, respectively.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450310
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  • 7
    Electronic Resource
    Electronic Resource
    Recycling of sheet-molding compounds by chemical routes (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 1409-1417 
    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: This article describes a number of chemical routes for the recycling of sheet-molding compounds (SMC) consisting of glass fibers, filler (calcium carbonate), and an unsaturated polyester-styrene thermoset resin. Treatment of milled SMC with ethanol/potassium hydroxide at 85°C for 48 h ultimately affords a soluble polymeric fraction, consisting of styrene-fumaric acid copolymers. The excess of potassium hydroxide as well as the filler are removed via a neutralization step, which results in a large stream of waste chemicals. Treatment of SMC chips with ethanolamine at 180°C for 48 h gives a reaction mass that can be split into three fractions, viz., the glass fibers, the filler, and a methanol-soluble polymeric residue. The excess of ethanolamine is recovered by distillation at 220°C and reduced pressure. The polymeric fraction consists of terpolymers of styrene, N,N′-di(2-hydroxyethyl)fumaramide and N-2-hydroxyethylmaleimide monomer units, the latter two bearing two and one hydroxyl groups, respectively. The terpolymer shows little solubility in unsaturated polyester, epoxy, or isocyanate resins. The glass fibers and the filler coated with the polymeric fraction can be used as constituents of bulk-molding compounds (BMC). Replacing half of the original amount of glass fibers or filler of a standard BMC formulation by recycled materials does not significantly alter the mechanical properties. Increasing the amount of recyclate results in processing difficulties in the case of the glass fibers or a serious decline of the mechanical properties in the case of the filler/polymer. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070571116
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  • 8
    Electronic Resource
    Electronic Resource
    Flow-induced structure and rheology of a triblock copolymer (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 1585-1600 
    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: Linear viscoelastic properties are found to be a sensitive measure of flow-induced structural changes in a block copolymer. Styrene-butadiene-styrene block copolymer (SBS) with 26% polystyrene (PS) forms a macrostructure in the quiescent state with grains of the order of 1-10 μm. Within each grain, phase separation gives rise to a regular two-phase microstructure with cylindrical PS domains with radius of the order of 200 Å. Large-amplitude oscillatory shear (γ = 4.5) at temperatures between 139 and 181°C was applied to after the grain structure with the objectives of removing the discontinuities at the grain boundaries and of aligning the domains into a continuous ultrastructure. The SBS behaved like a solid (tan δ 〈 1 at low ω) before and like a liquid (tan δ 〉 1) after shear modification. This change expressed itself in the removal of the long relaxation times from the linear viscoelastic spectrum; the intermediate and low relaxation times were not affected by the shear modification. The viscoelastic spectrum slowly recovered during annealing with recovery times of the order of the longest relaxation time of the quiescent structure. Birefringence studies showed that the SBS did not recover into its original grain structure but into a highly oriented domain structure. The discontinuities at the grain boundaries could not be removed completely.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330514
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  • 9
    Electronic Resource
    Electronic Resource
    Study of the beam-foil excitation mechanism by use of sulfur and chlorine projectiles (1988)
    Springer
    The European physical journal 10 (1988), S. 457-466 
    Details
    ISSN: 1434-6079
    Keywords: 34.50.Fa ; 34.70.+e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Experimental relative level population data have been analysed for beam-foil excited S VI at 3 MeV and C1 VII at 5.5 MeV. For S VI, the level population is fairly independent of the principal quantum numbern (4≦n≦9), whereas a pronounced maximum is found for levels withn=8 in Cl VII. A two-step model has been applied to calculate theoretical values for the relative level populations. Satisfyingly good agreement is found between experiment and theory. The results confirm the previously proposed idea that at these fairly low projectile velocities, final projectile levels whose binding energies are comparable to or smaller than the binding energies for electrons in the valence band of the foil are mainly populated by transfer of valence band electrons, when the projectile leaves the foil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425764
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  • 10
    Electronic Resource
    Electronic Resource
    Capture of polarized electrons into excited terms of fast atoms during grazing surface collisions (1992)
    Springer
    The European physical journal 23 (1992), S. 41-53 
    Details
    ISSN: 1434-6079
    Keywords: 34.50.Fa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Fast ions are scattered from magnetized surfaces under grazing angles of incidence. During the interaction with the surface charge exchange is effective and results in a population of stable and excited atomic terms. This capture of electrons is characterized by anisotropic distributions of atomic orbital angular momenta and in addition — for magnetized targets — by anisotropic distributions of electronic spins. We will discuss in some detail, how these anisotropic distributions can be studied via the analysis of the state of polarization of the fluorescent light, emitted in electronic transitions from excited terms of free atoms after the impact with the surface. We show that a defined variation of the magnetization of the target affects the polarization of the emitted light in a characteristic way, which allows to deduce the electronic spin polarization of the atoms. The method implies some perspectives with respect to the study of magnetic properties of the vacuum-solid interface well above the topmost layer of surface atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436701
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