ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Some phenomenological relaxation rate equations based on Bose–Einstein similar kinetics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5179-5186 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The possibility of describing transient phenomena associated with flow and consolidation of solids, such as stress relaxation or physical aging, in terms of a kinetic mechanism comprising spontaneous and induced events is discussed. The starting point is the differential equation dn(overdot)/dt=−an(overdot)[1−(b/a)n(overdot)], with n denoting the number of relaxed entities and n(overdot)=dn/dt (a,b are constants, t is time), yielding an n(overdot)(t) function reminiscent of a Bose–Einstein distribution. The corresponding n(t) relation describes the linear variation of n with log t, and the exponential dependence of n(overdot) on n, as often found experimentally. Replacing n(overdot) in the starting equation by the relative rate n(overdot)/n yields a power-law-type n(overdot)(n) dependence. A further modification, where the induction term n(overdot)/n is not linear but raised to a power (approximately-greater-than)1, finally produces a generalized version of the stretched exponential. When interpreted formally in terms of a spectrum of relaxation times τ, all three equations produce response functions with discrete τ distributions, provided a≠0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351998
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Superimposed transition mechanisms in polyvinylchloride (1974)
    Springer
    Rheologica acta 13 (1974), S. 490-494 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Summary Studies have been made of the viscoelastic behaviour of PVC in the glass-rubber transition by means of square and triangular periodic stresses, in order to find a plausible hypothesis on the appearing molecular mechanisms. In this respect it is obviously not possible to make a detailed analysis of the different types of mechanisms, based only on results from dynamic mechanical measurements. However, by using the general properties of the function logJ 2 =g α {logJ 1} some ideas can be put forward. It is apparent that the viscoelastic behaviour stems from more than one single molecular mechanism. “Simple segment movements” dominate the behaviour only in the central part of the transition. At temperatures around the glass point an increase in losses and/or stiffness appears. It seems possible that this behaviour arises from the influence of the crystallites. At high temperatures a substantial increase in mechanical losses appears, which seems to be due to decomposition of “widely spaced entanglements”. In the plateau-zone a secondary dispersion appears which shows pronounced sensitivity to the processing conditions. At increased gelation ratio the value of the loss peak increases. As no changes in crystallinity have been observed, it is suggested that this dispersion originates from the decomposition of “untrapped entanglements” outside the network composed by the very small crystallites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01521745
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Studies of relaxation phenomena in polymers. I. The use of periodic square and triangular stress functions (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2965-2975 
    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: In order to evolve the methods of mechanical spectroscopy and find new methods of studying the rise of nonlinear viscoelasticity, periodic square and triangular stress functions have been used. A “new” viscoelastic function is defined, log J2 = g{log J1}, where J1 and J2 are the compliances at the time (ζ/2 + 2nζ)n→∞ for an odd, periodic, square function and an even, periodic, triangular function, respectively, with periods of 2ζ. The function shows characteristic shapes for viscoelastic spring and dashpot models. The interrelations between the complex compliance and J1 and J2 are developed; and since the sum of J1 and J2 at the time ζ/2 agrees very well with the creep compliance at the same time, J1 and J2 can be used as an interrelation between complex compliance and creep compliance. Special equipment for measuring the compliances J1 nd J2 is described.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070171004
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Studies of relaxation phenomena in polymers. IV. Superimposed transition mechanisms in polymethacrylates (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2997-3002 
    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: The existence of superimposed transition mechanisms in the “Tg region” of polymethacrylates has been indicated by several authors including Ferry and co-workers, who also have tried to separate the mechanisms. Using the general properties of the viscoelastic function logJ2 = gα {log J1} and a simple weighting model, the α-and β-mechanisms have been separated. The viscoelastic function log J2 = gβ{log J1} is determined and is found to coincide both where different polymethacrylates are concerned and for the calculated as well as the directly measured data.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070171007
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The limits of linear viscoelasticity in poly(methyl methacrylate) and poly(ethyl methacrylate) (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 1971-1978 
    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: The limit of linear viscoelasticity is determined for poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) in uniaxial tension creep over the temperature range of 20° to Tg -10°C. The time span covered is from 10 to 1000 sec. The linear limit is defined as the point at which the creep compliance deviates by more than 1% from its mean value in the linear viscoelastic range. For both materials, the stress limit of linear viscoelasticity falls to a minimum or plateau level at a temperature below Tg. It is suggested that the β-mechanism plays an important role in the existence of this minimum.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1975.070190717
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Selective etching of thermotropic liquid crystalline polyesters (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 743-762 
    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: DSC, IR, ESCA, macroscopic etching rate measurements, analysis of etchant solution, and electron microscopy conclusively show that n-alkylamines (ethylamine, n-propylamine, n-butylamine, and n-pentylamine) and NaOH selectively degrade (etch) the ethylene terephthalate (ET)-rich phase in glassy liquid crystalline poly(p-hydroxybenzoic acid-co-ethylene terephthalate) [P(HBA-ET)] with molar compositions 0.60:0.40 and 0.80:0.20. ESCA demonstrates the excellent selectivity of the n-alkylamine etchants in the 0.60:0.40 copolymer. The 50 Å top layer of the etched samples contains 95 mol% HBA. Treatment with H2SO4 and NH3 gives ambiguous results, and these compounds are not suitable as etchants. It is demonstrated by electron microscopy on the 0.60:0.40 copolymer, in accordance with earlier reports by Joseph et al.,5-8 that the ET-rich phase is discontinuous (1-2 μm spheres) and surrounded by an HBA-rich matrix. SEM is a useful tool for characterization of this morphology. However, both phases have a substracture which is revealed only by TEM. The morphology of the 0.80:0.20 copolymer is fine-textured, which means that SEM is a less suitable method for the characterization of etched samples.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070340226
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Studies of relaxation phenomena in polymers. II. The behavior of simple polymers in their main transition region (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2977-2986 
    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: In an earlier paper, a “new” viscoelastic function, log J2 = g{log J1}, was defined. For polymers, the linear viscoelastic behavior of which is characterized by “simple segment movements” in their main transition regions, the following general properties are found: (1) The local maxima of the function for different polymers fall along a straight line width the slope approximately equal to 1.1. (2) A characteristical general shape is noticed for the function after shifting along the straight line and reducing the J1 compliance as regards the “frozen in” compliance J10. (3) J1 reflects the storage and J2, the loss mechanisms of the system. The relation J2/J1 is an expression for the average retardation time.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070171005
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Studies of relaxation phenomena in polymers. III. Superimposed transition mechanisms in polyisobutylene and poly(vinyl acetate) (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2987-2996 
    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: Based on the general properties of the function log J2 = gα{log J1}, discussed in earlier papers,1,2 the existence of two superimposed dispersion mechanisms in the glass-rubber transition of polyisobutylene (PIB), and poly(vinyl acetate) (PVAc) is discussed. A simple weighting model is used for separation of the two mechanisms. For the interpretation of the β-mechanism, in PIB, the following facts are taken into account: (a) The loss maximum of the β-mechanism appears in a zone where only very reduced segment movements occur. (b) The methyl side groups in PIB require special conformations of the main chains before they can rotate. (c) The apparent activation energy for the β-mechanism is approx. 20 kcal/mole. Thus, for PIB the following interpretations for the α- and β-mechanisms are proposed: (1) The α-mechanism is due to simple segment movements. (2) The β-mechanism appearing in the “Tg region” is due to coupled movements between the main chain and methyl side groups. The ester groups of poly(vinyl acetate) need a lot more space for their rotations than the carboxy groups of poly(methyl acrylate) and can be expected to give considerable steric hindrance. It is therefore reasonable to suppose that a transition mechanism similar to the β-mechanism of polymethacrylates will appear in the “freezing” region of poly(vinyl acetate). The analysis of the β-mechanism is made using the same separation method as for polyisobutylene.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070171006
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    The appearance of non-linear viscoelasticity in polyethyl methacrylate (1974)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 37 (1974), S. 27-34 
    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: Die Entstehung von nicht-linearer Viskoelastizität in Polyäthylmethacrylat bei reiner Schubverformung wurde mit Hilfe periodischer, quadratischer und triangulärer Spannungsfunktionen untersucht.Die Untersuchung zeigt, daß der β-Übergang am viskoelastischen Verhalten einen beträchtlichen Anteil hat, und daß eine Erhöhung der Spannungsabhängigkeit in dem Zeit-Temperaturbereich auftritt, wo die Wirksamkeit der β-Mechanismen normalerweise zu erwarten ist.
    Notes: The appearance of non-linear viscoelasticity in polyethyl methacrylate has been studied in pure shear by means of periodic, square and triangular stress functions.It is shown that the β-transition gives a considerable contribution to the non-linear behaviour and that an increase in the stress dependence appears in the time-temperature region where the β-mechanisms are expected to act.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1974.050370103
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Injection molding of polypropylene discs. I: Effect of holding pressure on orientation distribution (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 950-956 
    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: It is well known that the injection molding process has a major impact on the properties of injection-molded polymers. In this study, the effect of the holding pressure on the orientation in injection-molded discs of polypropylene has been examined. The orientation has been determined by IR-dichroism and the orientation factors calculated according to Herman's orientation function, the average factor as well as the crystalline and the amorphous. The distribution of the orientation in the length as well as in the depth direction has also been exmined in order to understand how the flow has propagated in the cavity during both the filling and the packing phases. The results show that the holding pressure clearly affected the orientation, but that it was an unevenly distributed effect over the disc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760351109
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...