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
    Influence of physical ageing on the α dielectric relaxation of poly(methyl acrylaie) (1985)
    Springer
    Polymer bulletin 14 (1985), S. 45-52 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work are examined changes of the α relaxation spectrum of PMA during the structural relaxation process which follows a quenching from a temperature To above Tg to another T1 below Tg, which is mantained constant. It is found that the relaxation times spectrum is shifted towards longer times as the ageing time increases. At the same time, its form becomes more and more wide, approaching the form of the relaxation times spectrum calculated at temperatures above Tg from alternative dielectric measurements. A parameter measuring the shift of the spectrum, a(ta), is defined and its dependence on ageing time and annealig temperature is studied. The effective relaxation time of the structural relaxation process is calculated from a(ta) and it is found dependent on the temperature of annealing as well as on the value of a(ta)itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254914
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Dynamic mechanical behaviour of poly(methyl acrylate) reinforced by poly(ethylene terephthalate) fibres (1989)
    Springer
    Journal of materials science 8 (1989), S. 263-264 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00725491
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    On the dynamic mechanical behavior of poly(ethyl methacrylate) reinforced with kevlar fibers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1647-1657 
    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 dynamic mechanical relaxation spectra of a series of composites with a matrix of poly(ethyl methacrylate) reinforced with continuous Kevlar fibers present several characteristics that have been proposed in the literature regarding polymer composites as a proof of the existence of an interphase between the polymeric matrix and the filler with mechanical properties different from both: The α-relaxation, associated with the glass transition of the matrix, is shifted in the temperature axis, and a peak appears in the tan δ vs. temperature plot, which was not present either in the matrix or in the fiber relaxation spectra. Nevertheless, a simple block model which does not include the existence of such an interphase is able to reproduce not only the dependence of the loss tangent and storage modulus with the fiber content, but also the shift of the α-relaxation and the presence of the new α′ peak in the composites.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420619
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Influence of the thermal history on dielectric properties of poly(vinyl chloride) (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 845-848 
    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: In this paper, we report dielectric permittivity and loss of poly (vinyl chloride) samples that have received three different thermal treatments: (a) as received, (b) quenched from 110°C to 20°C and (c) slow cooled at 5°C/h. There are several observations: first, the secondary (β) loss peak-is not representative of a simple mechanism of transition, in agreement with results of other authors (10), second, in the glass transition zone, there are clearly two peaks (α1 and α2) - α1, is a typical peak of an amorphous glass transition; the second, α2, has possibly a crystalline origin - and, third (and the most interesting fact), there is an increase of the loss tangent in the intermediate zone between α and β peaks showing a new relaxational peak with high activation energy (70 Kcal/mole), in agreement with dynamic mechanical results (6).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221311
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Dielectric relaxation study of low-density polyethylene by thermally stimulated depolarization currents and thermal sampling (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 1645-1653 
    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 dielectric relaxation zone of a low-density polyethylene has been studied by thermally stimulated depolarization currents (TSDC) and thermal sampling (TS). Three relaxations have been found in this zone, which have been labeled γI, γII, and γIII in decreasing order of temperature. Samples of different crystallinities were subjected to several thermal treatments in order to study the molecular origin of each relaxation. The γI relaxation intensity changes with the thermal treatment, while the intensity of the γI relaxation is only slightly modified. Using TS it has been proved that the γI relaxation fulfils the compensation law with a high level of significance. Nevertheless, the experimental data are not enough to verity the γI and γIII relaxation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370617
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Dielectric relaxations in poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate) (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1145-1157 
    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: A comparative study is undertaken of the dielectric relaxation spectra of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate), taking into consideration the spectra of the corresponding polymers in the series of the polymethacrylates. The three polymers, PMA, PEA, and PBA, present an α relaxation zone clearly separated from the secondary relaxations. Its shape is not altered with temperature, and it is possible to construct a master curve. With increasing length of the side chain, its distribution of relaxation times broadens and the temperature of the maximum of the relaxation decreases. A β relaxation with decreasing intensity as the length of the side chain increases is clearly perceptible in PMA and PEA, but almost not perceptible at all in PBA. In PEA this relaxation appears split into two peaks. Computer simulation of restricted motions of the side chain discard an origin similar to that of the γ relaxation in PPA or PBA for the lowest temperature component of the relaxation, and suggests the conjunction of two rotation mechanisms in this relaxation for the polyacrylates. For the experimental temperatures of our tests a γ relaxation shows up only in PBA. Its apparent activation energy, higher than in related polymers of the polymethacrylate series, suggests that the tighter packing of monomeric units in polyacrylates leads to a significant increase in the intermolecular contribution to the potential energy barrier responsible for the relaxation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380612
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Effect of the cooling rate in the formation of glass on the α and β relaxations of some amorphous polymers (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1202-1204 
    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 has been observed in dynamic mechanical measures that the range of temperatures in which relaxation properties are affected by the diminishing of the free volume has, as a lower limit the temperature at which the maximum of G″ or tgδ, corresponding to the β relaxation, occurs. In dielectric measures on polymers in which the β relaxation is not predominant over the α relaxation, this temperature range is scarcely affected by changes in frequency, whereas the peak shifts according to its activation energy. This fact leads to the conclusion that the decrease in free volume due to a slow cooling from a temperature above Tg mainly affects mobility of the main chains under Tg, without disturbing the groups that give rise to the secondary relaxations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241509
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Structural relaxation of glass-forming polymers based on an equation for configurational entropy, 4. Structural relaxation in styrene-acrylonitrile copolymer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2201-2217 
    Details
    ISSN: 0887-6266
    Keywords: structural relaxation ; physical aging ; differential scanning calorimetry ; configurational entropy ; enthalpy relaxation ; heat capacity ; styrene-acrylonitrile copolymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structural relaxation process in styrene-acrylonitrile copolymer has been characterized by means of differential scanning calorimetry (DSC) experiments. The results in the form of heat capacity, cp(T), curves are analyzed using a model for the evolution of the configurational entropy during the process recently proposed by the authors.11,12 The model simulation allows one to determine the enthalpy (or entropy) structural relaxation times and the β parameter of the Kohlrausch-Williams-Watts equation characterizing the width of the distribution of relaxation times. This material parameters are compared with their analogues determined from the dielectric and dynamic-mechanical relaxation processes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2201-2217, 1997
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 9
    Electronic Resource
    Electronic Resource
    Depolarization thermocurrent studies in poly(hydroxyethyl acrylate)/water hydrogels (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1001-1008 
    Details
    ISSN: 0887-6266
    Keywords: hydrogels ; water in poly(hydroxyethyl acrylate) ; dielectric relaxation ; thermally stimulated depolarization currents (TSDC) ; glass transition ; space charge polarization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Detailed investigations on the dielectric relaxation mechanisms in poly(hydroxyethyl acrylate) (PHEA), by means of the thermally stimulated depolarization currents (TSDC) method in the temperature range 77-300 K are reported. There is particular interest in the dependence of the dielectric relaxation mechanisms on the water content h, h = 0 - 0.5 w/w, in an attempt to contribute to a better understanding of the physical structure of water in the PHEA hydrogels. We employ thermal sampling (TS) and partial heating (PH) techniques to experimentally analyze the observed complex relaxation processes, due to the secondary (βsw) and the main (α) relaxation, into approximately single responses and to determine the spectra of activation energies E(T) at different h values. Measurements with different electrode configurations reveal different aspects of the dynamics of the relaxation mechanisms and allow the distinction between dipolar and conductivity relaxation contributions. It is shown that by means of these techniques we can determine certain temperature characteristics for the α relaxation and investigate their dependence on water content. We discuss the relation of these characteristic temperatures to the calorimetric glass transition temperature Tg. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320605
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Application of the method of brather for the determination of complex dielectric permittivity from measurements of isothermal polarization current (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 1505-1511 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some years ago, Brather proposed a method for calculation of the real and imaginary parts of the complex dielectric permittivity starting from measurements of isothermal polarization current. This method shows some advantages over the Hamon method, which is normally used. Both methods are applied in this work to the β relaxation of poly(butyl methacrylate). It is concluded that, with the usual accuracy of measurement, a combination of the two methods is advisable; Hamon's method is taken to be a first approximation to that of Brather. Results following the two procedures are compared, and their respective advantages and disadvantages are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230804
    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...