Zeit-Temperatur-Verschiebung von thermoplastischen polymeren Werkstoffen

Translated title of the contribution: Time-temperature superposition of thermoplastic polymer materials

Andreas Moser

Research output: ThesisMaster's Thesis

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Abstract

Time-temperature-superposition is a valuable tool for describing the viscoelastic behaviour of linear (thermorheological simple) polymers over a broad range of times or frequencies. For the condition of linear-viscoelastic behaviour the broad range of application is obtained by horizontal shifting of data obtained at several temperatures to a predefined reference temperature. In case of branched (thermorheological complex) polymers or non linear-viscoelastic behaviour the time-temperature-superposition requires an additional vertical shift. Therefore this technique involves the use of temperature dependent shift factors for vertical and horizontal shift on log-log plots of material functions such as the relaxation modulus, the storage and loss moduli, and the creep compliance. The temperature dependent horizontal shift factor a_T multiplies the frequency or divides the time to yield a reduced value equal to aT*ω or t/aT. In addition the temperature dependent vertical shift factor b_T multiplies the given modulus bT*G. If time-temperature-superposition is valid the use of shift factors will yield a “master curve” showing viscoelastic behaviour over a large range of times or frequencies. In this work data for time-temperature-superposition was obtained from dynamic mechanical analysis of an amorphous and a semi-crystalline polymer. Verification of the validity of time-temperature-superposition was given by the use of a modified Cole-Cole-plot and a van Gurp-Palmen-plot. It was shown that both horizontal and vertical shifts were necessary to superimpose the dynamic modulus of the semi-crystalline (thermorheological complex) material, however the amorphous (thermorheological simple) polymer only needed a decent horizontal shift. The master curve for both materials were created at different loading conditions (pure shear, torsion, tension, bending) and the horizontal and vertical shift factors were compared to each other at the glass transition temperature. By calculation and comparison of the Arrhenius activation energy and the WLF constants the applicability for all loading conditions were demonstrated. With the semicrystalline polymer polymer-nanocomposites were compounded and compared to each other at a reference temperature which represents the α-relaxation process. Additionally a new method for gathering data for time-temperature-superposition was presented. This variothermal method eliminates the transient behaviour of commonly used isothermal segments. However this method only provides evaluable data when using specific sample geometries and process parameters. For analysing data of this variothermal method a new software program called “TTS+” was designed.
Translated title of the contributionTime-temperature superposition of thermoplastic polymer materials
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Feuchter, Michael, Co-Supervisor (internal)
  • Pinter, Gerald, Supervisor (internal)
Award date22 Mar 2013
Publication statusPublished - 2013

Bibliographical note

embargoed until null

Keywords

  • time-temperature-superposition
  • Arrhenius
  • WLF
  • nanocomposites
  • polypropylene
  • polystyrene
  • van Gurp
  • Palmen
  • Cole
  • vGP-plot
  • CC-plot
  • α-relaxation
  • layered silicates
  • dynamic-mechanic analysis
  • DMA
  • horizontal shift
  • vertical shift
  • activation energy

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