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Kombination von Ultraschallspektroskopie und Dilatometrie zur Analyse der Strukturbildung während der Kristallisation von Polymeren unter Druck

Ohneiser, Alexander (2011):
Kombination von Ultraschallspektroskopie und Dilatometrie zur Analyse der Strukturbildung während der Kristallisation von Polymeren unter Druck.
TU Darmstadt, [Online-Edition: urn:nbn:de:tuda-tuprints-26050],
[Ph.D. Thesis]

Abstract

Isothermal crystallization experiments of isotactic polypropylene at moderate pressure have been carried out using a new measuring cell. By a combination of pressure dilatometry and ultrasound spectroscopy it was able to measure simultaneously specific volume, longitudinal ultrasound velocity and excess attenuation coefficient during glass transition or crystallization. It was shown, that pressure dilatometry as well as ultrasound spectroscopy can be applied to analyse the crystallization process in polymers. Both methods allow detection of fast and very slow crystallization mechanisms and yield comparable results. By means of Hoffman-Lauritzen theory it was shown, that acceleration of crystal growth under the influence of pressure can be attributed to the shift of the characteristic transition temperatures. In addition to the systematic crystallization experiments the excess attenuation coefficient, which was measured during crystallization from the melt up to the semi-crystalline solid state, was analyzed. It was found, that ultrasound excess attenuation mainly arises from sound scattering at the boundaries of spherulites and because of molecular relaxation processes, which might lead back to the rigid amorphous fraction in between the crystal lamellae.

Item Type: Ph.D. Thesis
Erschienen: 2011
Creators: Ohneiser, Alexander
Title: Kombination von Ultraschallspektroskopie und Dilatometrie zur Analyse der Strukturbildung während der Kristallisation von Polymeren unter Druck
Language: German
Abstract:

Isothermal crystallization experiments of isotactic polypropylene at moderate pressure have been carried out using a new measuring cell. By a combination of pressure dilatometry and ultrasound spectroscopy it was able to measure simultaneously specific volume, longitudinal ultrasound velocity and excess attenuation coefficient during glass transition or crystallization. It was shown, that pressure dilatometry as well as ultrasound spectroscopy can be applied to analyse the crystallization process in polymers. Both methods allow detection of fast and very slow crystallization mechanisms and yield comparable results. By means of Hoffman-Lauritzen theory it was shown, that acceleration of crystal growth under the influence of pressure can be attributed to the shift of the characteristic transition temperatures. In addition to the systematic crystallization experiments the excess attenuation coefficient, which was measured during crystallization from the melt up to the semi-crystalline solid state, was analyzed. It was found, that ultrasound excess attenuation mainly arises from sound scattering at the boundaries of spherulites and because of molecular relaxation processes, which might lead back to the rigid amorphous fraction in between the crystal lamellae.

Uncontrolled Keywords: Dissertation, Ultraschallspektroskopie, Polymer, Kristallisation, DKI, TU Darmstadt, Ohneiser, Alig
Divisions: 11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Structure Research
05 Department of Physics > Institute of Applied Physics
05 Department of Physics > Institute for condensed matter physics
05 Department of Physics > Institute for condensed matter physics > Experimental Condensed Matter Physics
07 Department of Chemistry > Fachgebiet Makromolekulare Chemie
07 Department of Chemistry > Physical Chemistry
11 Department of Materials and Earth Sciences
05 Department of Physics
07 Department of Chemistry
Date Deposited: 28 Jun 2011 12:09
Official URL: urn:nbn:de:tuda-tuprints-26050
License: Creative Commons: Attribution-Noncommercial-No Derivative Works 3.0
Referees: Alig, Priv.-Doz. I. and Stühn, Prof. Dr. B.
Refereed / Verteidigung / mdl. Prüfung: 7 February 2011
Alternative keywords:
Alternative keywordsLanguage
ultrasound spectroscopy, polymer, crystallizationEnglish
Alternative Abstract:
Alternative abstract Language
Mittels einer neuartigen Messzelle wurden isotherme Kristallisationsexperimente an isotaktischem Polypropylen unter Druck durchgeführt. Durch die Kombination von Druckdilatometrie und Ultraschallspektroskopie war eine simultane Messung von spezifischem Volumen, longitudinaler Schallgeschwindigkeit und Ultraschallexzessdämpfung während des Glasübergangs oder der Kristallisation möglich. Es wurde gezeigt, dass sich sowohl die Druckdilatometrie als auch die Ultraschallspektroskopie zur Analyse der Polymerkristallisation eignen. Beide Methoden erlauben die Untersuchung von schnellen und sehr langsamen Kristallisationsvorgängen und liefern vergleichbare Resultate. Im Rahmen der Hoffman-Lauritzen-Theorie wurde gezeigt, dass die Beschleunigung des Kristallwachstums unter Druck auf die Verschiebung der charakteristischen Übergangstemperaturen zurückgeführt werden kann. Neben den systematischen Untersuchungen zur Druckabhängigkeit der Kristallisationskinetik wurde die Ultraschallexzessdämpfung analysiert. Hierbei konnte festgestellt werden, dass die Ultraschalldämpfung im Wesentlichen durch die Beiträge von Schallstreuung an den Korngrenzen der Sphärolithe sowie durch Verluste aufgrund molekularer Relaxationen innerhalb der steif amorphen Phase begründet ist.German
Isothermal crystallization experiments of isotactic polypropylene at moderate pressure have been carried out using a new measuring cell. By a combination of pressure dilatometry and ultrasound spectroscopy it was able to measure simultaneously specific volume, longitudinal ultrasound velocity and excess attenuation coefficient during glass transition or crystallization. It was shown, that pressure dilatometry as well as ultrasound spectroscopy can be applied to analyse the crystallization process in polymers. Both methods allow detection of fast and very slow crystallization mechanisms and yield comparable results. By means of Hoffman-Lauritzen theory it was shown, that acceleration of crystal growth under the influence of pressure can be attributed to the shift of the characteristic transition temperatures. In addition to the systematic crystallization experiments the excess attenuation coefficient, which was measured during crystallization from the melt up to the semi-crystalline solid state, was analyzed. It was found, that ultrasound excess attenuation mainly arises from sound scattering at the boundaries of spherulites and because of molecular relaxation processes, which might lead back to the rigid amorphous fraction in between the crystal lamellae.English
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