Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (27)
- Beitrag zu einem Tagungsband (18)
- Beitrag zu einem Sammelband (7)
- Posterpräsentation (7)
- Vortrag (2)
Schlagworte
- DMA (3)
- Phenolic resin (3)
- Dielectric loss and relaxation (2)
- Flammability (2)
- Glass transition (2)
- High pressure DSC (2)
- Macromolecular and polymer solutions (2)
- Melt mixing (2)
- Nanocomposite (2)
- Nanocomposites (2)
Eingeladener Vortrag
- nein (2)
Angesichts der spezifischen Bedeutung der Aushärtung von Phenolharzen für ihre Eigenschaften als Ingenieurwerkstoffe besteht großes Interesse an deren quantitativer Charakterisierung. Mittels DSC-Messungen unter hohem Druck (HP-DSC) kann die Vernetzungsreaktion der Phenolharzformmassen durch die Unterdrückung der Verdampfung niedermolekularer Substanzen ohne störende Überlagerungen verfolgt werden. Mittels verschiedener Vernetzungsgrade können die Einflussparameter der Aufheizrate und der Nachtemperung optimiert werden. Die Messergebnisse ermöglichen eine Modellierung der Reaktionskinetik mit dem Ziel einer verbesserten Prozessführung und Qualitätskontrolle in der industriellen Praxis.
Single-walled carbon nanotubes (SWNT) and carbon nitride films are synthesized by a direct current (dc) arc discharge at slightly reduced pressure and by an inductively coupled r.f. plasma (ICP) at atmospheric pressure, respectively. By treatment with nitric acid SWNT are purified from by-products and characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. ICP allows the deposition of carbon nitride films on steel substrate. The deposition of the films creates a relatively strong radial symmetric profile. The structure of the films are rather independent of the distance between substrate and plasma. Raman, Fourier transform infrared (FTIR), and energy dispersive X-ray (EDX) spectroscopy are used for analyzing the carbon nitride materials.
Linear segmented polyurethanes based on poly(butylene adipate)s (PBA) of different molecular weight (Mn 2000, 1000, and 600), 4,4-diphenylmethane diisocyanate (MDI) and the mesogenic diol 4,4-bis-(6-hydroxyhexoxy)biphenyl (BHHBP) as well as the unsegmented polyurethane consisting of MDI/BHHBP units have been synthesized and characterized by elemental analysis, 13C-NMR and SEC. The thermal behavior and the morphology were studied by DSC, polarizing microscopy, and DMA. The properties of the MDI-polyurethanes were discussed in relation to the BHHBP chain extended 2,4-TDI-polyurethanes and common 1,4-butanediol chain-extended MDI products. MDI polyurethanes based on PBA (Mn 2000) exhibit a glass transition temperature Tg of about -40°C independent of the hard segment content up to 50% hard segments. At higher hard segment contents increasing Tgs were observed. Polyurethanes, based on the shorter polyester soft segments PBA (Mn 1000 or 600), reveal an increase in the glass transition temperatures with growing hard segment content. The thermal transitions caused by melting of the MDI/BHHBP hard segment domains are found at 50 K higher temperatures in comparison with the analogous TDI products with mesogenic BHHBP/TDI hard segments. Shortening of the PBA chain length causes a shift of the thermal transitions to lower temperatures. Polarizing microscopy experiments indicate that liquid crystalline behavior is influenced by both the content of mesogenic hard segments and the chain length of the polyester. © 1996 John Wiley & Sons, Inc.