Filtern
Erscheinungsjahr
Dokumenttyp
- Beitrag zu einem Tagungsband (50)
- Zeitschriftenartikel (48)
- Beitrag zu einem Sammelband (42)
- Vortrag (42)
- Posterpräsentation (4)
- Monografie (1)
- Buchkapitel (1)
- Dissertation (1)
- Forschungsbericht (1)
Sprache
- Englisch (109)
- Deutsch (80)
- Mehrsprachig (1)
Schlagworte
- Weathering (39)
- Bewitterung (26)
- UV (15)
- Chemiluminescence (13)
- Artificial weathering (11)
- Spectral sensitivity (10)
- Künstliche Bewitterung (9)
- Alterung (6)
- Degradation (6)
- Action spectra (5)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (31)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (31)
- 3 Gefahrgutumschließungen; Energiespeicher (12)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (12)
- 6 Materialchemie (6)
- 8 Zerstörungsfreie Prüfung (6)
- 8.0 Abteilungsleitung und andere (6)
- 6.3 Strukturanalytik (5)
- 5 Werkstofftechnik (3)
- 4 Material und Umwelt (2)
Eingeladener Vortrag
- nein (42)
Polyether and -ester urethanes (PU) were exposed to artificial weathering at 40 °C and artificial UV radiation in a weathering chamber. In 3 parallel exposures, humidity was varied between dry, humid, and wet conditions. Material alteration was investigated by various analytical techniques like size exclusion chromatography
(SEC), liquid chromatography-infrared spectroscopy (LC-FTIR), thermal-desorption gas chromatography-mass spectrometry (TD-GC-MS), fluorescence mapping and dynamic mechanical analysis (DMA). Our results show that depending on the weathering conditions, different degradation effects can be observed. By means of SEC an initial strong decrease of the molar masses and a broadening of the mass distributions was found. After a material dependent time span this was followed by a plateau where molar mass changes were less significant. A minor moisture-dependent degradation effect was only found for polyester PU. Fluorescence measurements on two materials revealed an increase in the luminescence intensity upon weathering process reaching a saturation level after about 500 h. The changes in the optical properties observed after different exposure conditions and times were very similar. The TD-GC-MS data showed the fate of the stabilizers and antioxidant in the course of weathering. LC-FTIR measurements revealed a change in peak intensities and the ratio of urethane and carbonyl bands.
The thermo-oxidative degradation of a polymeric optical cable is investigated by chemiluminescence, The results are reliable and reproducible. Two distinct processes are reported marked by a peak and a plateau behavior versus the time, respectively. Both processes are ruled by thermally activated processes. Beside the dependencies of temperature and time, the influence of absorbed water is discussed. Chemiluminescence is proposed as a promising candidate for a suitable testing method assessing the thermo-oxidative stability of plastic optical fibers and cables. it requires not more than a simple one-day testing procedure and has the advantage that it can be carried out even within the lo cv temperature ranges of the cables' intended use.
Polarized fluorescence and orientational order parameters of a liquid-crystalline conjugated polymer
(1999)
We report a study of the orientational order of aligned thin films of the liquid crystalline conjugated polymer poly(9,9-dioctylfluorene). Steady state polarized fluorescence measurements were used to determine the orientational order parameter <P2> and <P4>. The influence of intermolecular and intramolecular excitation energy transfer on the degree of polarization is discussed. The role of film morphology is also examined by comparison of the results for glassy and crystalline films.
A liquid crystalline mainchain conjugated polymer for polarized electroluminescence applications
(1997)
Polarized fluorescence and orientational order parameters of a liquid crystalline conjugated polymer
(1999)
The excitation energy transfer (EET) of a bichromophoric cross-shaped molecule was investigated by stationary polarized fluorescence spectroscopy in the solid state. For this purpose 2,2[prime],7,7[prime]-tetrakis(biphenyl-4-yl)-9,9[prime]-spirobifluorene was embedded in a polymeric bisphenol-A-polycarbonate (PC) matrix. The dependence of the fluorescence on concentration and wavelength was determined. The role of the intermolecular and intramolecular EET is dealt with separately and discussed by means of the degree of polarization. The intermolecular excitation energy transfer is described in terms of a Förster transfer mechanism. The intramolecular transfer is prevented for the zero-point vibrational levels by the molecular cross-shaped structure, but is found for a wide range of wavelength, presumably based on vibrationally excited states.
In den letzten Jahrzehnten wurde die Degradation der polymeren Matrix von flammgeschützten Polymeren eingehend untersucht. Erst in den letzten Jahren jedoch hat sich die Frage der Lebensdauer der Funktionalität des Flammschutzes selbst als wichtige Fragestellung herauskristallisiert, z.B. bei Kabeln. Deshalb sollte diese Fragestellung durch systematisch-variierte künstliche Klima- und Bewitterungstests an flammgeschützten Polymerwerkstoffen untersucht werden