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- Weathering (13)
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- Degradation (4)
- Flame retardant (4)
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Organisationseinheit der BAM
- 7 Bauwerkssicherheit (14)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (14)
- 6 Materialchemie (5)
- 6.3 Strukturanalytik (4)
- 3 Gefahrgutumschließungen; Energiespeicher (3)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (3)
- 5 Werkstofftechnik (3)
- 4 Material und Umwelt (2)
- 5.3 Polymere Verbundwerkstoffe (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
Degradation effects of automotive coatings after weathering as detected by thermoluminescence
(2004)
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.
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.