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- 1993 (117) (entfernen)
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- 2,2´-Bipyridyl-3,3´-diol (1)
- Acidification (1)
- Atemschutz (1)
- Binnenschiffe (1)
- CC (1)
- CCB (1)
- CCF (1)
- Cation dependence (1)
- Composites (1)
- CuHDO (1)
Eingeladener Vortrag
- nein (39)
Number-average molecular weights and inherent viscosities were found for the soluble members of an alkoxy-substituted copolyester series. A liquid-crystalline (high-temperature) phase was distinguisehd by IR and wide-angle X-ray scattering on molten and quenched samples in form of a nematic sanidic phase. In this phase no relationship exists between the orientation of the aromatic polyester backbone and that of the laterally attracted alkoxy groups. Further, it was proven by IR that only the polyester backbone can be aligned by shear stress. If the applied shear stress is very strong, the orientation of the stiff backbone becomes sensitive to disturbance caused by mechanical forces.
Schwerpunkte sind die Untersuchungen zur Fortführung der Analyse des Einflusses der Mehrachsigkeit des Spannungszustandes auf das Risswiderstandsverhalten, um damit das lokale stabile Risswachstum in Bauteilen besser verstehen und sicher beurteilen zu können sowie die Weiterentwicklung des Verfahrens zur Bestimmung von Risswiderstands - Kennwerten aus dem Kerbschlagversuch.
Bei elektrisch isolierenden Polymeren kann durch Beimischung leitfähiger Partikel eine Leitfähigkeit erreicht werden. Polymere mit einem strukturell geordneten, ungesättigten Polymerkörper besitzen bereits eine intrinsische Leitfähigkeit. Dünne Polymerschichten, wie sie mit Plasmaverfahren erzeugt werden, unterscheiden sich ganz wesentlich in ihrer Struktur von den klassischen Polymeren. So besitzen Plasmapolymerschichten aus leitfähigen Polymeren nur sehr geringe Leitfähigkeiten. Diese kann durch eine Dotierung mit Jod bei erhöhter Temperatur verbessert werden. Da eine Dotierung während des Plasmaprozesses mit elementarem Jod schwierig ist, wurde am Fraunhofer-Institut für Angewandte Materialforschung ein neues Plasmaverfahren entwickelt und in einer Laboranlage erprobt. Die Anlage arbeitet mit einem Argon-Mikrowellenplasma, dem jodhaltige aromatische Monomere (2-lodthiophen) zugesetzt wird. Die elektrische Leitfähigkeit der erzeugten Plasmapolymerschicht ist gut; ihr Aufbau und molekulare Struktur wurden mit ESCA und IR-Spektroskopie untersucht.
Structural investigations of electrical conducting plasma polymerized films from 2-iodothiophene
(1993)
Thin plasma polymerized films were produced in a microwave (2.45 GHz) plasma discharge using 2-iodothiophene as the initial monomer. The structure of these electrically conducting films (10-6-10-1 S/cm), the chemical state of the doping element iodine and the elemental homogeneity at the surface and in the films have been investigated by XPS, FTIR and AES. An interesting relationship was found that indicates some similarity to conventional polythiophene, prepared by electrodeposition. Besides covalently bound iodine, considerable amounts of I 3- and I 5- were detected and also a small number of O-I bonds were identified.
Intrinsically conductive plasma polymers were formed in a 2.45 GHz microwave low pressure plasma. The electrical conductivity and structure of the polymeric films were compared with those of electrochemically polymerized polythiophene. A new method of doping was tested using the iodine-containing monomer 2-iodothiopene. Films with high electrical conductivity (10-1 down to 10-6 S cm-1) could be produced, and their chemical structure was studied by X-ray photoelectron spectroscopy and Fourier transform IR spectroscopy. The IR spectra give a strong indication that the chemical structure of these films is comparable with that of electrochemically deposited polythiophene. Optical emission spectroscopy was used to give in-situ information about the fragmentation mechanism in the plasma.
The photophysical behavior of poly(p-phenylphenylenevinylene) (PPPV) and several oligomeric
model compounds in isotropic and anisotropic samples is investigated by means of polarized fluorescence
spectroscopy. As long as excitation energy transfer and mutual alignment are considered, the behavior of
PPPV can be modeled by a chain consisting of a distribution of independent oligomeric segments. The
results of fluorescence polarization, e.g., the nonzero value of r in isotropic PPPV, cast doubt on the application
of the semiconductor band model but favor an interpretation of spectroscopic properties in terms of molecular
transitions. The orientation coefficients of the oligomers and of PPPV in stretched polyethylene are determined.
The change of fluorescence spectra of oriented PPPV in stretched polyethylene demonstrates directly that
conformational changes of the macromolecule influence the pathway of energy transfer.
Plasma polymerization - A process for the preparation of thin intrinsically conducting coatings
(1993)
An Advanced Equipment for Single-Fibre Pull-Out test designed to monitor the fracture process
(1993)
Investigations on the cold crystallization of pure and filled PETP by dielectric measurements
(1993)
The cold crystallization of pure and filled poly(ethylene terephthalate) (PETP) after quenching from the melt has been investigated by dielectric measurements in two different modes: The first one using constant heating-rate (in the temperature range from 320 to 480 K) and the second one under isothermal conditions (at 378 K). The complex dielectric constant (ε´, tan δ) is influenced by crystallization. Two α-relaxation regions are identified: The αa-relaxation region from the pure amorphous phase and the α´-relaxation region from the spherulitic phase. The investigations on the filled systems (PETP + 10% aramid puple, PETP + 30% short glass fibres) prove that an influence of the fillers on the time delay and rate of crystallization and on the geometry of the growing spherulites exists.
In situ second harmonic generation measurements during the electrodeposition of Ni on n-Si(111)
(1993)
Tribology and New Materials
(1993)
Decorative hard coatings: interdependence of optical, stoichiometric and structural properties
(1993)
Isotrope nichtlineare Viskoelastizität mit Hilfe von Maßstabsfunktionen der Gedächtnisspannung
(1993)
Seismische Verfahren zur Untergrunderkundung und Ermittlung von Materialkennwerten des Bodens
(1993)
Überwachung des Schädigungsprozesses eines Stahlbeton-Zweifeldträgers mit dynamischen Methoden
(1993)
Zur lokalen Verteilung der Photonen- und Neutronenaktivierung in Bleifolien bei LINAC-Bestrahlung
(1993)
The paper descibes a novel method to detoxify pine wood (Pinus silvestris L.) treated with CCB-, CCF- CC-, and Cu-HDO-type salt preservatives. In the process of biological detoxification organic acids produced by strains of Antrodia vaillantii and other brown rot fungi are used for the dissolution of the previously fixed inorganic compounds. These findings are the basis for applying an acid pulping process (FORMACELL) developed by Nimz and Schone (1992) at the BFH, Hamburg, to detoxify salt impregnated wood waste with a mixture of acetic and formic acid. First results achieved with wood chips from treated poles after approximately 20 years of service life show that the obtained pulp contains less than 100 ppm of Cr and Cu. The pulp properties were neither influenced by the Cr and Cu ions nor by the age of the poles. The extracted quantities of Cr and Cu remain with the lignin whereas the acids are evaporated and recycled in the pulping process.