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In the framework of LMFBR safety analysis a theoretical interpretation of some of the most representative of the single pin experiments of the in-pile SCARABEE project has been performed from both viewpoints of themohydraulic and fuel behavior using the computer codes CAPRI-2 and SATURN-1. The analysis aimed at investigating the pin behavior from the preirradiation history, through the observed sequence of events following a coolant mass flow reduction from boiling inception up to pin breakdown. A comparison of theoretical results with experimentally recorded data has allowed a deeper insight into the peculiar features of the experiments and enabled a valuable code verification.

An overview is given on the preparation and characterization of hydroxyl terminated liquid polybutadienes and polyisoprenes which are potential alternative backbones for polyurethanes. After stating the requirements for such precursors, selected routes to their production are discussed, taken from more recent literature and from own experience. Characterization encompasses new methods of end group determination, problems of functionality and fractionation. In spite of the progress achieved in various aspects, outstanding properties of e.g. carbon black-filled polyurethanes have been reported rarely and on a larger scale commercial realization of such oligomers for high quality products seems somewhat uncertain at the moment. Ein Uberblick uber Darstellung und Charakterisierung von flussigen Polybutadienen und Polyisoprenen mit OH-Endgruppen wird gegeben. Derartige Telechele stellen mogliche Alternativbausteine fur Polyurethane dar. Zunachst werden die Voraussetzungen, die man an solche Vorprodukte stellen mus, zusammengefast. Danach werden ausgewahlte Darstellungswege aus der neueren Literatur und aus eigenen Erfahrungen diskutiert. Die Charakterisierung umfast neuere Methoden zur Endgruppenbestimmung sowie Probleme der Funktionalitatsermittlung und der Fraktionierung. Trotz des auf Teilgebieten erzielten Fortschritts werden hervorragende Eigenschaften, z. B. von rusverstarkten Polyurethanen nur selten berichtet, und der grostechnische Einsatz solcher Oligomerer fur Hochqualitatsprodukte erscheint zur Zeit noch etwas unsicher.

SBR latex was compounded with six different types of carbon black (SRF, FEF, HAF, SAF, HEB, and HCC-I) and vulcanization ingredients in aqueous dispersion by means of a dispersing agent. The particle size of the carbon black agglomerates in aqueous dispersion was estimated from turbidity and light scattering measurements. It was found that the size of the aggregates is by far larger than the average particle size of the SBR-latex used. The latex mixture containing carbon black and vulcanization ingredients was spray-dried to a fine-sized powder of an average particle size of 0.25 mm; this powder was subsequently vulcanized without the action of shear forces at a pressure of 200 bar. It was the aim of this study to answer the question whether latex-stage compounded vulcanizates can be reinforced without applying shear forces, if only the distribution of the carbon black in the compound is sufficiently good. The tensile strength was used for judging reinforcement; the quality of the carbon black dispersion was estimated by means of the Cabot rating method. The carbon black dispersion in the compounded powders proved to be excellent with fine-sized carbon blacks and was in the order of A 1 and B 2 of the Cabot scale. Scanning electron micrographs of the fracture zones and transmission electron micrographs on ultrathin cuts showed, however, differences in the microdispersion of the carbon blacks between powder-and mill-mixed compounds. A comparison of the mechanical properties of powder-and mill-mixed compounds yielded partially comparable tensile values for the powder compounds up to 20 MN/m2, but strikingly high hardness, elongation set and a pronounced stress-softening after repeated deformation (Mullins-effect).

The flow curves of SBR-1500 containing increasing amounts of tread powder and of glass powder of different grain sizes were taken by means of aGottfert High-Pressure-Capillary-Rheometer. Up to a certain extrusion pressure of about 300 bar the flow rate decreases with increasing filler concentration. In this pressure range the characteristic filler influence upon the flow behaviour was estimated from the relative viscosity.

In continuation of earlier studies the flow behaviour of mixtures of rubber (SBR, EPDM) and crumb from scrap tyre treads was estimated at 120°C with the aid of a high-pressure capillary rheometer. The influence of the capillary dimension on the flow curves was studied. With narrow and short capillaries the flow behaviour proved to be independent of the filler concentration. At low shear rates a discrimination of the flow characteristics according to the filler loading was observed only with capillaries above a certain width and length. At high shear rates with such a capillary an inversion of the rating of the flow curves was found.

Three carbon blacks of the SRF-, HEB- and HCC-1-type as well as powders from spray-dried mixtures of SBR-latex with these carbon blacks and of NBR-latex with HAF-black were subjected to high pressure up to 20 kbar.

The shear deformation which a rubber compound undergoes when passing through a mill nip was calculated. For this purpose the pressure distribution was measured using a strain gauge mounted in the table of a RAPRA micro-mill. The method has been applied to black-loaded master batches of natural rubber and styrene-butadiene rubber, where the shear deformation was estimated as a function of the mill nip opening. Furthermore, the physical properties of a latex-mixed powder vulcanizate was measured as a function of the estimated shear deformation.

ŜU2, a group of unitary operators isomorphic to the 2-dimensional unimodular unitary group, is the dynamical invariance group of the 2-dimensional harmonic oscillator. The corresponding group ring Open image in new window is used to classify completely the eigenfunctions, to represent arbitrary operators having nonvanishing matrix elements only within irreducible representations as unique functions of some special ring elements, and to construct general irreducible tensor operators whose matrix elements obey the known selection rules (Wigner-Eckhart theorem).

Es wird uber ein Mesverfahren zur kontinuierlichen Aufzeichnung des Quellungsverhaltens von Vulkanisaten berichtet, welches auf der Registrierung der Dickenanderung beruht, die eine Vulkanisatprobe wahrend der Quellung erfahrt. Das Messystem des Quelltesters steht hierbei in direktem mechanischen Kontakt mit der quellenden Probe.