Measuring the friction coefficient in the case of plastification of metals by elastomers

The friction measuring apparatus according to O. Pawelski, which is based on the strip drawing experiment, is used to determine friction coefficients in plastic shaping of metals. By implementing elastomer inlays into the drawing cheeks the same principle has been applied to the contact between metals and elastomeric media. The plastification of metal by the extremely shear-weak elastomer is possible, because it is completely constrained with metal, so that a sufficiently high hydrostatic pressure in the inlay is generated. Elementary theory in combination with FEM showed that the friction coefficient, calculated using only the global static equilibrium of forces, is in very good approximation with simply the mixture of the friction coefficient between metal strip and elastomer and the friction coefficient between metal strip and drawing cheek weighted with the corresponding contact areas. Drawing experiments with aluminium 99.5 or steel St 37 and polyurethane or soft rubber were carried out. The important influence of lubrication and roughness of the metal strip on the friction coefficient was investigated.     

Verhalten des Stahles X 6 CrNi 18 11 unter kombinierter Kriech- und Wechselbeanspruchung bei 823 K

Experimentelle Untersuchung des Kriech- und Wechseldehnverhaltens des austenitischen Stahles X 6 CrNi 18 11 (Werkstoffnummer 1.4948) bei Beanspruchung durch Kriechen und Ermüden. Auswertung der Ergebnisse unter Anwendung der linearen Schadensregel. Vergleich mit Auslegungskriterien nach dem ASME BPVC.     

Polystyrene-supported acid catalysis

The present state of polymer-supported acid catalysis is considered. Models describing the catalytic action of gel-like and macroporous resin catalysts are presented. By chemical modification of poly (styrene-co-divinylbenzene) matrices, e.g. different ways of sulphonation, nitration, chlorination, fluorination and sulphoalkylation, the activity/selectivity and thermal stability of sulphonic acid resin catalysts can be improved. The synthesis of polymer-supported Lewis acids is described. By comparison to AlCl₃ higher catalytic activities are obtained with the use of AlBr₃.     

Occurrence of Ti3+ and Fe2+ in Mullite

Electron paramagnetic studies showed that Ti³⁺ and Fe²⁺ occur in mullites taken from a refractory material which was fused-cast under a reducing atmosphere. Exposure of the mullite samples to temperatures >1600°C caused oxidation of Ti³⁺ and Fe²⁺ to Ti⁴⁺ and Fe³⁺, respectively.     

Comparison of different techniques for the observation of the lamellar texture of isotactic polypropylene: TEM of surface replicas,TEM after staining,and SFM

Summary In the present study three different techniques have been employed to observe the lamellar texture of isotactic polypropylene (iPP) crystallized from the melt under the influence of shearing: (a) Transmission electron microscopy (TEM) of surface replicas of permanganically etched samples (b) TEM of thin sections of Ruthenium-oxide stained samples and (c) Scanning force microscopy (SFM) in contact mode of permanganically etched samples. The aim was to assess their relative merits in terms of practicability, resolution and type of information.     

Organische und anorganische Ionenaustauscher zur heterogen katalysierten Alkylierung von Aromaten

Organic and inorganic ion exchangers as catalysts for the heterogeneous alkylation of aromatics . Ion exchangers has advantages over low molecular for use in industrial alkylation reactions. The reactivity and selectivity behaviour of the polymeric catalysts were found to be markedly influenced by the structure of the polymeric matrix as well as the type and number of the functional groups. In this connection many similarities between inorganic ion exchangers (zeolites) and organic ion exchange resins were detected.