Zum Quellverhalten duroplastischer Formstoffe

The Swelling Behaviour of Thermosetting Materials The moisture absorption of moulded materials can endanger a construction because of the change in volume of various parts. Therefore it is necessary to know the maximum possible swelling of the moulded materials employed at different relative humidities. The swelling of modified phenolic resin systems are described. Wood flour (which absorbs moisture) and powdered minerals (which in this case can be considered as inert) were used as fillers. Different methods have been developed to calculate the maximum possible swelling after a relatively short testing time (ca. 1000 h).     

Bleimennigeanstriche auf Aluminium- und Zinkoberflächen

Red Lead Coatings on Aluminium and Zinc Surfaces Theoretical considerations confirm the experience acquired in course of many years of practice that red lead, the well-known active pigment for the effective protection of steel, can be employed with advantage in corrosion protecting coatings for aluminium and zinc surfaces. The opinion found quite often in the literature and in advertisements, which assumes an incompatibility of lead-containing coatings on aluminium or zinc surfaces, owing to contact corrosion, is shown to be baseless and incorrect.     

Thermodynamic parameters of polystyrene solutions in cyclohexane,determined from sedimentation—diffusion equilibria in the ultracentrifuge. dependence on concentration,temperature and molecular weight

Determination of the sedimentation–diffusion equilibrium is one of the methods furnishing data on the thermodynamic parameters of polymer solutions. By means of this procedure measurements can be performed over a considerable range of concentrations. The equilibria in the ultracentrifuge have been determined for five polystyrene samples of narrow distribution covering the molecular weight range 2 × 10⁴ to 2 × 10⁶, at concentrations up to 40 wt-% and at temperatures of 30, 45 and 65 °C. The results are expressed in the data for the chemical potential of the solvent, the number-average chemical potential of the polymer and the interaction parameter ξ. The results are compared with those obtained from osmotic pressure, light scattering and critical miscibility measurements. At very low concentrations the molecular weight dependence of the interaction parameter is in agreement with literature values derived from osmotic pressure and light scattering figures. At higher concentrations this molecular-weight dependence decreases sharply but remains noticeable up to 40% concentration.     

Influence de l'addition d'ions etrangers sur la stabilite relative et la conductivite electrique des phases de type alumine β et β″

Addition of Pb²⁺ or Cd⁺² ions has an influence on the orientation of the preparation reaction for β and β″ alumina type phases. Variations in the relative stability of β and β″ phases are explained by the size of addition ions M⁺ or M²⁺. Variations of electrical conductivity are related to non-stoichiometric model with interstitial oxygen.     

Allgemeine Untersuchungsverfahren und Laboratoriumstechnik

Ohne Zusammenfassung     

The implementation of insertion and deletion algorithms for 1–2 brother trees

We derive an implementation in PASCAL of the insertion and deletion algorithms for 1–2 brother trees. The implementation is of interest not only in its own right but also in that it has given rise to an improved deletion algorithm.     

A Mathematical-Physical Model for the Charge Transport in p-Type SrTiO3 Ceramics Under dc Load: Maxwell-Wagner Relaxation

A mathematical-physical model to describe the current response of p-type SrTiO₃ ceramics in the low-temperature regime upon dc voltage step was developed, utilizing the numerical class library DIFFPACK (Numerical Objects, Norway). The current response in the time domain shows the experimentally observed Maxwell-Wagner relaxation (space charge polarization), followed by leakage current, and, eventually, resistance degradation. The relaxation behavior is analyzed by means of the simulation results for the spatial profiles of the electrical potential and the respective point defects. The impact of bias voltage and grain boundaries on the relaxation time is investigated. The simulation results are compared with experimental data.