Struktur und Eigenschaften von ABS-Polymeren. IV. Zum Einfluß der thermischen Vorbehandlung auf das Deformationsverhalten von ABS-Pfropfpolymerisaten

The influence of thermal history on the thermomechanical properties of a graft polymer (ABS) is investigated. The thermal pretreatments are: sharp quenching from above the glas-transition of the matrix resin, annealing below the glas transition. A first characterization of the influence of these two pretreatments is done by measuring density, probe length as function of temperature and by DTA. The less modulus in the region below the glas transition of the matrix resin is very sensitive to thermal pretreatment. Small but reproducible influences are observed in the glas transition region of the polybutadien particles. At room temperature stress-strain measurements are achieved until fracture happens. Crazing is observed (which is often called stress-whitening) in all cases, but the extent of craze growing is dependent on thermal history. The measurements are completed by scanning micrographs of the fracture surfaces. Annealing of the fracture surfaces gives additional informations. The results are discussed using the concept of free volume which is variated by thermal pretreatment. At room temperature the phase-boundary between polybutadion particle and matrix resin is considered as transition zone from high to small hole concentration. The sharpness of this zone is supposed to be a decisive parameter for the macroscopic deformation behaviour.     

Thermochemical production of hydrogen by a vanadium/chlorine cycle. Part 2: Experimental investigation of the individual reactions

Chemical engineering aspects and the chemical practicability of a vanadium/chlorine hydrogen-producing cycle were investigated on a laboratory scale. The most significant results are presented and discussed. The total process was balanced and optimized using the experimental results as the basis. The overall thermal efficiency was calculated to be 42.5% (see Part 1).     

Über die Streuung des Fettgehaltes verschiedener Ölpflanzen I: Winterraps und Sonnenblume

Deviation in Fat Content of Different Oil Yielding Plants To get an insight into the factors and their intensity causing deviation in the oil content of some of the oil yielding plants, the deviating components of winter rape, sunflower, linseed, soybean and mustard species were determined with the help of variance analysis, carried out in widely different experiments with cultivated material as well as in value and control tests. The greatly varying extreme values of the fat content resulted from environmental factors, yearly and local effects as well as genetically dependent family and species differences. The standard deviations show quite clearly that the effects of year, location and species are different in different oil yielding plants.     

The effect of chemical-vapor-deposition conditions on the properties of carbon-carbon composites

Properties are given for as-deposited and heat-treated carbon-felt, carbon-matrix composites infiltrated at deposition temperatures of 1100 and 1400°C, and pressures of 20 and 630 Torr. A thermal stress figure of merit was calculated for each material, with the heat-treated composite infiltrated at 1400°C and 630 Torr yielding the highest value. As with most graphitizing carbon materials, heat-treatment resulted in a decrease of the flexural strengths and moduli. The strength-to-modulus ratios, however, increased, being highest for deposition conditions of 1400°C and 630 Torr. Heat-treatment also resulted in an increase in thermal conductivity and a decrease in thermal expansion. These changes were related to the degree of crystallinity and to the formation of cracks within the matrix.