Schrifttumsberichte

Ohne Zusammenfassung     

Parallel integration of aligned carbon strings in polymer composite: Dielectrophoretic preparation,finite element simulation,and electrical characterization

We report on dielectrophoretic alignment of carbon black particles into radially arranged string‐like assemblies in oligourethane mixtures followed by photopolymerization. Using finite element modelling and optical microscopy we find significant difference in field distributions depending on the substrate beneath aligned films. On glass, the field is concentrated between the electrode tips leading to string‐like assemblies between the tips. On oxide covered silicon, the field is distributed along the electrode circumference leading to more distributed fractal assemblies. Using comprehensive dc resistance measurements and ac‐impedance spectroscopy we show that the resistance of the strings varies from 120 kΩ to 5 MΩ with a mean of 1.03 MΩ. Strings on oxide covered silicon show significantly higher resistances than the strings on glass. We also demonstrate the effect of aging and an increase in resistance through elongating aligned strings. POLYM. COMPOS., 36:1866–1874, 2015. © 2014 Society of Plastics Engineers     

Vorstellung eines Leitfadens zum Evaluieren der hygienegerechten konstruktiven Ausführung von Süßwarenmaschinen

Consumer protection is one of the most important criteria within industrial food production. The Machinery Directive and DIN EN 1672-2:2021-05 contain general requirements for hygienic design and cleanability of food processing machinery. Nevertheless, it happens that machines or equipment parts are used that are not suitable for the products to be processed. The consequences of this go as far as a public recall of products with a corresponding damage to the image of the food manufacturer. The working group of machine manufacturers and confectionery companies in the IVLV has dealt with the problem at the level of the association within the framework of a pre-competitive exchange and has developed a guideline for action as well as supporting forms for the procurement process of confectionery machines from the point of view of hygiene.     

Analytical determination of compounds released during pyrolysis,smoldering, and combustion experiments with insulation materials from renewable resources

Obviously, the use of insulation materials from renewable resources in buildings could provide benefits regarding environmental protection and sustainable management. Nevertheless, their market share in Germany is estimated to be about 7% because of a partial lack of knowledge about their properties, and therefore, of construction certifications. This work was intended to close a knowledge gap concerning emissions during pyrolysis, smoldering, and combustion of commercial insulating materials made from wood, cellulose, meadow grass, hemp, jute, cork, and seaweed as well as polystyrene for comparison reasons. Laboratory-scale experiments were conducted and the measurement of thermal decomposition products was done with gas chromatography combined with mass spectrometry (GC/MS). It was realized that almost all the products could be assigned to the following eight substance classes: carbohydrates, aldehydes/ketones, carbonic acids/esters, substituted phenols, furans, aliphatic hydrocarbons, substituted benzenes, and polycyclic aromatic hydrocarbons. Substance spectra were generated that showed certain conformities, especially between the insulating materials made from wood, cellulose, and meadow grass as well as hemp and jute. Comparisons of the sum of peak areas in the GC/MS-chromatograms provided indications of the relative extent of thermal decomposition product emissions. Calculations according to (∑peak areas _{renewable material})/(∑peak areas _polystyrene) revealed factors between 0.18 (wood, cork) and 0.028 (meadow grass). In the thermal emissions, defined hazardous substances or substance groups were frequently measured. These were included in a toxicity evaluation by which, inter alia, advantages of the natural products compared to polystyrene could be demonstrated.     

Vergleich verschiedener Ansätze zur nachhaltigen Olefinproduktion nach dem MtO- und FT-Verfahren

Olefins are an irreplaceable part of modern organic chemistry. According to the current state of the art, mostly crude oil is used as raw material, which is separated in a refinery. The naphtha fraction is then fed into a steam cracker, in which the hydrocarbons are cracked to the desired olefins. In this short communication, two alternative production processes are compared as a basis for alternative routes to the production of olefins.     

Growth of 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) I. Anisotropic thermal expansion

Expansion of TATB is studied on a molecular level by means of x-ray crystallography. Continuous monitoring of the cell constants of TATB between 214 K and 377 K allows calculation of a volume change of +5.1% for this molecular system. Expansion of the pure material is almost exclusively a function of a 4% linear increase in the c axis (the perpendicular distance between sheets of hydrogen-bonded TATB). Calculated from these data, the volume coefficient of thermal expansion for crystalline TATB is 30.4 × 10⁻⁵ K⁻¹. The structural features of crystalline TATB and its anisotropic thermal-expansion behaviour are compared with those of graphite and boron nitride. Two other crystalline products in the bulk TATB are either actual polymorphs of TATB or impurities.