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- FTIR spectroscopy (14) (entfernen)
Organisationseinheit der BAM
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- 1.8 Umweltanalytik (1)
- 4 Material und Umwelt (1)
- 4.5 Kunst- und Kulturgutanalyse (1)
- 6 Materialchemie (1)
- 6.6 Physik und chemische Analytik der Polymere (1)
- 7.1 Baustoffe (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
Eingeladener Vortrag
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Although fire safety regulations for buses have been adapted in recent years regarding, for example, fire detection and engine fire suppression systems, the changes in regulations for bus interior materials are minimal. A comparison of fire safety regulations for interior materials in other transport sectors for trains, ships or aircraft reveals a much lower level of requirements for bus materials. Although repeated bus accidents as well as fire statistics show the danger a bus fire can pose to passengers.
In particular, the combination of a fire incident and passengers with reduced mobility led to severe disasters in Germany and other European countries. To enhance the fire safety for passengers, the interior bus materials are crucial as the fire development in the bus cabin determines whether escape and rescue is possible. Against this background, bus interior materials were tested in different fire test scenarios. Measurement of a wide variety of parameters, for example, the mass loss, ignition time, smoke gas composition, heat release rate among others were carried out. Tested materials complied to the newest set of requirements. For this purpose, interior materials and their components had to be identified according to their chemical structure. Parts of the tests were funded by BASt (Federal Highway Research Institute) in the project 82.0723/2018. Experimental results show reaction-to-fire behaviour which lead to very limited times for escape and rescue in case of fire in a bus cabin. Based on the studies on fire behaviour and toxicity assessment, recommendations for improved fire safety regulations for interior materials could be made.
Reclaimed asphalt pavements (RAP) with increased contents of polycyclic aromatic hydrocarbons (PAH) are restricted for reuse due to their harmful effects on humans and the environment. This work investigated whether Fourier transform infrared (FTIR) spectroscopy is suitable for a fast and simple identification and quantification of PAH in binders recovered from reclaimed asphalts. For this, the binders from 34 RAP samples were recovered using a rapid procedure developed at the Universität Kassel and were examined with infrared spectroscopy. The obtained spectra were pre-processed (Standard Normal Variate transformation, 1st derivative) and evaluated using a combination of factor analysis and linear discriminant analysis. The results showed that various PAH groups with differently pronounced aromatic structures are present in the binders.
However, with FTIR spectroscopy combined with the multivariate methods, a statistical model was developed allowing for the differentiation between the PAH groups and also for the distinction between PAH contents below or above the threshold of 25 mg/kg valid in Germany.
This talk will be divided into two parts. In the first part I will present the analytical techniques and the equipment used by the Centre for the Study of Manuscript Cultures that can be applied for the study of decorated papers. The analyses aim to determine the constituent materials of papers, pigments, dyes and metals and the techniques used for their production. I will focus in particular on the kind of information these techniques allow us to gather: through optical microscopy we conduct fibre analysis in order to identify the plant used as raw material in paper production while Reflectography, X-Ray Fluorescence and InfraRed, Raman and Visible Reflectance Spectroscopy are used to study the sizing agents, the pigments, dyes and metals. In the second part I will show some results obtained by the application of these techniques on a few Persianate manuscripts, dating between the 15th and 17th centuries, belonging to the corpus of Ilse Sturkenboom.
Water as side effect of reinforcing boehmite filler Local changes in anhydride cured epoxy resin
(2019)
Nanocomposites offer wide opportunities for lightweight constructions and enable reduction of weight and volume. Beside macroscopic toughening nanoparticle reinforced polymers show a soft interface around boehmite (AlOOH) filler nanoparticles. A related strong interaction between boehmite and the anhydride cured resin system is widely suspected in literature but not determined by structural Analysis. Determination of the molecular structure is important to allow simulations approaching the real system and predict future reinforcing effects.
DRIFT (diffuse refletance infrared fourier transformed) spectra of the boehmite reinforced anhydride cured epoxy show significant changes in the molecular structure compared to the neat polymer. Further investigations of the interactions between the single components of the resin system and the boehmite filler pointed out reactions between released water released from the boehmite filler and the anhydride hardener or amine accelerator. This leads to the discussion of competing polymerisation mechanisms that highly influence the polymer properties. Ongoing experiments and literature research approve that this impact of water is able to locally change the stoichiometrie, alter the curing mechanism or support an inhomogeneous crosslink density.
The aim of this study was to identify specific chemical bonds and characteristic structures in melanoidins formed from D-glucose and L-alanine between 130 and 200 °C. The results might be used to control the type and amount of melanoidin produced during food processing. For this purpose, complementary techniques, such as FTIR, NMR, EPR, and MALDI-ToF, were employed. At 160 °C color, solubility and UV/Vis absorption change characteristically and consequently, structural transformations could be observed in FTIR and NMR spectra. For example, sharp signals of N-H, C-N, and C-H oscillations in the L-alanine spectrum are prone to inhomogeneous broadening in melanoidins prepared above 150 °C. These changes are caused due to formation of heterogeneous macromolecular structures and occur during condensation reactions that lead to an increasing loss of water from the melanoidins with increasing temperatures. Additionally, MALDI-ToF-MS indicates the polymerization of glyoxal/glyoxylic acid and EPR shows the formation of radical structures.
The hazards for passengers during vehicle fires result from the increasing temperature and the emitted smoke gases. A fire was set on a car to investigate the development of temperature and of gaseous fire products in the passenger compartment. The study was based on a full-scale test with a reconstructed scene of a serious car fire. The aim of this work was to identify the conditions for self-rescuing of passengers during a car fire.
A dummy, equipped with several thermocouples, was placed on the driver’s seat. Also, the smoke gases were continuously collected through a removable probe sensor corresponding to the nose of the dummy in the passenger compartment and analyzed using Fourier transform infrared spectroscopy. Additionally, several car components were investigated in the smoke density chamber (smoke emission and smoke gas composition). It was found that the toxic gases already reached hazardous levels by 5 min, while the temperatures at the dummy were at that time less than 80 °C. The toxicity of smoke gases was assessed using the
fractional effective dose concept. The various experimentally parameters (temperature and smoke gas composition) were implemented into numerical simulations with fire dynamics simulator. Both the experimental data and the numerical simulations are presented and discussed.
Structural properties of iron-phosphate glasses: spectroscopic studies and ab initio simulations
(2014)
Vitrification is the most effective method for the immobilization of hazardous waste by incorporating toxic elements into a glass structure. Iron phosphate glasses are presently being considered as matrices for the storage of radioactive waste, even of those which cannot be vitrified using conventional borosilicate waste glass. In this study, a structural model of 60P2O5–40Fe2O3 glass is proposed. The model is based on the crystal structure of FePO4 which is composed of [FeO4][PO4] tetrahedral rings. The rings are optimized using the DFT method and the obtained theoretical FTIR and Raman spectra are being compared with their experimental counterparts. Moreover, the proposed model is in very good agreement with X-ray absorption fine structure spectroscopy (XANES/EXAFS) and Mössbauer spectroscopy measurements. According to the calculations the Fe3+ is in tetrahedral and five-fold coordination. The maximal predicted load of waste constituents into the glass without rebuilding of the structure is 30 mol%. Below this content, waste constituents balance the charge of [FeO4]- tetrahedra which leads to their strong bonding to the glass resulting in an increase of the chemical durability, transformation and melting temperatures and density.
For many years after the discovery of the Dead Sea Scrolls, text analysis and fragment attribution were the main concern of the scholars dealing with them. The uncertain archaeological provenance of a large part of the collection added difficulties to the already formidable task of sorting thousands of fragments. After 60 years of scholarly research the questions of origin, archaeological provenance and correct attribution of the fragments are still debated. To help address these questions we have developed a methodology suitable for the material studies of the scrolls using combinations of X-ray, FTIR and Raman techniques. On the one hand, an accurate characterization of the highly heterogeneous writing media of the Dead Sea Scrolls leads to a reliable reconstruction of their history and, thus, contributes significantly to the current debate. On the other hand, it provides new information on the production of ancient parchment towards the end of the Second Temple period, opening a new page in the historical study of technology.
Chemical-analytical investigation of fire products in intermediate storages of recycling materials
(2012)
Organic materials like paper, cardboard, textiles or plastics are mostly flammable. In intermediate storages for recycling products, these materials are stored in large amounts. If fire occurs in these stores, large emissions of smoke and other potentially harmful products are likely. In the present study, the gaseous products released from fires of such materials—for example, because of self-ignition—were investigated. Different fractions (paper/cardboard, textiles and plastics) were crushed at low temperatures (about 80 K) and subsequently allowed to smoulder at different temperatures using the German standard Deutsches Institut für Normung 53436. The gases produced were sampled and analysed using Fourier transform infrared spectroscopy. The chemical composition of these gases differed considerably depending on fuel type. For flammable materials without heteroatom, the gases consisted predominantly of toxic compounds like carbon monoxide and carbon dioxide. Smouldering of materials containing heteroatoms showed, in addition to carbon monoxide, carbon dioxide and water vapour, further toxic components containing the heteroatom. Materials containing chlorine produced hydrogen chloride, and materials containing nitrogen produced ammonia and hydrogen cyanide.
Fires on waste dumps, surface landfills, Underground stowing or storage facilities of Recycling factories may have multiple harmful effects on individuals on site and on environment.
Possibly several tens of thousands of tons flare up plunging vast areas in smoke and releasing large amounts of flue gases. Experience shows that fire fighting takes days or even weeks and moreover, as long as hidden glowing nests exist fires may break out repeatedly weeks or months later. In the light of this, fire prevention is much easier to manage than extinction. It is of internst to identify the geometrical and physical conditions under which the mid-term or long-term storage of recycling materials can be performed avoiding self-ignition. Our Guideline presents a novel method developed at BAM which combines experimental tests on lab-scale with numerical simulations in Order to obtain permissible geometries of deposits and storage times at which self-ignition can be certainly avoided (Berger 2010).