540 Chemie und zugeordnete Wissenschaften
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- APP (1)
- Aromatische Polyesterpolyole (1)
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- PET-Abfall (1)
- Polyesterpolyole (1)
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Shape memory polyurethanes (SMPUs) were synthesized by 4,4′-diphenylmethane diisocyanate (MDI), hexane-1,6-diol (HD), polypropylene glycol (PPG), and recycled polyvinyl butyral (PVB). Dynamic mechanical analysis, differential scanning calorimetry and Fourier transformation infrared attenuated total reflection spectroscopy was used to characterize the poly (vinylbutyral-urethanes). Micro-phase domain separation of hard and soft segments and phase inversion were investigated. Increasing the hard segment content, i.e., average hard segment molecular weight, leads to an increase in the degree of micro-phase separation, hard domain order and crystallinity. The crystalline hard segment structures combined with the elastic nature of soft segment matrix provide enough physical and chemical crosslinks to have shape memory effect.
A new synthesis method for producing cellulose ferrite micro- and nano- composites was developed and new material properties were studied. Microcrystalline cellulose was modified with a mixture of Fe+2/Fe+3 to produce surface bonded nanoparticles magnetite (Fe3O4). Optimal conditions were determined. Microsized hematite (Fe2O3) was mixed with microcrystalline cellulose and used as a reference. The magnetite modified microcrystalline cellulose and hematite filled microcrystalline cellulose were used together with polyurethane prepolymer. New composite crosslinked conductivity materials based on the magnetite modified microcrystalline or hematite filled microcrystalline cellulose and polyurethane were developed. Morphology, crystalline properties, water absorption and electro conductivity of these materials were characterized. The physical properties of these materials were characterized by different analytical methods: SEM, XRD, water absorption and electrical resistance.
Methylcellulose (MC) / SiO2 organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content.
Several mutation positions have been chosen for introducing positively charged lysines in human cytochrome c (cyt c) with the aim of increasing the reaction rate with superoxide radicals (SO) and thus, the sensitivity of an electrochemical cyt c based SO biosensor. The impact of the mutations on structural and redox properties as well as on the reaction rate with SO are verified. Four mutants show a higher reaction rate with the radical compared to the wild type. These mutants are used for the construction of SO sensors based on thiol-modified gold electrodes and covalently fixed proteins. The E66K mutant electrode has a clearly higher sensitivity in comparison to the wildtype based sensor.
An oxygen reducing electrode made of bilirubin oxidase and multi-walled carbon nanotubes (BOD-MWCNT-Au electrode) is coupled to enzymes catalysing oxygen-consuming reactions such as glucose oxidase (GOD) to result in a membrane-free bienzyme electrode. The feasibility of such a molecularly assembled system stabilized by covalent linkage has been demonstrated. The electrochemical characterisation of the bienzyme electrode reveals sensitivity to the enzyme substrate. The results indicate that the BOD-electrode provides a suitable platform for sensing analytes for which oxidases of high activity are available.
Presently, about 8 million metric tons of polyurethanes are produced in the world annually. During production of precursors, semi-finished products and final products about 5 to 10 % of this amount is waste, i. e. an amount of about half a million tons. To this add the products after their life cycle. This is a large source of material which should not be given to landfills or incinerators but be used as secondary materials for the production of new polyurethanes.
Nanostructured ferritic oxide dispersion strengthened (ODS) alloy is an ideal candidate for fission/fusion power plant materials, particularly in the use of a first-wall and blanket structure of a next generation reactor. These steels usually contain a high density of Y-Al-O nanoparticles, high dislocation densities and fine grains. The material contains nanoparticles with an average diameter of 21 nm. Irradiation of these alloys was performed with a dual beam irradiation of 2.5 MeV Fe+/31 dpa and 350 keV He+/18 appm/dpa. Irradiation causes atomic displacements resulting in vacancy and self-interstitial lattice defects and dislocation loops. Additionally to structural changes, the effect of the irradiation generated defects on the mechanical properties of the ODS is investigated by nanoindentation. A clear hardness increase in the irradiated area is observed, which reaches a maximum at a close surface region. This feature is attributed to synergistic effects between the displacement damage and He implantation resulting in He filled vacancies
The synthesis of polyurea dispersion polyols (PHD) was developed using a new route via depolymerization of polyurethane polyureas by a mixture of at least two glycols in the presence of a consumable catalyst, i. e. a secondary aliphatic amine. On this way such polyols were produced with a particle size distribution with a maximum in the 120 to 400 nanometer region with hydroxyl numbers of 180 to 300 mg KOH/g being optically clear and highly reactive. The exact adjustment of the ethylene oxide content of the reaction mixture together with that of the polyether polyol originally present in the polyurethane polyurea used in a predetermined range of surface tension as well as specific reaction conditions leads to these polyols which will give in turn polyurethanes with exceptional properties.
This paper is directed to the development of a new type of branched aromatic polyester polyols (APP) based on PET wastes designed to produce high quality polyurethanes (PUR). To this end, a modifi ed transesterification of PET by a glycol mixture was used and simultaneously small amounts of triols were incorporated into the reaction mixture. By this method, a series of branched APP’s with hydroxyl numbers in the range of 260 to 380 mg KOH/g and hydroxyl functionalities between 2.00 and 2.30 was received. The viscosity of the products increased slowly with the functionality in the range of 2.03 to 2.12 and sharper beyond this value. An optimum of properties was found in each series of APP with hydroxyl numbers of 260, 320, and 380 mg KOH/g, resp. with respect of viscosity, long term stability and hydroxyl functionality. APP with a higher hydroxyl functionality are useful to produce cast polyurethane resins, those with lower hydroxyl numbers for coatings, e. g. of leather.
Diese Arbeit hat die Entwicklung einer Anlage zum Ziel, mit der aus festem Polyethylenterephthalat (PET), wie es als Produktionsabfall bei seiner Herstellung und Verarbeitung entsteht, durch Umesterungen in Gegenwart von Glykolen und/oder oligomeren Estern Aromatische Polyesterpolyole (APP) als Rohstoffe für Polyurethane kontinuierlich hergestellt werden können. Die Arbeit baut auf den bisherigen Entwicklungen zur diskontinuierlichen Herstellung von Recyclingpolyolen aus PET-Abfällen an der Technischen Fachhochschule Wildau auf. Mit Hilfe dieses Verfahrens können Polyesterpolyole verschiedener Eigenschaften für unterschiedliche Einsatzgebiete, z. B. Polyurethan-Hartschaumstoffe, -Beschichtungen, -Vergussmassen etc., hergestellt werden, die nur durch Modifizierungen in der Menge der Ausgangsstoffe und der Verfahrensbedingungen an die Erfordernisse angepasst werden. Dieses Verfahren liefert im diskontinuierlichen Betrieb qualitativ hochwertige Polyesteralkohole in einem breiten Parameterbereich. Auf Grund des hohen Aromatenanteils besitzen sie einen inhärenten Flammschutz. Über Grundlagenuntersuchungen zum Lösevorgang von PET in verschiedenen Lösungsmitteln unter thermischer und mechanischer Beanspruchung und zur Umesterung der PET-Lösung zu oligomeren Produkten unter diskontinuierlichen Laborbedingungen, die auf einer Miniplantanlage ausgeführt wurden, ist bereits berichtet worden. Aufbauend auf diesen Ergebnissen soll eine kontinuierlich arbeitende Anlage konstruiert und gebaut werden, die zur Bestimmung der Verfahrensparameter der kontinuierlichen Glykolyse von PET dient. Die in dieser Arbeit ermittelten verfahrenstechnischen und konstruktiven Grundlagen stellen die Basis zur Maßstabsvergrößerung für die Konstruktion und den Bau größerer Anlagen, einer Technikums- und darauf aufbauend einer Pilotanlage, dar. Für ein kontinuierliches Verfahren zur Herstellung von Polyesterpolyolen aus PET gibt es weltweit kein Beispiel und auch keine geschützte Lösung, so dass mit dieser Arbeit wissenschaftliches und technisches Neuland betreten wird. Das rohstoffliche Recycling der PET-Abfälle ist bisher nur diskontinuierlich durchgeführt worden. Das diskontinuierliche Verfahren hat jedoch eine Reihe von Nachteilen, die vor allem in der langen Lösephase für das PET im Glykolyse-Gemisch, in längeren Reaktionszeiten, in den schwankenden Parametern der Produkte sowie in der zu geringen Wirtschaftlichkeit begründet liegen. Ein kontinuierliches Verfahren hätte demgegenüber die Vorteile einer konstanten Produktqualität und einer verbesserten Wirtschaftlichkeit. Nach eigenen Kostenabschätzungen gewinnt ein kontinuierliches Verfahren bei einem Durchsatz von mehr als etwa 1000 t/a an Wirtschaftlichkeit gegenüber einer diskontinuierlichen Verfahrensweise, da dann die Vorteile des kontinuierlichen Verfahrens (geringere Personalkosten, gleichbleibende Produktqualität) die Nachteile (höhere Investitionskosten, höherer Energiebedarf) überwiegen.