TY - GEN A1 - Boyadzhiev, Marin A1 - Langenstraßen, Rainer A1 - Evtimova, Rozeta A1 - Nenkova, Sanchi A1 - Behrendt, Gerhard T1 - Development of Branched Aromatic Polyester Polyols from PET T2 - Wissenschaftliche Beiträge 2007 N2 - Diese Arbeit befasst sich mit einer neuen Klasse verzweigter aromatischer Polyesterpolyole (APP), die auf PET-Abfällen basieren und für die Herstellung hochwertiger Polyurethane entwickelt wurden. Dieses Ziel wurde durch eine modifizierte Umesterung von PET durch eine Glykolmischung mit einem geringen Anteil Triolen erreicht. Es wurde eine Reihe verzweigter APP mit Hydroxylzahlen im Bereich von 260 bis 380 mg KOH/g und Hydroxyl-Funktionalitäten zwischen 2,00 und 2,30 erhalten. Die Viskosität der Produkte steigt im Bereich der Funktionalität von 2,03 bis 2,12 geringfügig und darüber stärker an. Für jede Reihe der APP mit Hydroxylzahlen von 260, 320 bzw. 380 mg KOH/g wurde bezüglich der Viskosität, der Langzeitstabilität und der Hydroxyl-Funktionalität ein Eigenschaftsoptimum gefunden. APP mit höherer Hydroxyl-Funktionalität können zur Herstellung von Polyurethan-Gießharzen und jene mit niedrigeren Hydroxylzahlen für Beschichtungen, z. B. von Leder, verwendet werden. N2 - 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. KW - Aromatische Polyesterpolyole KW - PET-Abfall KW - APP Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus-389 SN - 0949-8214 VL - 12 SP - 11 EP - 16 ER - TY - JOUR A1 - Rangelova, Nadezhda A1 - Radev, Lachezar A1 - Nenkova, Sanchi A1 - Salvado, Isabel Miranda A1 - Vas Fernandes, Maria A1 - Herzog, Michael T1 - Methylcellulose/SiO2 hybrids: sol-gel preparation and characterization by XRD, FTIR and AFM JF - Central European Journal of Chemistry N2 - 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. Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9636 SN - 2391-5420 VL - 9 IS - 1 SP - 112 EP - 118 ER - TY - JOUR A1 - Tsonev, Tsvetomir A1 - Herzog, Michael A1 - Nenkova, Sanchi T1 - Shape memory polyurethanes based on recycled polyvinyl butyral. I. Synthesis and morphology JF - Central European Journal of Chemistry N2 - 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. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9664 SN - 2391-5420 VL - 11 IS - 12 SP - 2058 EP - 2065 ER - TY - JOUR A1 - Dimitrov, Kiril A1 - Herzog, Michael A1 - Nenkova, Sanchi T1 - Fe3O4 Modification of Microcrystalline Cellulose for Composite Materials JF - American Journal of Chemistry N2 - 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. KW - microcrystalline cellulose KW - magnetite KW - SEM KW - XRD Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9651 SN - 2165-8781 VL - 3 IS - 5 SP - 140 EP - 147 ER -