@misc{BoyadzhievLangenstrassenEvtimovaetal.2007, author = {Boyadzhiev, Marin and Langenstraßen, Rainer and Evtimova, Rozeta and Nenkova, Sanchi and Behrendt, Gerhard}, title = {Development of Branched Aromatic Polyester Polyols from PET}, series = {Wissenschaftliche Beitr{\"a}ge 2007}, volume = {12}, journal = {Wissenschaftliche Beitr{\"a}ge 2007}, issn = {0949-8214}, doi = {10.15771/0949-8214_2007_1_2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-389}, pages = {11 -- 16}, year = {2007}, abstract = {Diese Arbeit befasst sich mit einer neuen Klasse verzweigter aromatischer Polyesterpolyole (APP), die auf PET-Abf{\"a}llen basieren und f{\"u}r 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-Funktionalit{\"a}ten zwischen 2,00 und 2,30 erhalten. Die Viskosit{\"a}t der Produkte steigt im Bereich der Funktionalit{\"a}t von 2,03 bis 2,12 geringf{\"u}gig und dar{\"u}ber st{\"a}rker an. F{\"u}r jede Reihe der APP mit Hydroxylzahlen von 260, 320 bzw. 380 mg KOH/g wurde bez{\"u}glich der Viskosit{\"a}t, der Langzeitstabilit{\"a}t und der Hydroxyl-Funktionalit{\"a}t ein Eigenschaftsoptimum gefunden. APP mit h{\"o}herer Hydroxyl-Funktionalit{\"a}t k{\"o}nnen zur Herstellung von Polyurethan-Gießharzen und jene mit niedrigeren Hydroxylzahlen f{\"u}r Beschichtungen, z. B. von Leder, verwendet werden.}, language = {en} } @misc{PeshkovBehrendtEvtimovaetal.2012, author = {Peshkov, Vladimir and Behrendt, Gerhard and Evtimova, Rozeta and Herzog, Michael}, title = {New Polyurethanes with a polyurea matrix}, series = {Wissenschaftliche Beitr{\"a}ge 2012}, volume = {16}, journal = {Wissenschaftliche Beitr{\"a}ge 2012}, issn = {0949-8214}, doi = {10.15771/0949-8214_2012_1_12}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-1259}, pages = {93 -- 102}, year = {2012}, abstract = {Based on a previously published (Peshkov 2011) synthesis route of nanoscale oligourea dispersion polyols (NODP) a new type of polyurethanes with a polyurea matrix was developed. Polyurethanes with high hardness and elasticity were prepared by reacting a formulation based on the NODP's and di- or polyisocyanates. The polyurethanes obtained as films were characterised by mechanical tests and dynamic mechanical analysis (DMA). The phase structure depends on the amount of nanoparticles present, the isocyanate index, and the mode of curing. It is suggested that nanoparticles have to be of similar size as the matrix into which they are embedded to show a typical nano- effect such as shown here. These elastic polymers show an unusual high Shore D hardness of some 70 and tensile strength up to 47 MPa at elongations at break of 7 \%.}, language = {en} } @misc{PeshkovEvtimovaHerzogetal.2011, author = {Peshkov, Vladimir and Evtimova, Rozeta and Herzog, Michael and Behrendt, Gerhard}, title = {New Synthesis Route for PHD Polyols}, series = {Wissenschaftliche Beitr{\"a}ge 2011}, volume = {15}, journal = {Wissenschaftliche Beitr{\"a}ge 2011}, issn = {0949-8214}, doi = {10.15771/0949-8214_2011_1_9}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-1105}, pages = {67 -- 72}, year = {2011}, abstract = {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.}, language = {en} } @misc{EvtimovaLozevaSchmidtetal.2003, author = {Evtimova, Rozeta and Lozeva, Yordanka and Schmidt, Karl-Heinz and Wotzka, Michael and Wagner, Peter and Behrendt, Gerhard}, title = {Polyester Polyols from Waste PET Bottles for Polyurethane Rigid Foams}, series = {Wissenschaftliche Beitr{\"a}ge 2003}, volume = {8}, journal = {Wissenschaftliche Beitr{\"a}ge 2003}, issn = {0949-8214}, doi = {10.15771/0949-8214_2003_1_4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-3795}, pages = {19 -- 25}, year = {2003}, abstract = {This paper describes a modified process to produce polyester polyols from PET wastes derived from the "bottle fraction residue" of the German Dual System (DSD) [11] employing a waste oligoester condensate of the polyesterification process with the addition of some glycols of longer chain and occasional modification with further dicarboxylic acids to produce polyester polyols of a broad range of properties which are further reacted to form polyurethane or polyisocyanurate rigid foams for insulation, construction materials, or coatings.}, language = {en} } @misc{BelkeEvtimovaLangenstrassenetal.2004, author = {Belke, Martin and Evtimova, Rozeta and Langenstraßen, Rainer and Pniok, Iris and Peshkov, Vladimir and Behrendt, Gerhard}, title = {Closed Loop of Polyurethane Flexible Slabstock Foam Wastes by a Chemical Process}, series = {Wissenschaftliche Beitr{\"a}ge 2004}, volume = {9}, journal = {Wissenschaftliche Beitr{\"a}ge 2004}, issn = {0949-8214}, doi = {10.15771/0949-8214_2004_1_1}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-3955}, pages = {5 -- 11}, year = {2004}, abstract = {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.}, language = {en} }