@misc{KornejewDimitrovHerzog2014, author = {Kornejew, Eckhart and Dimitrov, Kiril and Herzog, Michael}, title = {New aromatic polyesterpolyols derived from PET industrial wastes}, series = {Wissenschaftliche Beitr{\"a}ge 2014}, volume = {18}, journal = {Wissenschaftliche Beitr{\"a}ge 2014}, issn = {0949-8214}, doi = {10.15771/0949-8214_2014_1_9}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-3363}, pages = {71 -- 75}, year = {2014}, abstract = {China hat den globalen Recycling-Markt letztes Jahr mit der Ank{\"u}ndigung geschockt, nicht l{\"a}nger niederwertige Qualit{\"a}ten von rezyklierbaren Abf{\"a}llen von ausl{\"a}ndischen Exporteuren zu akzeptieren - die so genannte „Aktion Gr{\"u}ner Zaun" startete zu Beginn des Jahres 2013. Die Antwort im Westen sollte ein Innovations- und Investitionsschub in Recycling-Technologie zur Entwicklung eines erfolgreichen Recycling-Marktes sein. Dies sollte hochentwickelte Behandlungstechnologien und installierte Anlagentechnik umfassen. F{\"u}r PET-Getr{\"a}nkeflaschen aus den Pfandsystemen haben wir einen Prozess des rohstofflichen Recyclings entwickelt, mit dem Ausgangsstoffe f{\"u}r verschiedene technische Anwendungen gewonnen werden k{\"o}nnen. Die gewonnenen Aromatischen Polyesterpolyole (APP) dienen hierbei als Ausgangsstoffe zur Herstellung von Polyurethanen.}, language = {en} } @article{NjugunaMuchiriMwemaetal.2021, author = {Njuguna, James K. and Muchiri, Peter and Mwema, Fredrick M. and Karuri, Nancy W. and Herzog, Michael and Dimitrov, Kiril}, title = {Determination of thermo-mechanical properties of recycled polyurethane from glycolysis polyol}, series = {Scientific African}, volume = {12}, journal = {Scientific African}, issn = {2468-2276}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14911}, year = {2021}, abstract = {Polyurethane foam is one of the most versatile polymers widely used in the automotive industry. However, due to the rising amount of polyurethane foam waste in the environment, there is growing research attention focusing on circular economy solutions to closing the material loop. This study aimed to determine the possible changes in thermo-mechanical properties between rigid polyurethane prepared using polyols derived from depolymerization of commercial polyurethane foam with benchmark rigid polyurethane (Ben PU). Polyurethane foams containing dispersion polyol were reacted with dipropylene glycol (DPG) and diethylene glycol (DEG) with a ratio of DPG: DEG of 1:1 in the presence of a consumable catalyst (Di-n-butyl amine). The recovered polyol was used as a raw material replacing 100\% benchmark rigid polyurethane petroleum-based polyester polyol to produce the recycled polyurethane (Rec PU). Thermal analysis was conducted to measure the recycled polyurethane's glass transition temperatures (Tg) using differential scanning calorimetry (DSC). Tensile strength, elastic modulus, toughness, and hardness test of the recycled polyurethane were conducted under three different temperatures; 24°C, 40°C, and 60°C. From the DSC results, the glass transition temperatures for the recycled and the benchmark rigid polyurethane occurred at 43°C and 50.4°C, respectively. Both polymers showed the brittle-ductile transition from 24°C to 40°C. Tensile strength for recycled polyurethane was lower than that of benchmark rigid polyurethane by 29-43\% and a corresponding 24-50\% decrease in elastic modulus. Recycled polyurethane recorded lower toughness than petroleum-based pure polyurethane by 13-16\%. However, the recycled polymer recorded high shored D values than the benchmark rigid polyurethane by 9-29\%. This study reveals that recycled polyol could be used as feedstock for polyurethane production with applications tailored to its mechanical properties.}, language = {en} } @article{DimitrovHerzogNenkova2013, author = {Dimitrov, Kiril and Herzog, Michael and Nenkova, Sanchi}, title = {Fe3O4 Modification of Microcrystalline Cellulose for Composite Materials}, series = {American Journal of Chemistry}, volume = {3}, journal = {American Journal of Chemistry}, number = {5}, issn = {2165-8781}, doi = {10.5923/j.chemistry.20130305.04}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9651}, pages = {140 -- 147}, year = {2013}, abstract = {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.}, language = {en} }