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Veröffentlichung The impact of water released from boehmite nanoparticles during curing in epoxy-based nanocomposites(2021) Waniek, Tassilo; Braun, Ulrike; Sielbernagl, DorotheeThe enhancing effect on mechanical properties of boehmite (y-AlOOH)nanoparticles (BNP) in epoxy-based nanocomposites on the macroscopic scaleencouraged recent research to investigate the micro- and nanoscopic proper-ties. Several studies presented different aspects relatable to an alteration of theepoxy polymer network formation by the BNP with need for further experi-ments to identify the mode of action. With FTIR-spectroscopic methods thisstudy identifies interactions of the BNP with the epoxy polymer matrix duringthe curing process as well as in the cured nanocomposite. The data reveals thatnot the BNP themselves, but the water released from them strongly influencesthe curing process by hydrolysis of the anhydride hardener or protonation ofthe amine accelerator. The changes of the curing processes are discussed indetail. The changes of the curing processes enable new explanation for thechanged material properties by BNP discussed in recent research like alowered glass transition temperature region (Tg) and an interphase formation. © AuthorsVeröffentlichung Molecular modelling of epoxy resin crosslinking experimentally validated by near-infrared spectroscopy(2019) Unger, Robin; Braun, Ulrike; Fankhänel, JohannesReliable simulation of polymers on an atomistic length scale requires a realistic representation of the cured material. A molecular modeling method for the curing of epoxy systems is presented, which is developed with respect to efficiency while maintaining a well equilibrated system. The main criterion for bond formation is the distance between reactive groups and no specific reaction probability is prescribed. The molecular modeling is studied for three different mixing ratios with respect to the curing evolution of reactive groups and the final curing stage. For the first time, the evolution of reactive groups during the curing process predicted by the molecular modeling is validated with near-infrared spectroscopy data, showing a good agreement between simulation results and experimental measurements. With the proposed method, deeper insights into the curing mechanism of epoxy systems can be gained and it allows us to provide reliable input data for molecular dynamics simulations of material properties. © 2019 Elsevier B.V.Veröffentlichung Molecular modelling of epoxy resin crosslinking experimentally validated by near-infrared spectroscopy(2021) Unger, Robin; Braun, Ulrike; Fankhänel, JohannesReliable simulation of polymers on an atomistic length scale requires a realistic representation of the cured material. A molecular modeling method for the curing of epoxy systems is presented, which is developed with respect to efficiency while maintaining a well equilibrated system. The main criterion for bond formation is the distance between reactive groups and no specific reaction probability is prescribed. The molecular modeling is studied for three different mixing ratios with respect to the curing evolution of reactive groups and the final curing stage. For the first time, the evolution of reactive groups during the curing process predicted by the molecular modeling is validated with near-infrared spectroscopy data, showing a good agreement between simulation results and experimental measurements. With the proposed method, deeper insights into the curing mechanism of epoxy systems can be gained and it allows us to provide reliable input data for molecular dynamics simulations of material properties. © The Author(s)Veröffentlichung Statuspapier Mikroplastikanalytik - Zusammenstellung wesentlicher Untersuchungsverfahren zur Probenahme, Aufbereitung und Detektion von Mikroplastik(2021) Braun, Ulrike; Stein, Ulf; Schritt, HannesUnter Mikroplastik sind Partikel, hauptsächlich bestehend aus synthetischen Polymeren, in der Dimension von 1-1000 (micro)m zu verstehen. Sie sind mittlerweile in der Umwelt allgegenwärtig, z.B. in Gewässern, Böden, Sedimenten und Luft, aber auch in Abwässern, Klärschlamm, Kompost und Lebensmitteln. In Umweltproben lassen sich in der Regel wenig große Partikel und sehr viele kleine Partikel von sehr unterschiedlicher Gestalt und chemischer Zusammensetzung identifizieren. Das macht ihre systematische Erfassung vergleichsweise aufwändig, sodass es eines guten Zusammenspiels verschiedener Verfahren bedarf. Obwohl die Charakterisierung von Plastik und von Partikeln seit Jahren etabliert ist, ist das Feld der Mikroplastikanalytik vergleichsweise jung. Daher müssen viele Verfahren erst noch hinsichtlich ihrer Eignung validiert werden. Es bestehen derzeit noch keine harmonisierten Protokolle. Das Statuspapier Mikroplastikanalytik fasst die Ergebnisse der Verbundprojekt-übergreifenden Diskussionen und Abstimmungen innerhalb des BMBF Forschungsschwerpunkts "Plastik in der Umwelt" zusammen. Es ist auf der Webseite des Forschungsschwerpunkts (https://www.bmbf-plastik.de/ index.php/de/publikationen) in deutscher und englischer Sprache zur Verfügung gestellt. © Authors