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- ItemInsulin adsorption to catheter materials used for intensive insulin therapy in critically ill patients: Polyethylene versus polyurethane - possible cause of variation in glucose control?(Sharjah : Bentham Science Publishers B.V., 2014) Ley, S.C.; Ammann, J.; Herder, C.; Dickhaus, T.; Hartmann, M.; Kindgen-Milles, D.Introduction: Restoring and maintaining normoglycemia by intensified insulin therapy in critically ill patients is a matter of ongoing debate since the risk of hypoglycemia may outweigh positive effects on morbidity and mortality. In this context, adsorption of insulin to different catheter materials may contribute to instability of glucose control. We studied the adsorption of insulin to different tubing materials in vitro and the effects on glycemic control in vivo. Materials and Methods: In vitro experiments: A syringe pump was filled with 50 IU insulin diluted to 50 ml saline. A flow of 2 ml/h was perfused through polyethylene (PET) or polyurethane (PUR) tubing. Insulin concentrations were measured at the end of the tube for 24 hours using Bradford's protein assay. In vivo study: In a randomized double-blinded cross-over design, 10 intensive care patients received insulin via PET and PUR tubes for 24 hours each, targeting blood glucose levels of 80-150 mg/dl. We measured blood glucose levels, the insulin dose required to maintain target levels, and serum insulin and C-peptide levels. Results: In vitro experiments: After the start of the insulin infusion, only 20% (median, IQR 20-27) (PET) and 22% (IQR 16-27) (PUR) of the prepared insulin concentration were measured at the end of the 2 meter tubing. Using PET, after one hour infusion the concentration increased to 34% (IQR 29-36) and did not increase significantly during the next 24 hours (39% (IQR 39-40)). Using PUR, higher concentrations were detected than for PET at every measurement from 1 hour (82% (IQR 70-86)) to 24 hours (79% (IQR 64-87)). In vivo study: Glycemic control was effective and not different between groups. Significantly higher volumes of insulin solution had to be infused with PET compared to PUR (median PET 70.0 (IQR 56-82) ml vs. PUR 42 (IQR 31-63) ml; p=0.0015). Serum insulin concentrations did not decrease significantly one hour after changing to PET or PUR tubing. Conclusion: Polyurethane tubing systems allow application of insulin with significantly lower adsorption rates than polyethylene tubing systems. As a consequence, less insulin solution has to be infused to patients for effective blood glucose control. Tubing material of the insulin infusion may be crucial for safe and effective glycemic control in critically ill patients.
- ItemDetermination of Strain Limits for Dimensioning Polyurethane Components(Basel : MDPI, 2021) Stanko, Michael; Lehmenkühler, Peter; Stommel, MarkusWithin the scope of this contribution, a method for the determination of a strain limit for designing components made of elastomeric polyurethane systems is presented. The knowledge of a material-specific strain limit is essential for the structural-mechanical calculation of plastic components in the context of component design. Compared to a commonly used component design, based on a simplified dimensioning approach taking only linear viscoelastic deformations into account, the strain limit determined in this study allows an improved utilisation of lightweight construction potential in the dimensioning of technical components made of polyurethanes through the consideration of permissible nonlinear viscoelastic deformations. The test method comprises a sequence of quasi-static loading and unloading cycles, with a subsequent load-free recovery phase, allowing the relaxation of the viscoelastic forces. Standardised tensile and simple shear test specimens and a dynamic mechanical thermal analyser (DMTA) are used within the tests. The strain limit is determined by means of the so-called residual energy ratio, which is a characteristic quantity for the evaluation of hystereses of load–unload cycles. These hystereses are increasingly formed by deformations outside the range of linear viscoelastic deformations. The residual energy ratio relates the proportion of deformation energy recovered during unloading to the deformation work that is applied. In this contribution, the residual energy ratio is successfully used to detect a significant evolution of loss energy under increasing load and to correlate this transition to a characteristic strain. The latter is used as a dimensioning parameter for the design of components made of elastomeric polyurethane materials for quasi-static load cases. The determination of this strain limit is performed under consideration of the criterion of reversibility of deformation.
- ItemAbschlussbericht zum Verbundvorhaben "Neuartige Polymere auf Basis von Triglyceriden" : Darstellung der erzielten Ergebnisse für die Teilvorhaben mit den Partnern ; Teilvorhaben 1: Entwicklung von Katalysatoren und Herstellung neuer Monomere, Leibniz-Institut für Katalyse e.V. an der Universität Rostock (LITKAT) ; Teilvorhaben 2: Herstellung der Polyamide und Polyurethane, Fraunhofer-Institut für Chemische Technologie (ICT) ; Teilvorhaben 3: Entwicklung von Verfahren zur Herstellung von Monomeren für Kunststoffe aus plfanzlichen Ölsäuren, Evonik Oxeno GmbH (Oxeno) ; Teilvorhaben 4: Herstellung der Polyamide sowie Bewertung, Evonik Degussa GmbH (High Performance Polymers [HPP]) ; Teilvorhaben 5: Herstellung der Polyurethane sowie Bewertung und Dokumentation, Rampf Ecosystems GmbH & Co KG ; Laufzeit des Vorhabens/Berichtszeitraum: 01.10.2008 bis 31.12.2011(Hannover : Technische Informationsbibliothek (TIB), 2012) Kugler, Michael; Baumann, Franz-Erich; Fehrenbacher, Ulrich; Fridag, Dirk; Köckritz, Angela; Petrat, Frank-Martin; Tübke, Beatrice; Walter, Guido[no abstract available]
- ItemEntwicklung eines kratzfesten, transparenten Pulverlackes(Saarbrücken : Universität des Saarlandes, 2014) Jochum, MarlonIm Rahmen der Arbeit wurde versucht einen transparenten, kratzfesten Pulverlack herzustellen. Es wurden kommerziell erhältliche Böhmitnanopartikel auf ihre Eignung als Kompositbestandteil untersucht und mit einem zweikomponentigen Poly\-ur\-ethan\-ma\-trix\-sy\-stem als Pulverlackbinder kombiniert. Zur Herstellung eines Komposites wurden die Bestandteile in einem Heissextrusionsverfahren ineinander dispergiert. Es wurden sowohl modifizierte als auch unmodifizierte Böhmitpartikel zur Kompositherstellung verwendet. Eine Art Böhmitpartikel wurde mit einem Isocyanatosilan modifiziert und ebenfalls Komposite hergestellt. Die Böhmitpartikel wirkten sich positiv auf die Stabilität der Bindermatrix aus, allerdings ohne die Kratzfestigkeit merklich zu erhöhen. Aus den mit Isocyanatosilan modifizierten Böhmitpartikeln wurden Komposite mit wechselndem Komponentenverhältnis hergestellt. Dabei wurde festgestellt, daß die modifizierten Partikel mit der Matrix eine leichte Bindung eingehen und diese verfestigen.