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End date: 2020 × Start date: 2020 × Publisher: Amsterdam [u.a.] : Elsevier Science × WGL Institute: IPF ×

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Now showing 1 - 4 of 4
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    Thermal annealing to influence the vapor sensing behavior of co-continuous poly(lactic acid)/polystyrene/multiwalled carbon nanotube composites
    (Amsterdam [u.a.] : Elsevier Science, 2020) Li, Yilong; Pionteck, Jürgen; Pötschke, Petra; Voit, Brigitte
    With the main purpose of being used as vapor leakage detector, the volatile organic compound (VOC) vapor sensing properties of conductive polymer blend composites were studied. Poly(lactic acid)/polystyrene/multi-walled carbon nanotube (PLA/PS/MWCNT) based conductive polymer composites (CPCs) in which the polymer components exhibit different interactions with the vapors, were prepared by melt mixing. CPCs with a blend composition of 50/50 wt% resulted in the finest co-continuous structure and selective MWCNT localization in PLA. Therefore, these composites were selected for sensor tests. Thermal annealing was applied aiming to maintain the blend structure but improving the sensing reversibility of CPC sensors towards high vapor concentrations. Different sensing protocols were applied using acetone (good solvent for PS and PLA) and cyclohexane (good solvent for PS but poor solvent for PLA) vapors. Increasing acetone vapor concentration resulted in increased relative resistance change (Rrel) of CPCs. Saturated cyclohexane vapor resulted in lower response than nearly saturated acetone vapor. The thermal annealing at 150 °C did not change the blend morphology but increased the PLA crystallinity, making the CPC sensors more resistant to vapor stimulation, resulting in lower Rrel but better reversibility after vapor exposure.
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    Transparent model concrete with tunable rheology for investigating flow and particle-migration during transport in pipes
    (Amsterdam [u.a.] : Elsevier Science, 2020) Auernhammer, Günter K.; Fataei, Shirin; Haustein, Martin A.; Patel, Himanshu P.; Schwarze, Rüdiger; Secrieru, Egor; Mechtcherine, Viktor
    The article describes the adaption and properties of a model concrete for detailed flow studies. To adapt the yield stress and plastic viscosity of the model concrete to the corresponding rheological properties of real concrete, the model concrete is made of a mixture of glass beads and a non-Newtonian fluid. The refractive index of the non-Newtonian fluid is adjusted to the refractive index of the glass beads by the addition of a further constituent. The rheological properties of the model concrete are characterised by measurements in concrete rheometers. Finally, the first exemplary results from experiments with the model concrete are presented, which give incipient impressions of the complex internal dynamics in flowing concrete.
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    Examining the early stages of thermal oxidative degradation in epoxy-amine resins
    (Amsterdam [u.a.] : Elsevier Science, 2020) Morsch, Suzanne; Liu, Yanwen; Lyon, S.B.; Gibbon, S.R.; Gabriele, Benjamin; Malanin, Mikhail; Eichhorn, Klaus-Jochen
    Epoxy-amine resins continue to find widespread use as the binders in protective and decorative organic coatings, as the matrix in composite materials, and as adhesives. In service, exposure to the environment ultimately results in oxidative deterioration of these materials, limiting the performance lifetime. Defining this auto-oxidation process is therefore a key challenge in developing more durable high-performance materials. In this study, we investigate oxidative degradation of a model resin based on diglycidyl ether of bisphenol-A (DGEBA) and an aliphatic amine hardener, triethylenetetraamine (TETA). Using infrared spectroscopy, we find that prior to the expected detection of formate groups (corresponding to the well-known radical oxidation mechanism of DGEBA), a band at 1658 cm−1 forms, associated with amine cross-linker oxidation. Infrared microspectroscopy, in-situ heated ATR-infrared, Raman spectroscopy and AFM-IR techniques are thus employed to investigate the early stages of resin oxidation and demonstrate strong parallels between the initial stages of cured resin degradation and the auto-oxidation of TETA cross-linker molecules.
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    Discovery of hemocompatible bacterial biofilm-resistant copolymers
    (Amsterdam [u.a.] : Elsevier Science, 2020) Singh, Taranjit; Hook, Andrew L.; Luckett, Jeni; Maitz, Manfred F.; Sperling, Claudia; Werner, Carsten; Davies, Martyn C.; Irvine, Derek J.; Williams, Paul; Alexander, R.
    Blood-contacting medical devices play an important role within healthcare and are required to be biocompatible, hemocompatible and resistant to microbial colonization. Here we describe a high throughput screen for copolymers with these specific properties. A series of weakly amphiphilic monomers are combinatorially polymerized with acrylate glycol monomers of varying chain lengths to create a library of 645 multi-functional candidate materials containing multiple chemical moieties that impart anti-biofilm, hemo- and immuno-compatible properties. These materials are screened in over 15,000 individual biological assays, targeting two bacterial species, one Gram negative (Pseudomonas aeruginosa) and one Gram positive (Staphylococcus aureus) commonly associated with central venous catheter infections, using 5 different measures of hemocompatibility and 6 measures of immunocompatibililty. Selected copolymers reduce platelet activation, platelet loss and leukocyte activation compared with the standard comparator PTFE as well as reducing bacterial biofilm formation in vitro by more than 82% compared with silicone. Poly(isobornyl acrylate-co-triethylene glycol methacrylate) (75:25) is identified as the optimal material across all these measures reducing P. aeruginosa biofilm formation by up to 86% in vivo in a murine foreign body infection model compared with uncoated silicone. © 2020 The Authors