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Anomalous bulk diffusion of methylene diphenyl diisocyanate in silicone elastomer

机译：硅氧烷弹性体中亚甲基二苯基二异氰酸酯的异常散装扩散

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摘要

In this study, we investigate the anomalous diffusion of methylene diphenylmethane-4,4'-diisocyanate (MDI) into fumed silica filled poly(dimethylsiloxane) (PDMS) elastomer, which occurs in the industrial application of polyurethane vacuum casting. The absorbed MDI polymerizes with moisture to polyurea within the silicone medium, forming a sequential semi interpenetrating polymer network. This results in the formation of polyurea clusters near the exposed surface. Here we focus on the spatially resolved chemical characterization on the micrometer scale utilizing time-of-flight secondary ion mass spectrom-etry (ToF-SIMS), transmission electron microscopy (TEM), helium ion microscopy (HIM), atomic force microscopy (AFM), thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) as well as nuclear magnetic resonance spectroscopy (NMR). The concentration profile was determined experimentally using a customized method based on TGA. It was shown that the polyurea reaction of the MDI causes a time-dependency of both the surface concentration and the diffusion coefficient. Six analytical solutions to the diffusion equation obeying different time-dependent boundary conditions with different physical implications are proposed and used to model the measured concentration profiles. The parameterized models showed good predictive power for the measured absorption data and thus substantiated the conjectured molecular phenomena.
机译：在该研究中，我们研究了亚甲基二苯基甲烷-4,4'-二异氰酸酯（MDI）的异常扩散到卷曲二氧化硅填充的聚（二甲基硅氧烷）（PDMS）弹性体中，这发生在聚氨酯真空铸造的工业应用中。吸收的MDI与硅氧烷介质内的水分聚合到多脲，形成连续半渗透聚合物网络。这导致在暴露表面附近形成聚脲簇。在这里，我们专注于利用飞行时间二次离子质谱 - etry（TOF-SIMS），透射电子显微镜（TEM），氦离子显微镜（HIM），原子力显微镜（AFM ），热重量分析（TGA），X射线光电子能谱（XPS）以及核磁共振光谱（NMR）。使用基于TGA的定制方法实验确定浓度分布。结果表明，MDI的聚脲反应导致表面浓度和扩散系数的时间依赖性。提出了六种分析方案，遵循不同的时间依赖性边界条件，并用于模拟测量的浓度分布。参数化模型向测量的吸收数据显示出良好的预测力，从而证实了昏暗的分子现象。

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  • 来源
    《International Journal of Heat and Mass Transfer》 |2021年第10期|121536.1-121536.13|共13页
  • 作者

    Martin Wortmann; Klaus Viertel; Alexander Welle; Waldemar Keil; Natalie Frese; Wiebke Hachmann; Philipp Krieger; Johannes Brikmann; Claudia Schmidt; Elmar Moritzer; Bruno Huesgen;

  • 作者单位

    Faculty of Engineering and Mathematics Bielefeld University of Applied Sciences Interaktion 1 33619 Bielefeld Germany;

    Faculty of Engineering and Mathematics Bielefeld University of Applied Sciences Interaktion 1 33619 Bielefeld Germany;

    Institute of Functional Interfaces Karlsruhe Nano Micro Facility Karlsruhe Institute of Technology Kaiserstr 12 76131 Karlsruhe Germany;

    Department of Chemistry Paderborn University Warburger Strasse 100 33098 Paderborn Germany;

    Faculty of Physics Bielefeld University Universitaetsstrasse 25 33615 Bielefeld Germany;

    Faculty of Physics Bielefeld University Universitaetsstrasse 25 33615 Bielefeld Germany;

    Faculty of Engineering and Mathematics Bielefeld University of Applied Sciences Interaktion 1 33619 Bielefeld Germany;

    Faculty of Engineering and Mathematics Bielefeld University of Applied Sciences Interaktion 1 33619 Bielefeld Germany;

    Department of Chemistry Paderborn University Warburger Strasse 100 33098 Paderborn Germany;

    Faculty of Mechanical Engineering Paderborn University Warburger Strasse 100 33098 Paderborn Germany;

    Faculty of Engineering and Mathematics Bielefeld University of Applied Sciences Interaktion 1 33619 Bielefeld Germany;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Anomalous diffusion; Time-dependent surface concentration; Time-dependent diffusion coefficient; Mathematical modelling; vacuum casting;

    机译：异常的扩散;时间依赖的表面浓度;时间依赖性扩散系数;数学建模;真空铸造;

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