Suchergebnisse

Aliphatic diisocyanates and their derivatives are key liquid components in the industrial processing of polyurethane materials. In particular, for the synthesis of crosslinked polyurethane materials, the higher functionality molecules obtained by reacting three -or more- diisocyanates are of interest. However, despite their widespread application, the relation between molecular structure and macroscopic physical properties, in particular viscosity, is poorly understood in these systems. In this work, we introduce a new force field parameter set, GAFF-IC, based on the widely-used and versatile GAFF force field, meant for accurate predictions of physical properties of isocyanate-based molecular liquids. The new parameters allow to predict the vaporization enthalpies and densities of several isocyanate-based molecules, which are found in excellent agreement with the available experimental data. The effectiveness and transferability of the improved parameters is verified by calculating the viscosities of several isocyanates, isocyanate dimers (uretdiones) and isocyanate trimers (isocyanurates), resulting in accurate viscosity predictions in excellent agreement with experimental values. ; This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sk lodowska-Curie Grant Agreement no. 642890 (http://thelink-project.eu/) and it was partially supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, and by the project "Search-ON2: Revitalization of HPC infrastructure of Uminho" (NORTE-07-0162-FEDER-0000869), under the National Strategic Reference Framework, through the European Regional Development ...

Aliphatic isocyanurates are nowadays used routinely in the development of advanced materials like polyurethane nanocomposites and 3D-printed components, due to their versatile reactivity and the good mechanical and optical properties they confer to the final material. In these applications, a control of the properties at the micro- and nanoscale is desired, therefore a deep understanding of intermolecular interactions is required. Using ab-initio calculations and molecular dynamics simulations, the intermolecular interactions of aliphatic isocyanurates are investigated in detail. The presence of an isocyanate-isocyanurate interaction is demonstrated, and the strong dispersion character of isocyanurate-based interactions is revealed. Calculations of the free energy of binding of the different interactions in gas and liquid phase are provided. The microscopic structure of aliphatic functional and non-functional isocyanurates is analysed and related to the different interaction types, and finally their possible relationship with macroscopic dynamic variables is discussed ; This project has received funding from the European Union's Horizon 2020 - Research and Innovation Framework Programme under the Marie Skłodowska-Curie Grant Agreement no. 642890 (http://thelink-project.eu/) and it was partially supported by the Portuguese Science and Technology Foundation (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, by the FCT grant SFRH/BD/128666/2017 and by the project " SearchON2: Revitalization of HPC infrastructure of Uminho" (NORTE07-0162-FEDER-0000869), under the National Strategic Reference Framework, through the European Regional Development Fund. The authors also acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing HPC resources that have contributed to the research results reported within this ...