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Identifier 000460261
Title Development of nanohybrid polyurethane coatings with self-healing properties
Alternative Title Ανάπτυξη νανοϋβριδικών πολυούρεθανικών επιστρωμάτων με ιδιότητες αυτοϊασης
Author Γιάνναρης, Κοσμάς
Thesis advisor Χρυσοπούλου, Κυριακή
Reviewer Αναστασιάδης, Σπύρος
Βαμβακάκη, Μαρία
Abstract In recent years, self-healing materials have been a subject of increased research interest due to their ability to self-repair damages either autonomically or by external stimuli, extending their lifetime or therefore assisting in the reduction of waste. Polyurethanes represent one of the most promising materials to use towards this direction. In particular, waterborne polyurethane dispersions (WPUDs) are widely used in coatings giving the additional advantage of the reduction of volatile organic compounds (VOCs) in the environment in comparison with the traditional coatings which are solvent-based. At the same time, inorganic and / or graphitic nano-additives are widely used to improve the mechanical, thermal, optical and electronic properties of a polymeric matrix resulting in polymer nanocomposites with an overall optimized behavior. In this work, nanohybrid polyurethane coatings were developed and their self-healing properties were evaluated. 2D materials like graphitic carbon nitride, g-C3N4, graphene oxide, GO, and Ti3C2Tx which belongs to the newly emerged class of Mxenes were dispersed in the polymeric matrix. The intrinsic self-healing mechanism of the WPUD can be improved by the presence of the inorganic compounds as they are anticipated to provide more hydrogen bonds due to the nitrogen and/or oxygen functional groups that exist on their surface or due to their ability to dissipate heat faster and thus increase the mobility of the polymer chains. Following the nano-additives synthesis, the materials were thoroughly characterized via X-ray Diffraction, XRD, Differential Scanning Calorimetry, DSC, as well as Raman and Infrared Spectroscopy, ATR-FTIR, measurements. WPUD nanocomposites were fabricated in different concentrations ranging between 0.05 - 1% wt. to investigate the effect of the additive content on the final properties. The PU/g-C3N4 nanocomposites were prepared via solid-liquid mixing while the PU/GO and PU/Ti3C2Tx via liquid-liquid mixing to avoid sedimentation problems. All nanocomposites were structurally and thermally characterized and no difference was observed in comparison to the properties of the pure PU due to the small amount of the nano-additives. Finally, coatings of all nanocomposites were fabricated by drop casting on silicon wafers. The coated surfaces were scratched creating deep and shallow cracks, using a razor blade and their self-healing efficiency was evaluated in two different temperatures (i.e., 75oC and 90oC). The healing procedure was monitored utilizing a Polarized Optical Microscope equipped with a Linkam heating stage. A quantification of the healing results was attempted by using mean grey value analysis. Similarities and differences were observed depending on the additive used; in certain cases, the self-healing ability of the pure polyurethane was found enhanced in the nanocomposites and the healing rate was found much higher, due to either better heat dissipation and / or the enhanced ability for hydrogen bond formation. Development of the polymer nanocomposite coatings with enhanced self-healing efficiency is anticipated to enhance their usage as varnishes in wooden floors as well as paints in the car industry.
Language English
Subject Αυτοϊαση
Νανουβριδικά επιστρώματα
Issue date 2023-11-29
Collection   School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Post-graduate theses
  Type of Work--Post-graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/6/d/6/metadata-dlib-1699357351-948091-26066.tkl Bookmark and Share
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