Protective Particle Coatings applied by Cold Plasma Spraying
von Lena Wallenhorst
Datum der mündl. Prüfung:2017-12-18
Erschienen:2018-03-07
Betreuer:Prof. Dr. Gisela Ohms
Gutachter:Prof. Dr. Gisela Ohms
Gutachter:Prof. Dr. Wolfgang Viöl
Gutachter:Prof. Dr. Holger Militz
Dateien
Name:DissertationRevised_LenaWallenhorst.pdf
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Zusammenfassung
Englisch
In this thesis, two different types of particle coatings deposited by cold plasma spraying on wood and glass substrates were investigated in an attempt to achieve protection of wood or other surfaces, particularly in outdoor applications. The first type involved coatings comprised of zinc and zinc oxide that were deposited from elemental zinc. Zinc oxide features several properties favourable to wood protection, such as absorption of ultraviolet light. Indeed, UV-blocking properties of semi-transparent coatings on acrylic glass were confirmed and UV-induced discolouration of wood could be distinctly reduced by coatings with increased particle concentration. Coating systems comprising a Zn/ZnO particle coating and a polyurethane (PUR) top coat were found to decrease photodiscolouration without damage to the PUR matrix by photocatalytic decomposition. The second type of coating involved the deposition of a powder made of poly(methyl methacrylate) (PMMA), reinforced with aluminium trihydrate (ATH or Al(OH)3) filler particles. This powder constitutes an industrial waste of a bulk material that has properties usable in wood protection; hence, its deposition was studied in order to explore a method of recycling the powder to make use of the material’s protective potential. The deposition of pure PMMA/ATH powder yielded coatings with insufficient abrasion resistance, but their characterisation confirmed a certain potential to bond well, particularly to polar matrix materials. Particle fixation was achieved by the addition of a phenol-formaldehyde (PF) powder to the PMMA/ATH raw material. Studies on the coating’s morphology and chemical composition suggest a film formation of the reacted PF which encased the PMMA/ATH particles and the generation of covalent bonds between the layer and the substrates as adhesion mechanisms.
Keywords: Plasma Coatings; Wood Protection; Zinc Oxide; PMMA/ATH; Recycling; Adhesion; Surface Characterisation