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Stabilisation of nano - SiO2 particles in 2 K Polyurethane containing clearcoats by use of carboxylic acids

Stabilisierung von SiO2-Nanopartikeln in 2 K-Polyurethane enthaltenden Decklacken unter Verwendung von Carbonsäuren
: Stenzel, V.; Wilke, Y.; Brinkmann, A.

Rhodia SA, Boulogne-Billancourt:
Polyurethanes for high performance coatings V : EC, European Coatings Conference. Berlin/Germany, 14 - 15 February 2008
Hannover: Vincentz, 2008
European Coatings Conference "Polyurethanes for High Performance Coatings" <5, 2008, Berlin>
Fraunhofer IFAM ()
Polyurethanbeschichtung; Zweikomponentenwerkstoff; Beschichtungsmittel; Deckschicht; Füllstoff; Siliciumdioxid; Nanopartikel; Ausflocken; Verhütung; Stabilisierung; Carbonsäure; Lackadditiv; Kratzfestigkeit; Scheuerfestigkeit; optische Transparenz

A new method for the stabilisation of SiO2-nanoparticles, which are produced in an UV-curable resin by a Sol-Gel-process, was developed. These particles have, due to the production process, hydroxyl-groups on their surface. These groups can lead to a flocculation of the particles during addition of free isocyanates to the dual-cure-clearcoat. A method for the stabilisation of nano-particles in the matrix was applied, which permits concentrations up to 40% SiO2 without flocculation. As stabilising-agent organic acids have been used, whose intermolecular hydrogen bonding is responsible for the prevention of flocculation. The stabilising-agent carries also a double bond, which participates in the UV-initiated radical-polymerisation, so that a network between the anorganic nanoparticles and the organic matrix generates. The resulted clearcoat shows good properties in abrasion- and scratch resistance. Transparency, gloss and levelling of the nanoparticie containing coatings were very good. The optimal size and concentration of nanoparticles for different applications have been investigated.
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