Comparative study of the properties of silicate coatings with different mineral pigments (titanium dioxide, iron (III) oxide, copper (II) oxide) on the surface of wood

IRG/WP 22-40936

A M Cheumani Yona, M Petrič

Silicate coatings are attractive alternatives to conventional organic-based coatings for wood protection. In this work, silicate coatings were prepared with a potassium silicate binder modified with a methyl siliconate solution, and three types of mineral pigments titanium dioxide, iron (III) oxide and copper (II) oxide. The coatings were applied on beech wood and cured under ambient conditions. The colour, surface roughness, adhesion strength, and resistance to cold liquids of the cured coatings were determined and reactions to fire of the coatings were compared using single flame source tests. The surface of wood was well masked by the coatings and the colour of the coatings was a function of the pigments. The coating layers were rough with arithmetic average roughness values Sa between 3 μm and 5 μm and maximum peak-to-valley height between 45 μm and 48 μm. The adhesion of the coatings was comparable, and sufficiently high (> 3 MPa) for application of the coatings to the surface of wood without a primer. The coatings were not considerably affected by the cold liquids. The single flame source tests showed that coatings containing titanium dioxide and copper (II) oxide reduced the charred area of the wood underneath, while coating with iron (III) oxide increased the charred area compared to the uncoated reference. A pigment such as iron (III) oxide which promotes the formation of char could produce an early layer of char at the surface of wood decreasing the spread of the fire within the wood. Further studies are planned to completely describe the fire behaviour of the coatings and extend the work to other pigments.

Keywords: silicate, coating, wood, adhesion, mineral pigment, fire retardancy

Conference: 22-05-29/06-02 Bled, Slovenia

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