Raw and analyzed data for manuscript "Preparation, surface characterization and water resistance of silicate and sol-silicate inorganic-organic hybrid dispersion coatings for wood"

Abstract

In this work, potassium silicate and potassium methylsiliconate aqueous solutions and their mixtures with a colloidal silica were used in the preparation of silicate and sol-silicate coatings. The white coating paints were brushed on beech wood substrates at a rate of 220 g·m⁻². The coatings exhibited good coverage ability. The pull-off adhesion strength values appeared to be related to pH following a polynomial law. The adhesion strength for the silicate coatings were adequate (above 3 MPa and up to 5 MPa) for wood, whereas the values for the sol-silicates were too low for practical applications. The adhesion values were in general higher for the samples cured in a climate room ((23±3) °C and (75±2) % relative humidity) than the samples cured in the ambient atmosphere of the laboratory ((23±3) °C and (25±5) % relative humidity). The presence of microdefects (cracks, holes) was revealed in the coating layers by optical and scanning electron microscopy. The surface roughness parameters assessed by confocal scanning laser microscopy were dependent on the magnification applied for their measurement. The arithmetic average roughness S_a was between 5 µm and 10 µm at magnification 5× and between 2.5 µm and 10 µm at magnification 20×. The maximum peak-to-valley height S_z confirmed the presence of open pores emerging through the coatings. The open porosities constitute free pathways for water ingress in the coatings, and could explain the high water absorption of the coatings including the methysiliconate-containing silicate coating and despite the relatively high water contact angle and low wettability exhibited by this sample. The post-application of a hydrophobizing solution containing hexadecyltrimethoxysilane and dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride considerably reduced the water permeability, while application of nanosilica-containing organic primers increased the adhesion for the coatings. Silicate coatings resistant against water damages can be generated on wood even without a primer, but an improvement of the paint formulations to control the formation of microcracks and open porosities could be useful to reduce the liquid water permeability and increase durability. Otherwise, the application of a hydrophobizing treatment can be used for this purpose.