Penetration of amino-silicone micro- and macro-emulsions into Scots pine sapwood and the effect on water-related properties

Abstract

Abstract An amino-silicone in the form of a micro- and a macro-emulsion (average particle size 40 and 120 nm, respectively) was tested in impregnation of solid wood. During vacuum-pressure impregnation, the uptake of 5% emulsions was only slightly reduced compared to water up-take. At 15% concentration, a significant reduction in emulsion uptake was observed, particularly in the radial and tangential directions of the wood. The penetration of silicone into the cell wall was dependent on the particle size of the emulsion. Applied as a macro-emulsion, a maximum of only 14% of the total silicone penetrated the cell wall, whereas 25–35% of the silicone was found in the cell wall when applied as a micro-emulsion. The degree of cell wall penetration of silicone for the micro-emulsion was confirmed by X-ray micro-analysis (SEM-EDX). The penetrated silicone caused bulking and dimensional stability. 1H NMR relaxometry T 2 distributions were determined for dried and moisture-conditioned wood samples. The silicone-treated specimens displayed spin-spin interactions of protons from water and silicones (or their emulsifiers). Conditioning of samples at 25°C and 65% relative humidity appeared to cause a decrease in the mobility of the non-water protons of the silicone and/or emulsifier. Freezing to -5°C caused separation of protons from bound water and from the silicone at low relaxation times. It is assumed that treatment with the micro-emulsion reduced water sorption due to micro-pore blocking in the cell wall. The formation of a sandwich complex is postulated, which comprises cell wall polymers, water molecules and a layer of silicone.