European Conference on Wood Modification 2007 105 Effects of Wood Treatment with Amino-silicone Emulsions on Different Material Properties Carsten Mai*, Oliver Weigenand, Shyamal Ghosh, Holger Militz Institute of Wood Biology and Wood Technology, Georg-August University, Büsgenweg 4, 37077, Göttingen, Germany [*E-mail: cmai@gwdg.de] Keywords: Amino-silicones, hydrophobation, penetration, SEM-EDX, basidiomycetes ABSTRACT Amino-silicone (AS) emulsions were tested for the impregnation of solid wood. The penetration of silicone into the cell wall was dependent on the particle size of the emulsions. Only a maximum of 14% of the total silicone penetrated the cell wall, when a macro-emulsion (120 nm average particle size) was used for the impregnation. In contrast, 25-35% of the silicone applied as a micro-emulsion (40 nm average particle size) was found in the cell wall and caused significant bulking and dimensional stability. The relatively high degree of cell wall penetration with regard to the micro-emulsion was confirmed through x-ray micro-analysis (SEM-EDX). Mini-blocks treated with high concentrations of AS micro-emulsion (15%) showed high decay resistance against Trametes versicolor and Coniophora puteana over a long term (12 weeks), while samples treated with low and moderate concentrations underwent considerable mass losses. INTRODUCTION Today the application of many conventional wood preservatives is under restriction due to their toxicity and growing customer awareness. In addition, most preservatives only exert a biocidal effect but do not change water related properties such as water uptake and moisture sorption or swelling and shrinkage. This provides a challenge to researchers to find environmentally acceptable solutions for efficient wood protection including dimensional stability and weathering resistance. Water repellents have been shown to reduce the deterioration of wood through weathering (Voulgaridis and Banks 1981). Moisture fluctuation in wood exposed to weather causes repeated swelling and shrinkage giving rise to the formation of checks and cracks and, in extreme cases, twisting, cupping and warping. Two of the main approaches of chemical treatment have been described which are implemented to reduce the moisture content as well as swelling and shrinkage of weathered wooden items. One approach is to bulk the cell wall by incorporating chemical spacers or to cross-link the cell wall polymers. The effect of the treatment is expressed as anti-swelling (shrinking)-efficiency (ASE). Most treatments that cause ASE are also able to reduce the equilibrium moisture content (EMC) of wood, i.e. the amount of bound water in the cell wall (Rowell 1983). Another approach is to impregnate wood with water repellents, such as oils, paraffins, silanes or silicones (Borgin and Corbett 1970, Mai and Militz 2004). These compounds cause macro-pore blocking by depositing a hydrophobic compounds in the lumens of vessels, of tracheids and of rays cells. Hydrophobic treatment does not generally diminish the EMC of wood since the number of hydroxyl groups and the pore structure of the cell wall are not altered by