The efficacy of commercial silicones against blue stain and mould fungi in wood
S C Ghosh, C Mai, H Militz
Scots pine (Pinus sylvestris L.) wood samples were vacuum pressure impregnated with quatsilicone micro emulsion (<40 nm particle size), aminosilicone macro emulsion (110 nm) and silicone macro emulsion with alkyl modified side groups (740 nm) and the resulting material properties were studied. Quatsilicone micro emulsion resulted in maximum bulking (4.8%) and anti-swelling efficiency (21.8%) in wood when treated with 30% concentration of silicone in treatment solution. All three chemicals made wood hydrophobic which was evident from capillary (longitudinal, tangential and radial) water uptake test adapted according to DIN 52617. Blue stain test EN 152 showed that aminosilicone macro emulsion (10% silicone in treatment solution) resulted in quite strong resistance to blue stain attack with both pre-weathered (1.2% staining of surface area) and not pre-weathered (0.2% staining of surface area) wood samples. Signs of blue staining were more evident on the pre-weathered samples which could be due to the break down of lignin, evident from the FTIR analysis. Blue stain development was evident by penetration of fungi through the ray cells visible in the cross sections of samples. Standard test for mould growth BS 3900 showed that wood treated with the aminosilicone macro emulsion (10% silicone in treatment solution) resulted in a delay and a certain degree of resistance to fungal growth on wood surfaces, whereas wood treated with the same concentration of quatsilicone micro emulsion and silicone macro emulsion with alkyl modified side group exhibited comparatively lower resistance.