The efficacy of commercial silicones against blue stain and mould fungi in wood

Abstract

Scots pine (Pinus sylvestris L.) samples were vacuum pressure impregnated with quaternary ammonium (quat)-silicone micro-emulsion (<40 nm particle size), amino-silicone macro-emulsion (110 nm) and silicone macro-emulsion with alkyl modified side groups (740 nm). Quat-silicone micro-emulsion caused highest cell wall bulking (4.8%) and anti-swelling efficiency (21.8%) in wood when treated with 30% concentration of silicone in the treatment solution. All three formulations made wood hydrophobic which was evident from a capillary (longitudinal, tangential and radial) water uptake test. Amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in strong resistance to blue stain attack with both pre-weathered and not pre-weathered wood samples. Signs of blue staining were more evident on the pre-weathered samples. Treatment with amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in a certain resistance to mould growth on wood surfaces, whereas wood treated with the same concentration of quat-silicone microemulsion and alkyl-modified silicone macro-emulsion exhibited comparatively lower resistance. Die Wirksamkeit kommerzieller Silicone gegenüber Bläue-und Schimmelbefall auf HolzZusammenfassung Kiefernholzproben (Pinus sylvestris L.) wurden unter Vakuum-Druck mit Emulsionen von drei Silicontypen imprägniert: der Mikro-Emulsion eines Sili-S. C. Ghosh · H. Militz · C. Mai (u) Wood Biology and Wood Products, Burckhardt Institute, Georg-August University, Büsgenweg 4, 37077 Göttingen, Germany e-mail: cmai@gwdg.de cons mit quaternären Ammoniumgruppen (Quat-Silicon, <40 nm Partikelgröße), der Makro-Emulsion eines AminoSilicons (110 nm) und der Makro-Emulsion eines Silicons mit alkyl-modifizierten Seitengruppen (740 nm). Die Mikro-Emulsion des Quat-Silicons verursachte die höchste Zellwandausdehnung (,,Bulking", 4,8%) und Quellvergü-tung (,,ASE", 21,8%) bei Holzproben, die mit 30%iger Siliconlösung behandelt wurden. Eine Untersuchung der kapillaren Wasseraufnahme (longitudinal, tangential und radial) machte deutlich, dass alle drei Formulierungen das Holz hydrophobieren.Die Makro-Emulsion des Amino-Silicons (10% SiliconKonzentration in der Behandlungslösung) bewirkte sowohl bei vorbewitterten als auch bei nicht vorbewitterten Proben eine hohe Resistenz gegenüber Bläuebefall. Hierbei war der Bläuebefall auf den vorbewitterten Proben deutlicher zu erkennen. Die Behandlung mit der Makro-Emulsion des Amino-Silicons (10% Silicon-Konzentration in der Behandlungslösung) ergab eine gewisse Resistenz gegenüber Schimmelbefall auf Holzoberflächen, während Hölzer, die mit der Mikro-Emulsion des Quat-Silicons und der MakroEmulsion des alkyl-modifizierten Silicons behandelt wurden, eine vergleichsweise geringe Resistenz aufwiesen.

Resistance of Scots pine (Pinus sylvestris L.) wood modified with functionalized commercial silicone emulsions against subterranean termites

“…The frequent use of quaternary ammonium compounds as wood preservatives has been reported by several authors (Preston et al 1987;Matejuk et al 2004;Pernak et al 1998Pernak et al , 2004Urbanik et al 1997). Ghosh et al (2008Ghosh et al ( , 2009 have reported that treatment with QuatSiMiE and AminoSiMaE increased the resistance of wood to staining, mould as well as white and brown rot decay fungi, while the AlkylSiMaE did not show such performance. Several reasons have been considered for the higher fungal resistance imparted by the treatment.…”

“…Treatment of solid wood with amino-and ammonium-functionalised silicones was shown to inhibit colonization by staining and mould fungi (Ghosh et al 2009) and fungal decay (Weigenand et al 2008;Ghosh et al 2008), and to impart moderate dimensional stability and water repellence (Weigenand et al 2007;Ghosh et al 2009). However, alkyl-functionalised silicones imparted considerably lower resistance against fungi than the nitrogen-containing silicones.…”

Effects of oleothermal treatment and polydimethylsiloxane (PDMS) coating on natural weathering of beech and fir woods

“…As mentioned in the introduction, wood treatment with silicon compounds can cause hydrophobic surface and improve the wetting properties of wood (Weigenand et al 2007, Ghosh et al 2009b. Figure 8 E and F for untreated samples and coated with PDMS as wellas Figure 8G and H for oleothermally treated samples and coated with PDMS show that unlike the colorimetric test and surface roughness, PDMS could significantly reduce the hydrophilicity of wood surface.…”

“…Accordingly, various nonpolar agents, such as oils, waxes, silanes or silicones have been used to achieve water resistant surfaces (Ghosh et al 2009b). In recent years, polydimethylsiloxane (PDMS) or silicones, as a hydrophobic agent, has gained special attention due to biocompatibility its optical and mechanical properties as well as its widespread industrial applications (Ghosh et al 2009b). By analogy with ketones, the name "silicone" was given in 1901 by Kipping to describe new compounds of the formula R 2 SiO (Figure 1).…”

“…The simultaneous presence of "organic" groups attached to an "inorganic" backbone gives silicones a combination of unique properties and allows their application in many fields like aerospace (low and high temperature performance), electronics (electrical insulation), health care (excellent biocompatibility) or in the building industries (weathering resistance) (Colas 2005). Silicones or PDMS have been reported to improve hydrophobicity and dimensional stability of wood (Weigenand et al 2007, Ghosh et al 2009b. Studies have also shown that the functional groups of silicones can reduce the growth of blue stain fungi and moulds on wood surfaces (Ghosh et al 2009a) and increase its resistance to fungal decay (Weigenand et al 2008, Ghosh et al 2009a).…”