Resistance of Scots pine Emphasis Type="Italic"

Authors: Shyamal C Ghosh Brenton C Peters Chris J Fitzgerald Holger Militz Carsten Mai

Publish Date: 2012/02/05

Volume: 46, Issue: 6, Pages: 1033-1041

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Abstract

Scots pine Pinus sylvestris L sapwood was treated with quatsilicone microemulsion 40 nm aminosilicone macroemulsion 110 nm alkylmodified silicone macroemulsion 740 nm and solutions of inorganic water glass Three treatment concentrations of 5 15 and 30 w/w were used for the impregnation of the test specimens Termite resistance was assessed following a 16week field trial conducted in northern Queensland Australia Two different field sites were chosen for exposure to feeding by Coptotermes acinaciformis Froggatt and Mastotermes darwiniensis Froggatt Following exposure the test and feeder specimens were inspected and assessed for termite damage using a visual rating system from 10 sound to 0 completely destroyed and individual mass losses The specimens treated with quat and aminosilicone emulsions resisted damage by both termite species even at less than 15 weight percent gains WPGs Alkylmodified silicone macroemulsion and water glass treatment induced somewhat less resistance to termite damage but imparted protection at higher WPGsTests for termite resistance of wood can be conducted under both laboratory and field conditions to compare the susceptibility of materials or to examine the performance of protective chemicals under test Howick and Creffield 1983 Laboratory test methods are usually adopted for the termiticide development research while the field tests can simulate the real inservice performance scenario of treated material Preston et al 1986 Several methods to protect wooden structures from termite damage include the use of naturally durable wood species preservative treatments and engineered wood products with enhanced insect and decay resistance Grace 2003 The reduced availability of naturally durable wood species however is increasing the dependence on the use of fastgrown nondurable wood for construction The protection of structures made of nondurable wood may require the application of broadspectrum insecticides The use of various organochlorine insecticides as chemical barriers to termites was a common practice until environmental concerns restricted their widespread applications French 1991 Present practices using insecticides as chemical preservatives are broadly categorized into three toxic levels such as repellent nonrepellent causing rapid mortality and nonrepellent with a delayed action Su et al 1982 Woodrow and Grace 2008 New safer treatment procedures in wood and soil are being constantly developed for effective termite control for example physical barriers using basaltic particles Tamashiro et al 1987 1991 and stainless steel mesh Lenz and Runko 1994 These have been developed as substitutes for soil treatment with chemicals Biological control measures have also been reported using natural parasites or predators to reduce termite population but show limited field efficacy Woodrow and Grace 2008A number of wood modification techniques have already been commercialized Hill 2006 substituting the use of toxic chemicals for wood protection Acetylation up to a WPG of 20–22 has been found to impart resistance to termite damage Imamura and Nishimoto 1986 Westin et al 2004 Furfurylated wood treated with medium 48 WPG and high concentration 92 WPG of furfuryl alcohol strongly resisted drywood and subterranean termite damage Hadi et al 2005 Furthermore wood modified with 13dimethylol45dihydroxy ethylene urea DMDHEU has recently been found to be resistant to Coptotermes acinaciformis at 13 and 21 mol l−1 but not to Mastotermes darwiniensis Militz et al 2008Treatment of solid wood with amino and ammoniumfunctionalised 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 alkylfunctionalised silicones imparted considerably lower resistance against fungi than the nitrogencontaining silicones These findings are promising with regard to the development of new wood protection processes but the effect of the sole treatment with silicone emulsions on the termite resistance has not yet been shownWater glasses are potassium or sodium silicates or solutions typically composed of 2–4 mol silicate and 1 mol alkali oxide They are soluble in water and form a colloidal clear heavily alkaline solution 12 pH at elevated temperatures and pressures Römpp 1995 Mai and Militz 2004 Wood treated with water glass has also been studied to improve the fungal decay Furuno et al 1991 1992 1993 Matthes et al 2002 and termite resistance Furuno and Imamura 1998 In this study wood treatment with commercial silicone emulsions with different functional groups and particle sizes as well as water glass was tested in order to assess the resistance against C acinaciformis Froggatt and M darwiniensis Froggatt in the field in northern Queensland Australia as previously described Peters and Fitzgerald 2004 Peters et al 2006 Militz et al 2008

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