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A novel technique for comparative toxicity studies of potential insecticidal wood preservatives
1983 - IRG/WP 2198
For some years now a device has been under development at the New Zealand Forest Research Institute, the purpose of which is to study the effects of sub-lethal amounts of stomach poisons (but also of fumigants and contact active materials) on the co-ordinative abilities of a cerambycid larva. This insect is Prionoplus reticularis - indigenous to New Zealand its larvae feed in decaying logs and are very common in Pinus radiata plantations. The intention of the programme has been to speed-up the screening of potential wood preservatives, deriving reproducible toxicity data in the fastest possible time. The machine itself, now termed a „repentiometer“ for lack of a better name, has been fully described elsewhere (Cross - in press), but a brief resume will be given here. Essentially it consists of two contra-rotating belts, placed one above the other, between which a larva of 0.8 to 1.2 g weight attempts to crawl (Prionoplus larva have greatly reduced legs that serve no purpose in moving along; crawling in tunnels is achieved by rhythmic turgor changes along the body). Since at this stage in its life the insect is intensely thigmotactic, i.e. will squeeze into any confined space offered rather than roll around free, there is no difficulty in getting them into the correct position. However, considerable electronic sophistication is needed to keep them there once the belts are moving, the speed of rotation being adjusted through two means, i) if the larva overtakes the belts the voltage to the driving motor is stepped up by a factor of 10, so forcing the larva back, ii) if the larva slows relative to the belts and is pushed out backwards then it makes contact between two electrodes, this reduces voltage by a small amount while at the same time supplying a mild electrical stimulus to the insect. Having now arrived at the correct speed range, and with these feedback controls working reliably, the repentiometer functions very well. It provides a very sensitive method of examining the effects of toxicity on an intact insect system, whether the chemicals under test are force fed or injected directly into the haemocoel (Cross 1979).
D J Cross


Laboratory decay test of Burmese in and kanyin treated with three wood preservatives
1982 - IRG/WP 3210
Laboratory decay tests were performed on samples of In (Dipterocarpus tuberculatus Roxb.) and Kanyin (Dipterocarpus alatus Roxb. and Dipterocarpus turbinatus Gaertn f.) pressure treated with three wood preservatives - copper arsenic additive (CAA - a variation of ammoniacal copper arsenate), Arquad C-33 (a waterborne quaternary ammonium formulation), and tributyltin acetate (TBTA) dissolved in ethanol. Pressure treatments with each preservative involved a 0.5 - 1 hour vacuum followed by a 4 hour period of pressure. This resulted in a very variable treatment because of the inherent difficulty in treating these woods. The decay tests entailed a slightly modified form of the AWPA M10-77 standard soil-block test using three brown-rot and three white-rot fungi. The untreated In and Kanyin samples were moderately susceptible to decay though weight losses were very variable and some samples of Kanyin (usually the densest and least permeable) were naturally resistant. At the concentrations tested CAA was the most effective in reducing weight losses incurred in the soil-block tests. TBTA was successful in controlling decay caused by all but two of the test fungi. It is suggested that preservative retentions for TBTA conforming to those included in the Candadian standard for bis (tributyltin) oxide would exceed the toxic limit for all the fungi tested
J N R Ruddick, R S Smith, A Byrne


A new wood preservative based on polymerized complexes of aminotriazole with copper acetate
1998 - IRG/WP 98-30169
This paper presents the results of preliminary fungitoxicity tests as carried out on new polymerized complexes of aminotriazole with copper acetate (PCC) against Coniophora puteana and Trichoderma viride. Laboratory tests on wood confirmed the findings arrived at in the screening test on agar medium. Deep penetration into pine wood of compounds studied was observed and particularly so at humidity above the point of fiber saturation (up to 10 mm in manual treatment), as well as good fixation in wood. Together with quaternary ammonium compounds (QAC) a strong synergistic effect towards the microorganisms tested was evident. The formulations investigated in the present study seem promising for future use in the wood preservation. Their practical implementation may enable effective control of wood destroying agents.
K J Krajewski, A Lukasiewicz, J Wazny


An investigation into the stability of TBTO in LOSP-treated radiata pine
1987 - IRG/WP 3459
Nuclear magnetic resonance (NMR) spectroscopy and reverse phase paper chromatography were used to characterise the organotin compounds found in radiata pine treated with bis (tri-n-butyl) tin oxide (TBTO). Preliminary results indicate that the preservative is remarkably unstable in wood after light organic solvent preservative (LOSP) treatment. Significant decomposition of TBTO occurs in a matter of hours. White crystalline material observed on the surface of treated wood was identified as tributyltin acetate (TBTA). Other tributyltin esters, dibutyltin ethers, and butyltin chlorides were also identified.
K J Archer, R Meder


Effect of fatty acid removal on treatability of Douglas-fir
1993 - IRG/WP 93-40008
Treatment of Douglas-fir with chromated-copper-arsenate (CCA) poses a major challenge. Several hypotheses based on the anatomical aspects as well as chemical reactivity of the preservative formulations with cell wall constituents and deposits have been proposed. Techniques to prevent pit aspiration or slow fixation reactions have, however, not significantly improved treatment. The presence of high molecular weight fatty acids have been reported to be responsible for higher hydrophobicity in some wood species. These acids can react with Cu+2/Cr+3 ions to form insoluble metallic soaps, thereby immobilizing Cu/Cr and increasing wood hydrophobicity by a mechanism similar to that employed in paper sizing. The effect of fatty acids on treatability was explored by removing these components via several extraction methods. In general, extracted wood had higher gross solution absorptions and chemical retentions, but preservative penetration was largely unaffected. The results suggest that removal or disruption of fatty acids can improve treatability of Douglas-fir heartwood.
S Kumar, J J Morrell


Mechanical resistance of Pinus radiata CCA treated and face jointed with PVA adhesive
1999 - IRG/WP 99-40140
Due to the increased use of Pinus radiata timber composites (laminated structural members, panels, etc), its low natural durability and the toxicity of phenol-formaldehyde type adhesives, a PVA (polyvinyl acetate) adhesive was evaluated in machined and rough CCA treated and untreated face joint samples under DIN 68602 (EN 204-205) standard for groups of requirement 3 and 4. The results showed that the adhesive resisted the face joint in machined samples without CCA treatment. Rough wood samples did not meet the standard. The effect of the CCA treatment up to 4 kg oxide/m3 prior to the bonding produced a decrease in the mechanical strength of the joint in both types of roughness. Treated and machined samples had similar behaviour as rough untreated samples. The selected adhesive is not good in applications on weather exposed service of composites, since in group 3 requirement all samples failed the bending test at the adhesive joint and not at the clean wood portion.
M C Rose, L Reyes, P León


Wood surface pretreatments with metal tannates
1989 - IRG/WP 3552
The sequential application of aqueous solutions of tannins derived from radiata pine bark and water-soluble metal salts was examined as a means of improving the water repellency of wood surfaces. Nine metal salts were screened in combination with tannin solutions and, based on water repellency of pretreated filter paper, four were selected for further study. The two-step application of tannin solution and copper acetate solution resulted in water repellency on paper or wood surfaces that compared favourably with that introduced by a chromic acid control treatment. Leaching studies showed that significant quantities of the metal complexes precipitated on the wood surface could be removed by water leaching. Further work is now in progress to evaluate the exterior performance and photostability of the surface pretreatments.
D V Plackett, D R Cronshaw


A comparison of the leaching resistance of copper 2-ethanolamine and copper ethylenediamine treated Scots pine
2000 - IRG/WP 00-30233
The depletion of copper from copper 2-ethanolamine and copper ethylenediamine treated Scots pine blocks was investigated. A greater leaching resistance was found for copper 2-ethanolamine, which retained ca. 86% and ca. 50% copper after water and buffer leaching, respectively. Leached amine treated blocks also contained significant residual amine. This was consistent with other observations linked to the formation of amine acid salts in amine treated wood. The results also suggested that significant loss of copper, due to formation of copper acetate can occur.
Xiao Jiang, J N R Ruddick


Influence of Polyvinyl acetate emulsion (PVA) on boron leaching and fungicidal properties
2008 - IRG/WP 08-30451
Boron compounds are very effective fungicides, but unfortunately they leach from wood. In order to improve boron fixation, boric acid, borax were combined with polyvinyl acetate emulsion (PVA). For comparison copper salts were included into this research as well. Selected preservative solutions were chosen for impregnation of Norway spruce wood specimens (Picea abies). Wood blocks were exposed to three wood decay fungi Antrodia vaillantii, Gloeophyllum trabeum and Trametes versicolor according to the mini block procedure. Part of impregnated specimens was leached according to the EN 1250-2 procedure. The results showed that addition of PVA emulsion slightly improves copper and boron fixation. Spruce wood impregnated with the lowest concentration of boron based solutions (cB = 0.1 %) was found resistant against tested fungi. In contrast, wood blocks impregnated with copper were sufficiently protected against G. trabeum and T. versicolor but not against A. vaillantii. Furthermore, PVA itself has a negative impact on fungal growth, and it improves performance of boron and copper based aqueous solutions.
M Humar, B Lesar, P Kralj


Effects of intumescent formulation of vinyl acetate-based coating on flame-retardancy of thin painted red lauan (Parashorea spp.) plywood
2011 - IRG/WP 10-40537
Using intumescent coatings on wood-based materials is an effective method for fire safety. The intumescent coatings consist of four major components: (1) binder resin (BR), (2) carbonizing substance (CS), (3) foam producing substance (FPS) and (4) dehydrating agent (DA). Previous studies have demonstrated that the formulation of the four components strongly influences the performance of coatings. This study investigated the effect of intumescent formulation of vinyl acetate-based coating on flame-retardancy of plywood. Two sorts of widely used binder resin (BR) for vinyl acetate-based coating, ethylene vinyl acetate copolymer (EVAc) and vinyl acetate acrylic copolymer (VAC), were used. The fire retardancy of coatings on plywood was assessed by a cone calorimeter. Total heat release and time to peak heat release rate are the two primary parameters. The data showed that lower BR and FPS content decreased total heat release and lengthen time to peak heat release rate. This mechanism to achieve better fire performance was verified by using oxygen bomb calorimeter and thermogravimetrical analysis, exhibiting lower heat of combustion and weight loss. The lower BR and FPS content can extend the survival duration of phosphor-carbonaceous chars. The results provide information for designing vinyl acetate-based coating.
Chih-Shen Chuang, Kuang-Chung Tsai, Te-Hsin Yang, Ming-Kuang Wang, Chun-Han Ko


Accelerated weathering and fungal resistance of wood modified with isopropenyl acetate
2016 - IRG/WP 16-40764
Chemical modification of Rubberwood (Heveabrasiliensis Müll.Arg) with isopropenyl acetate (IPA) in presence of anhydrous aluminum chloride and iodine as catalysts was carried out. Modified wood surfaces were exposed to UV light source in an accelerated weathering tester to evaluate UV resistance. Anti-swelling efficiency (ASE) and fungal resistance of modified wood were also evaluated. Modified wood showed good ASE. Decay resistance of modified wood was evaluated by exposing unmodified and modified wood to a brown rot (P. meliae) and white rot (T. hirsuta) fungi. Results indicate that chemical modification of wood with IPA is effective in restricting photo-yellowing at wood surfaces. Modified wood inhibited decay due to brown rot and white rot fungi. Good ASE, increased fungal resistance and UV resistance of modified wood indicates IPA as a promising reagent for modification of wood.
G B Nagarajappa, K K Pandey