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Effect of Coatings on the Durability of Birch and Spruce Plywood. Part 2: Biological Durability
2010 - IRG/WP 10-40527
Several different coated birch and spruce plywood types were investigated in Finland using the combination of outdoor weathering and decay test EN 12038. The most important factor to affect on the biological performance of birch plywood, coated and uncoated, was edge sealing. For spruce plywood edge sealing had a smaller effect. However, in spite of positive effect against decay, edge sealing did not prevent wetting during the decay test. One year outdoor weathering did not have a significant effect on painted plywood when compared to samples stored in the laboratory.
A Nurmi, H Viitanen


An investigation of the effects of pre-steaming on the treatment of sawn spruce timber with Celcure A, a copper-chrome-arsenic preservative
1981 - IRG/WP 3150
Difficulties in the treatment of spruce using standard vacuum/pressure techniques with both water-borne and organic solvent preservatives are well known. We have evaluated the influence of steaming on treatability with a waterborne CCA preservative.
C R Coggins


Contribution to the testing of wood based board material
1982 - IRG/WP 2176
R G Lea


Fungal degradation of wood treated with metal-based preservatives. Part 2: Redox states of chromium
1996 - IRG/WP 96-10164
Concerns have arisen about the leaching of heavy metals from wood treated with metal-based preservatives, such as chromated copper arsenate (CCA). Of particular concern is the toxic redox state of chromium and arsenic in aging and decayed CCA-treated wood. Generally, hexavalent chromium is more toxic than trivalent chromium and trivalent arsenic is more toxic than pentavalent arsenic. The desired outcome from treating wood with CCA is total change of Cr(VI) to Cr(III) and As(III) to As(V). As part of an on-going study to determine the fate of copper, chromium and arsenic during aging and decay of CCA-treated wood, we detected Cr(III) and Cr(VI) in situ in CCA-treated southern yellow pine lumber. The redox states of Cr were determined using synchrotron X-ray fluorescence spectroscopy (SXRF). An SXRF microprobe was used to to detect Cr redox states by measuring X-ray absorption near-edge structure (XANES). The ratio of Cr(III) to Cr(VI) was determined (1) on the surface and interior of lumber two years after CCA treatment and (2) in lumber during decay by a CCA-tolerant fungus, Meruliporia incrassata TFFH-294. The XANES spectrum for Cr(VI) has a strong pre-edge feature that is not present in the spectrum for Cr(III). Only the Cr(III) XANES spectrum was detected on the surface and in the interior of the wood, indicating total reduction of Cr(VI). The XANES spectrum for Cr(III) was detected in wood after 12 week decay by Meruliporia incrassata TFFH-294, indicating that the fungus does not oxidize Cr(III) to Cr(VI) during the decay process. We are currently using XANES spectroscopy to detect and map in situ redox states of As in CCA-treated wood.
B Illman, S Bajt, T L Highley


A laboratory soil-block decay evaluation of plywoods edge-treated with preservatives
1982 - IRG/WP 2174
Preservative-treated plywood used under conditions or severe decay hazard frequently has its original, or cut edges, protected by the application of a field-cut preservative. This study uses a laboratory test method to compare the efficacy of four commercial preservative treatments against two commonly occurring brown-rot fungi. The results are not meant to indicate the service life of such treated plywood.
R S Smith, A Byrne


Testing method for the treatability of wood
1994 - IRG/WP 94-40031
In order to test and classify the treatability of wood species in pressure treatment processes with water-based solutions, a laboratory method was developed which allows the testing of small samples and limited sections of a stem, e.g. sapwood. The penetration of different liquids was determined separately concerning the three anatomical directions of wood. The common parameters for pressure impregnation were used on sap- and heartwood of eight indigenous and tropical wood species. An elastic epoxy resin proved feasible for coating the samples on five sides. From the data of the testing method a measure for the treatability was calculated, allowing to classify wood species into four treatability classes analogous to prEN 350-2 (1993).
A O Rapp, R-D Peek


Is there a need for re-sealing cut ends of envelope-treated softwood framing timber to protect against attack from Coptotermes spp. (Isoptera)?
2004 - IRG/WP 04-10524
The claim that Australian Coptotermes acinaciformis (Froggatt) do not appear to initiate attack on timber from the end grain, thereby negating the need for treating exposed cut ends of softwood framing material (35 x 90mm) which has a Tanalith™ T envelope, was investigated. Specimens of commercial Pinus radiata framing timber (untreated) and Pinus elliottii (untreated, envelope-treated) were partially enclosed in fine stainless steel mesh. Either cut ends (cuts at angles from 90° to 15º) or the sides of specimens were exposed to termites at three field sites in Australia: northern tropics (Darwin, NT), subtropical southeast coast (Brisbane, QLD) and temperate south-eastern inland (Griffith, NSW). C. acinaciformis is common at all sites. Results to date showed that this species of termite readily attacks timber from the end grain, including exposed cut ends of envelope-treated material. The patterns of attack observed for Coptotermes are similar to those of a number of other pest species of termites.
M Lenz, J W Creffield, S Runko


An investigation of the effects of pre-steaming on the treatment of sawn spruce timber with Celcure A, a copper/chrome/arsenic preservative
1981 - IRG/WP 3180
Difficulties in the treatment of spruce using standard vacuum/pressure techniques with both water-borne and organic solvent preservatives are well known. The growth characteristics of spruces (Picea spp) make them attractive candidates for forestry schemes. In 1975 the UK Forestry Commission had about 400 000 hectares, about 20% of total UK forest area, planted with Sitka spruce (Picea sitchensis). As an example of the situation in Scandinavia, the growing stock in Sweden consists of about 45% Norway spruce (Picea abies), 38% Scots pine (Pinus sylvestris) and the remainder hardwoods. The importance of spruce as a source of sawn timber in Europe is clear and we are investigating methods of improving the treatment of this timber. As part of the investigation we have evaluated the influence of steaming on treatability with a waterborne CCA preservative.
C R Coggins


Some aspects of testing water repellents
1998 - IRG/WP 98-40113
Several test methods are used to determine the efficiency of water repellent treatments on wood. The most common are: contact angle measurement, swelling rate of samples immersed under water and, the increase in mass of wood samples with time or after a fixed period of time either fully immersed under, or partially immersed in or floating on water. In this paper, some fundamental aspects of the latter, gravimetric method are discussed. Several wood species were tested in a water soak test and their mass increase was recorded after 24 hours. The influence of depth of immersion and factors such as axial sealing and water repellent treatment were included as variables. It was tested whether an increase in pressure occurred inside wood samples during complete immersion under water. Water uptake at different depths was found to be wood species depending. Increased pressure inside Pinus sylvestris samples completely immersed under water was observed. This could be attributed to compression of air resulting from the penetration of water during complete immersion.
D Lukowsky, M Farnow, T Rypstra


End grain sealing by polymer impregnation
1992 - IRG/WP 92-3708
The solution and dispersion characteristics of several hydrophobic derivatives of cellulose have been studied and the abilities of these polymers to afford effective end grain sealing of Corsican pine have been examined. Both solution and dispersion treatments with ethyl cellulose imparted good water repellency and end grain sealing to wood samples, however, the disperse systems possessed lower viscosities. Scanning Electron Microscopy (SEM) of treated samples and polymer radiolabelling/autoradiography studies indicated pit-membrane pore filtration of polymer particles close to the end grain. A range of esters (C2-C18 side chains) of Hydroxypropyl Cellulose have been prepared and characterised (FTIR, NMR). The acetyl, propyl and butyl esters formed coherent, flexible films. The C6, C9, C10 and C11 esters were essentially gums. However, the C18 (stearoyl) ester was found to form strong, wax like films, due to pronounced ester side-chain interactions. A number of the polymers were applied to Corsican pine test samples. Water repellent ability was found to strongly parallel the ability of the derivatives to form coherent polymer films. The C18 (stearoyl) ester exhibited impressive end grain sealing; outperforming all other systems tested at equivalent application levels. This work indicates that hydrophobic polymers that readily form strong films from solution or dispersion afford enhanced end grain sealing as compared to materials that simply produce a hydrophobic effect.
J M Lawther, W B Banks, D G Anderson, J A Cornfield


Re-sealing cut ends of envelope-treated softwood framing timber to protect against damage by the Australian subterranean termite Coptotermes acinaciformis: A revisitation
2006 - IRG/WP 06-20335
The claim that Australian Coptotermes acinaciformis (Froggatt) do not appear to initiate damage on timber from the end grain, thereby negating the need for treating exposed cut ends of softwood framing material (35 ? 90 mm) which has a repellent Tanalith? T envelope, was further investigated. Specimens of commercial Pinus radiata D.Don framing timber (untreated) and Pinus elliottii Englem. (untreated and envelope-treated) were partially clad in fine stainless steel mesh. Clad and unclad specimens were exposed to C. acinaciformis near Townsville, Australia, for four months. Results showed that this species of termite can damage timber from the end grain, including exposed cut ends of envelope-treated material. Differences between these and other test conditions (where C. acinaciformis did not damage timber from the end grain) are discussed. Clearly, outcomes from laboratory and field studies with preservative-treated materials are dependent upon experimental conditions. The amount of feeder material offered in a given method can strongly influence the termite response. Further investigation is required to standardise this aspect of conditions in protocols for assessment of wood preservatives.
B C Peters, M Lenz, J W Creffield


Comparison of moisture loss and its increment during the rehearsal process based on natural drying and water soaking application with or without sealing the trial discs of Common black poplar (Populus nigra L.)
2013 - IRG/WP 13-40639
This study was subjected to be set up to prove the pattern of moisture loss and moisture increment within the same wood samples prepared as the discs (30x23±3 cm diameter) with or without the bark intact during drying and in the duration of the water soaking application. In this concept, wood was exemplified by Common black poplar (Populus nigra L.) of the five 12 year old trees that are grown indigenously in the same wooded area. The moisture loss was checked by the natural drying process of 25 days, and the moisture increment was tested by the water soaking application of 25 days. Both natural drying process and water soaking application were carried out in the manner that one after the other based on the interdependent relationship between experimental condition and wood moisture content. The two tests were designed: test 1 was took place at the standard room temperature and relative humidity, and arranged with the experimental wood samples of the control (debarked), the unsealed (debarked before water soaking), the sealed (around the disc was coated with waterproof material before drying), test 1 was conducted at the warmer and cooler places indoor at the air temperature of 23 °C and 18 °C respectively, and the water temperature of water was at 20 degrees Celsius for soaking application. The experimental observations showed that the condition of the experimental area and the situation of the wood samples were more effective for either loosing or gaining moisture. The bark illustrated the ability to regulate evaporation of free water in the wood during natural drying and the stable condition of the experimental places that decreased the sapwater loss per unit of processive time after 15 days. According to the experimental findings, the dried-wood has limited potential for receiving the similar moisture content at once it was dried to below the fibre saturation point. In this case, the ability to recover of naturally dried-wood in the frame of moisture increment at the end of the water soaking application was found to be just over half of the initial moisture level before the natural drying process was started.
I Usta