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Studies on accelerated ageing procedures with TBTO-treated wood
1985 - IRG/WP 2244
The efficacy of various procedures for accelerated ageing of organotin based wood preservatives in treated wood has been investigated. It was found that leaching of the treated wood samples in water according to the European Standard EN 84 was not satisfactory for organotin based preservatives and is probably also unsuitable even for other types of organic solvent preservatives. Keeping tributyltin oxide (TBTO) treated samples in a heating cabinet at 70°C for five weeks, however, had a considerable effect on the breakdown of TBTO and the subsequent decay test. Therefore, an ageing procedure involving a heating period should be considered for all organic solvent wood preservatives. The investigation also confirmed that elevated temperatures accelerate the degradation of TBTO and that there is a strong correlation between the percentage of TBTO in the wood and its resistance against decay.
J Jermer, M-L Edlund, B Henningsson, W Hintze


Studies of the distribution and degradation of tributyltin naphthenate in double-vacuum treated wood
1983 - IRG/WP 3230
The effects of forced solvent evaporation by kilning redwood (Pinus sylvestris) that has been double-vacuum treated with tributyltin naphthenate (TBTN) have been investigated. Contrary to previous studies reported, it has been shown that forced evaporation can have a considerable influence on the losses of the fungicide. It has been found that, whether the solvent is allowed to evaporate slowly or the evaporation is forced by kilning, the TBTN breaks down considerably in freshly treated wood. In view of the implications of this work for the long-term effectiveness of TBTN further studies are called for.
J Jermer, M-L Edlund, W Hintze, S V Ohlsson


How to determine what is a realistic emission from treated wood - basic reflections
1998 - IRG/WP 98-50105
Emissions from treated wood occur by evaporation and by leaching. Up to date by far more experience exists on leaching tests than on evaporation test. The methods applied will be of interest to give answers to the questions about the quantity of possible emissions. Standardisation on leaching started very early. One of the first attempts to quantify the effect of leaching on the remaining efficacy was the German DIN 52176-2 (1941) which was the basis for EN 84 first published by CEN in 1978. A specific German standard for the determination of leachates was published in 1972 (DIN 52172-2), however, the viewpoint was still the efficacy of wood preservatives. With respect to pollution of the environment EN 1250-2 (1995) has to be mentioned, however, this is more or less only a modification of EN 84 and as such not very satisfactory. Evaporation tests started as late as in the 50th mainly in connection with fluorides and later with PCP. Examples for a standard to determine the remaining efficacy are the German Pre-Standard DIN 52172-3 (1971) and EN 73, based on the German standard and first published in 1978. A specific standard for emissions is EN 1250-1 (1995). The reflections presented in the paper consider evaporation as well as leaching tests where the general requirements and the statements to the kind of specimens and to the treatment apply to both types of emissions at the same time. For the test procedure itself, however, different methods are needed.
H Willeitner, R-D Peek


A comparison of the effectiveness of a vacuum oven and a wind tunnel in the accelerated ageing of treated wood by evaporation
1989 - IRG/WP 2334
R J Orsler, G E Holland


Stability and performance of tributyltin compounds
1984 - IRG/WP 3275
Based on the critical examinations of the disputable permanence of tributyltin compounds in wood, this paper deals with a number of examinations of the relative evaporation, thermal stability and oxidation stability of some TBT-compounds. While thermal and oxidative stability is high for all TBT-species, the relative evaporation at elevated temperature is highly variable, and lowest for the TBT-esters examined. Evaporation measurements on treated wood confirm this order of precedence and stress the importance of the preservative formulation. The results also indicate that TBTO evaporates 2-3 times faster than TBTN. It is established that at high retention of TBT in wood the decomposition is slower than at low retention. This fact combined with the extra high retention of TBT in vacuum treated joints of window frames explains the fine record of non-failure for such windows, and the paper ends up with a calculation indicating the presence of sufficiently high amounts of tributyltin for effective fungicidal protection of Nordic class B impregnated windows for at least 20 years.
F Imsgard, B Jensen, H A B Landsiedel, H Plum


The potential for accelerated ageing to determine the persistence of active ingredients in timber
2006 - IRG/WP 06-20323
Fast screening methods for evaluating the persistence of active ingredients in timber are proposed. This is an outline proposal which is intended to provoke discussion and further development of the methods. Reliable and accurate analytical methods are key to these tests.
L D A Saunders, M R Powell


Volatile losses of wood preservatives
1973 - IRG/WP 236
The purpose of the work we have undertaken so far has been to try to quantify the volatile losses which occur in treated timber, and to examine some of the factors which influence these losses. The preservative compound chosen for the initial part of the programme was the contact insecticide g-BHC. This was attractive for several reasons, not the least of which was that specific and sensitive analysis was possible using gas-liquid chromatography. In addition to this, g-BHC is of major importance in insect control in both pre-treatment and remedial treatment, the latter frequently being subject to a written guarantee.
J W W Morgan, D F Purslow


Risk of pulmonary damage as a result of an evaporation of ca. 50 ppb = 42 mg HF, evaporated from wood treated by difluorides
1987 - IRG/WP 3401
In this review of the literature the effects of fluorides and fluorine on man are described, especially the low level effects of inhaled HF on human beings. The term "fluoride" is used as a general term everywhere, where exact differentiation between ionic and moluecular forms or between gaseous and particulate forms is uncertain or unnecessary. The term covers all combined forms of the element, regardless of chemical form, unless there is a specific reason to stress the gaseous elemental form F2, in which case the term "fluorine" is used.
H F M Nijman


Assessing the importance of degradation mechanisms on the loss of effectiveness of wood preservatives
2000 - IRG/WP 00-20193
Accelerated ageing systems developed for application to samples in the laboratory prior to biological tests, should reflect those natural deterioration processes that are likely to occur in the hazard classes defined in EN 335-1. Losses through evaporation or the effects of leaching have been recognised, however their importance, relative to other mechanisms has not been quantified. Degradation mechanisms including photolysis, thermolysis and hydrolysis have largely been ignored. This paper presents information from a study, conducted as part of a project supported by the European Commission (SMT4-CT96-2135), on the relative importance of these different mechanisms through a series of experiments using model compounds. These model compounds were selected because they have known susceptibility to one of the identified degradative mechanisms. TnBTO has been used to monitor photolysis, trihexylene glycol biborate to examine the effects of hydrolysis and lindane to monitor evaporation. The experimental data are compared to semi-natural exposure data. Support for ensuring that the various degradative mechanisms occur in the accelerated ageing systems is recommended.
E D Suttie, R J Orsler, T Dearling


Creosote losses due to ageing methods prior to laboratory efficacy testing
2002 - IRG/WP 02-20256
Laboratory efficacy testing of creosote is affected by the impact of volatile components on the fungal growth. European test methods for assessing efficacy against Basidiomycetes and soft rot fungi is based on two standard methods, EN 113 and ENV 807 respectively. Combined with both fungal tests two pre-treatment methods are commonly used, namely EN 84 (leaching) and EN 73 (evaporation). Within the activities of the European research project "WOODPOLE" the impact of both ageing methods has been compared with several alternative methods using a gravimetric approach. The three creosote types defined by the Western European Institute for wood preservation (WEI) as types A, B and C have been used to treat wood blocks as in EN 113. Mass loss due to ageing revealed not only the importance of the diluting solvent used but also the impact of the creosote type. Since both EN 84 leaching and EN 73 evaporation proved to eliminate a considerable part of the absorbed creosote mass, it is suggested that prior to laboratory fungal testing for hazard class 4 applications (EN 335) a consecutive ageing of evaporation and leaching according to the existing standards should be applied. The conclusion that we came to and have used in the subsequent testing was that two different methods of ageing should be performed for Basidiomycete and softrot testing i.e. (1) for EN 113 ageing the EN 73 evaporation (12 weeks wind-tunnel exposure) and the EN 84 leaching after open air ventilation; and (2) for ENV 807 the initial ageing is based on EN 73 evaporation in the wind-tunnel, or a 12 weeks open air ventilation prior to the required EN 84 leaching.
J Van Acker, K Ghekiere, M Stevens


Artificial weathering exposure as an alternative for standard ageing according to EN 84 (leaching) and EN 73 (evaporation)
2002 - IRG/WP 02-20254
In order to verify potential weaknesses of wood preservatives fungal tests are carried out after ageing of wood preservative treated test blocks. The European standard EN 599 as a framework for efficacy assessment of wood preservatives includes the use of two ageing methods prior to fungal testing, namely a leaching method (EN 84) and an evaporation method (EN 73). The European research project "F.A.C.T." aimed amongst other objectives to provide in more realistic alternatives for both ageing methods. Artificial weathering systems generally used to assess the weathering resistance of exterior coatings was looked at as an alternative. For this purpose artificial weathering devices were selected which besides a control of temperature and light also allow for the impact of moisture by means of water spraying. UV cabinets with spray option were used to evaluate the effect of ageing of three wood preservatives: a waterborne Cu-HDO preservative, an oilborne triazole combination and a TBTO reference preservative. Based on EN 113 Basidiomycete testing of aged specimens a range of equivalent UVS systems proved to be suitable as an alternative ageing system prior to EN 84 and EN 73.
J Van Acker, M Grinda, D J Dickinson


Kiln drying of LSOP treated timber: rate of solvent evaporation, overpaintability and recovery of the solvent
1992 - IRG/WP 92-3711
The rate of solvent evaporation from LOSP treated timber dried in a kiln at 35°C has been investigated. Around 50% solvent removal has been found to be consistent with good overpaintability using a water based acrylic primer. It has been demonstrated that an activated carbon solvent recovery system is capable of removing all the solvent vapour from the outlet of a commercial joinery drying kiIn, that the solvent is subsequently recoverable using steam and that the recovered solvent is suitable for re-use.
P Warburton, L B Sheard


Evaporation and redistribution of creosote in pine poles during storage
1996 - IRG/WP 96-50064
During the work with European standards for pressure treated wood, it has been questioned if the lapse of time between impregnation and chemical analysis of the retention is critical, especially for creosote. "The Norwegian Control Scheme for Preservative Treated Wood" has not discovered any retention problems analysing CCA preservatives in wood. If the lapse of time between impregnation with creosote and extraction of the creosote in bore cores was within two months, the retention normally met the requirement. If the lapse of time was more than two months, we usually got a lower retention than required. At the control we always take our bore core samples from the upper part of horizontal stored poles. The bore cores are stored for about two days in test tubes sealed with a plastic stopper. In this investigation we analysed the amount of creosote in 2 meter long poles (by extraction described in AWPA A6) at various time intervals during storage for 30 months. We analysed the remaining creosote both in the upper and in the lower horizontal part of the poles. The redistribution found by extraction from the upper to the lower part in the poles during storage was 15-20%. In addition we found in the same period an evaporation of about 10% from the poles.
F G Evans, B Nossen