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A novel lipid-related compound, (Z)-1,7-nonadecadiene-2,3-dicarboxylic acid, produced by white-rot fungus Ceriporiopsis subvermispora
2001 - IRG/WP 01-10411
Lipid peroxidation is a possible oxidative process of lignin-degradation at a site far from the enzymes by selective white rot fungi. Production and peroxidation of saturated and unsaturated fatty acids by Ceriporiopsis subvermispora strongly suggests involvement of lipid peroxidation in its ligninolytic system. In this paper, a new aliphatic lipid-related fungal metabolite was isolated from wood meal cultures of C. subvermispora and its chemical structure was fully identified. The novel compound was identified as (Z)-1,7-nonadecadiene-2,3-dicarboxylic acid, an itaconic acid derivative linking a hydrophobic hexadecenyl group at the C-3 position of the core structural unit.
M Enoki, Y Honda, M Kuwahara, K Messner, T Watanabe


The effect of temperature on the rate of fixation of an alkyl ammonium compound (AAC) wood preservative
1984 - IRG/WP 3293
The rate of fixation of an alkyl ammonium compound wood preservative was measured by soaking samples of wood wool in various preparations of the preservative for arbitrary times followed by immediate leaching in water. The wood wool was then analysed for residual preservative. The results indicated that fixation was very rapid and increased at higher temperatures.
P Vinden


Calculation of preformance index of Bardac 20 (an alkylammonium compound) evaluated in a field stake test
1982 - IRG/WP 3206
Bardac 20 treated stakes have been in test for three years at the Westham Island test site near Vancouver, B.C. The Performance Index for the preservative was calculated and found to be 0.009 which infers that, at the standard retention, Bardac 20 added 0.9 y to the life of the stake. It may be concluded that when tested using a standard field stake test using ponderosa pine (Pinus ponderosa Laws) sapwood at a standard retention of 6.35 kg/m³ Bardac 20 did not fulfil the expectations indicated from the laboratory screening test conducted earlier. Studies are in progress to determine the cause of this discrepancy in performance with a view to improving this class of compound as a wood preservative for use in ground contact situations.
J N R Ruddick


Evaluation of an alkyl ammonium compound as a fungicide to control sapstain and mould during diffusion storage
1984 - IRG/WP 3282
An alkyl ammonium compound ('Akzo' ES 255) was evaluated for its effectiveness against mould and sapstain during diffusion storage of boron-treated rubber wood. Though ES 255 at 1.0% concentration was effective against mould (71%) and sapstain (89%) it is less satisfactory compared to 0.5% sodium pentachlorophenoxide against mould (92%) and sapstain (98%).
R Gnanaharan


Reaction of osmium tetroxide with a diphenolic compound as a model substance for demethylated lignin
1986 - IRG/WP 1303
By using caffeic acid as a model substance for diphenolic moieties of demethylated lignin it was found that electron dense particles called by the authors "osmiophilic particles" in former papers are reaction products of OsO4 with the model substance. By these products it is possible to indicate the enzymatic demethylation of lignin taking place during wood decay. The appearance of the electron dense particles in decay patterns described in earlier papers is briefly summarized.
K Messner, E Srebotnik


Chapter 6 - Preservatives of bamboo
2007 - IRG/WP 07-10635-06
Almost all currently available oil-borne, water-borne and compound types of preservatives suitable for the preservation of bamboo or wood have been described along with their classifications, applications, formulations, merits and demerits, history of invention or discovery and development. The preservatives suitable for wood are also considered suitable for bamboo.
A K Lahiry


Adsorption of ACQ and CuMEA Wood Preservatives in Red pine
2005 - IRG/WP 05-30374
The rates of stabilization or fixation of ACQ subcomponents (CuO, DDAC and MEA) in red pine (Pinus resinosa) were compared for different solution concentrations (0.75%, 1.5%, 2.25% and 3% ACQ-D) and post treatment conditioning temperatures. Preservative solutions were impregnated into red pine sapwood by a full-cell treatment. Copper and MEA adsorptions from copper monoethanolamine solutions without DDAC were also evaluated for comparison. After the treatments, samples were conditioned without drying either at 22° C for seven weeks or at 50° C for one week. At different times after treatment, expressate from the specimen blocks was analyzed for copper, DDAC and MEA. Copper and MEA adsorption by the wood cell walls followed similar trends. The equilibrium copper adsorption ranged from 44% at high ACQ retentions to about 95% for the lowest retention while the values in the CuMEA system were slightly higher for the higher retentions, ranging from about 54% to 93%. This suggests that DDAC may compete with CuMEA for reaction sites at high ACQ concentrations. Adsorption of DDAC into the wood cell wall matrix was rapid; at all solution concentrations, more than 80% of DDAC was adsorbed by red pine sapwood within minutes after treatment.
C Tascioglu, P A Cooper, Y T Ung


Marine trials with water-borne salts and organotin compound
1986 - IRG/WP 4128
Pinus sylvestris blocks treated with water-borne salts (CCA, CCB, CCF) and organotin compounds (TBTO, TBTCl) were submerged in the sea at Follonica station. The results obtained after 12 years of immersion are presented. The samples treated with CCA, CCB and CCF at the lowest concentration (2%) were destroyed after 7-9 years and the samples treated with CCB and CCF at the highest concentrations (4%, 6%), which were tested for a longer time than CCA treated samples, were destroyed after 11-12 years. The samples treated with organotin compounds did not show any attack by molluscan borers after 12 years with the exception of those treated with TBTCl at the lowest concentration (0.5%). The organotin compounds were less effective against crustacean borers.
A Gambetta, E Orlandi


Leachability of didecyldimethylammonium chloride (a quaternary ammonium compound) from four wood species
1982 - IRG/WP 3204
Sapwood blocks prepared from red pine, ponderosa pine, southern yellow pine and hem-fir (a commercial mixture of western hemlock and amabilis fir) were treated with didecyldimethylammonium chloride, (an alkylammonium compound, AAC). After oven drying the blocks were vacuum impregnated with distilled water and subjected to a static leach cycle for 48 hours. The leachate was analyzed and the amount of AAC which leached from each wood species, calculated. The results showed that the leaching of didecyldimethylammonium chloride from ponderosa pine was not unusual, and that the amount of AAC leached for the various wood species increased in the order > red pine > ponderosa pine > southern yellow pine > hem fir.
J N R Ruddick, A R H Sam


Movement of water through quaternary ammonium treated wood
1987 - IRG/WP 3440
Radiata pine sapwood stakes were treated with didodecyl methyl 1, 3 dichloropropenyl ammonium chloride and distearyl dimethyl ammonium chloride. Various ratios of these two chemicals were, tested to determine the extent of water movement through the treated wood. Measurements were taken of the amount of water moved through the wood, degree of wetting of various sectors of the stakes, and the distribution of the quaternaries through the stakes. The results showed that didodecyl methyl 1,3 dichloropropenyl ammonium chloride increased the amount of water movement through the stakes compared to untreated, however the addition of distearyl dimethyl ammonium chloride reduced the water movement to below that of untreated. Over the twelve weeks of the trial no redistribution of quaternaries was noted.
P J Hayward, J Duff


Decay and termite resistance of wood treated with boron-containing quaternary ammonia compound, didecyl dimethyl ammonium tetrafluoroborate (DBF) incorporated with acryl-silicon type resin
2004 - IRG/WP 04-30334
This study evaluates the decay and termite resistance of surface-treated wood with didecyl dimethyl ammonium tetrafluoroborate (DBF) incorporated with acryl-silicon type resin emulsion. DBF is a quaternary ammonia compound and contains boric tetrafluoride (BF4-) as a counter ion in its chemical structure. In the study, DBF was incorporated with an acryl-silicon type resin to increase water-resistant of the preservative solution, and, in turn, to increase decay and termite resistance of surface-treated wood after severe weathering processes. Laboratory decay resistance tests were performed using brown-rot fungus Fomitopsis palustris and white-rot fungus, Trametes versicolor. Treated wood specimens were also subjected a 3-week-termite resistance tests using subterranean termites, Coptotermes formosanus. Wood specimens surface-treated with preservative solution including 2% DBF and the resin showed decay resistance against both F. palustris and T.versicolor even after severe weathering. Results suggested that treatment with DBF at 2% or greater concentrations containing acryl-silicon type resin emulsion would protect wood used outdoors against both fungal decay and termite attack.
S N Kartal, W J Hwang, K Shinoda, Y Imamura


New principles for the protection of wood: Impregnation with waterborne resins
1995 - IRG/WP 95-40047
The environmental impact of classical wood preservatives as well as the use of tropical wood species with high natural durability is regarded increasingly critically in the public. Therefore other partially new principles for the protection of wood, like chemical modification, or treatment with resins were examined especially in USA, Japan and in Europe with promising results predominantly in the lab scale. The work to be presented is focused on the feasibility to upgrade wood by a wide spectrum of water-borne resins under practical conditions of processing. The chemicals examined range from purely physically effective resins by hydrophobation and mechanical blockage up to such promising a chemical modification by their reactive groups. The behaviour of the resin solutions in a pressure process as well as the penetration parallel and orthogonal to the grain were investigated. Further, resin-uptake, improvement of hardness, and dimension stability, were examined. SEM studies are intended to show penetration pathways and linkage of the resins to the cell wall. Running tests on the investigation of the resistance against basidiomycetes and softrot fungi are not yet completed.
A O Rapp, R-D Peek


Fungicidal effectiveness of amended alkylammonium compound
1987 - IRG/WP 3421
Amendment of didecyldimethylammonium chloride was attempted to improve its fungicidal effectiveness and properties of treating solutions. Addition of copper definitely increased effectiveness in controlling wood decay fungi, although metal corrosiveness and stability of treating solutions was unsatisfactory. Further amendment with stabilizer(s), anticorrosive agent(s) and sequestering agent(s) resulted in improving fungicidal effectiveness as well as properties of treating solutions. When a wood block was impregnated with an adequate mixture of didecyldimethylammonium chloride, copper sulphate, sequestering agent, stabilizer and anticorrosive agent (1:0.5:0.5:1:0.25), laboratory test (JIS A 93029) indicated that a lower retention level of didecyldimethylammonium chloride (1.1 kg/m³) gave a satisfactory protection to the block from decay fungi. On the other hand, didecyldimethylammonium chloride itself was effective enough at higher retentions of 2.2-4.3 kg/m³.
K Tsunoda, K Nishimoto


Evaluation of polymeric alkylphenol polysulfide as a new wood preservative compound
2000 - IRG/WP 00-30251
At the 30 th IRG meeting held in Rosenheim, Bavaria, Germany, we reported on a Polymeric Alkylphenol Polysulfide (PXTS) which shows potential as a new non-leachable, environmentally compatible wood preservative compound exhibiting excellent biocidal efficacy. Comparative soil-block test results showed that PXTS was twice as effective as Creosote when evaluated against both white- and brown-rot fungi, including the creosote tolerant fungus, Neolentinus lepideus. Additional data collected from the laboratory soft-rot test and field stakes continue to verify the efficacy of this compound. After 20-months exposure in a soil bed soft-rot test, PXTS appears to be approximately four times as effective as creosote. After 18 months exposure all of the field stakes are in excellent condition. The results of a battery of standard toxicological test protocols conducted recently look promising and further tests are being carried out in conjunction with relevant governmental regulatory agencies. Some preliminary laboratory decay test results for a modified PXTS formulation look promising and additional tests with this material have been initiated.
J Goswami, A Abramson, R Buff, D D Nicholas


Effect of test site location on in-ground preservative performance after 6 years
2001 - IRG/WP 01-20231
Pinus radiata test stakes were treated with 4.1 kg/m3 of CCA and Fagus sylvatica with 6.1 kg/m3 of CCA. Both wood species were also treated with a copper plus triazole preservative (3 kg/m3 of copper) and chlorothalonil plus chlorpyriphos in oil (4.8 kg/m3 chlorothalonil). Furthermore, P. radiata was treated with ammoniacal copper plus a quaternary ammonium compound (2.6 kg/m3 copper) and a 60/40 mixture of high temperature creosote plus oil (61 kg/m3 creosote). Treated and untreated stakes were exposed in the ground at 13 sites in New Zealand and Australia for approximately 6 years. Preservative performance was significantly affected by site and there was a site-preservative interaction effect where decay hazard at a given site was dependent on preservative treatment. For pine, chlorothalonil plus chlorpyriphos, copper-azole and ACQ gave at least equivalent performance to the reference standards creosote and CCA, after approximately 6 years, at the majority of test sites. For beech, chlorothalonil plus chloropyriphos and copper-azole both gave superior protection to CCA, at the majority of test sites. In general, the results suggest that it is possible to select 3 - 4 sites that collectively pose a diverse decay hazard, representative of the majority of situations encountered by wood in service.
R N Wakeling


Polymeric alkylphenol polysulfide - A new wood preservative compound
1999 - IRG/WP 99-30193
The three most widely used preservative compounds are Chromated Copper Arsenate (CCA), Pentachlorophenol (PCP) and Creosote (which is a mixture of phenolic compounds). These preservatives are very effective but their long-term future use is questionable because of environmental concerns. These concerns have resulted in restrictions in usage and in some countries a ban on their use as wood preservatives. Consequently, there is a need for new wood preservative chemicals that have low mammalian toxicity and are environmentally friendly. In addition to phenolic compounds, sulfur compounds are extensively used in agriculture as herbicides and insecticides. Therefore, it was surmised that compounds containing both phenol and sulfur moieties would have potential as wood preservatives. In order to provide permanency, oligomeric or polymeric forms of these compounds are highly desirable in order to prevent preservative loss during treatment as well as from wood either by volatilization and / or by leaching. The excellent performance properties of the polymeric alkylphenol polysulfides as environmentally-benign wood preservative compounds to protect wood from wood decay fungi will be exemplified in this article by a representative compound currently under research and development - Polymeric Xylenol Tetrasulfide (PXTS). Monomeric phenol/ sulfur compounds have applications as vulcanizing agents (Wolf, 1946), as anti-oxidants for rubbers and plastics (Anon. 1986), as antibacterial additives in the form of bithionol or fenticlor and trihalogenated phenol for paints and wooden articles (Anon. 1990a), as delayed release antibacterial agents comprised of an inclusion compound of hinokitiol with a bisphenol (Anon. 1990b), and as bactericidal and fungicidal composition prepared from a mixture of chlorhexidine, trihalogenated phenols and phenylphenols ( Anon. 1990c). In addition, Asakura et al. (1989) reported on the anti-oxidant effect and antimicrobial activity of phenolic sulfides wherein the sulfur is attached to the alkyl side chain. Michael addition and radical addition reactions of ethanethiol and ethanedithiol with o-, m- and p-vinylphenol were used to prepare these phenolic sulfides. Gabler et al. (1974) reported that certain bisphenol compounds linked together with a thio bridge are highly active fungicides having a broad spectrum of activity.
J Goswami, A Abramson, R Buff, D D Nicholas


The effect of soil pre-exposure on the results of laboratory Basidiomycete testing
1991 - IRG/WP 2385
Scots pine sapwood blocks were treated with several concentrations of copper chrome arsenic (CCA), copper chrome boron (CCB) and a copper modified quaternary ammonium compound (CMAAC). Leached and unleached samples were exposed in a basidiomycete monoculture test using Coniophora puteana, a copper tolerant brown rot. Prior to testing half of the blocks were buried in unsterile soil for 4 weeks. The soil pre-exposure had little effect on the performance of the CCA and CCB treated samples against the brown rot but the performance of the CMAAC treated samples improved greatly
S M Gray


Biological test, AAS and EPR study of copper monoethanolamine complex with quaternary ammonium compounds as a wood preservative
2003 - IRG/WP 03-30321
Experiments were carried out on the wood preservative with a strong fungicidal activity based on Cu(II) carbonate, 2-aminoethanol (monoethanolamine) and quaternary ammonium compound (QAC). The object of the performed investigations was sapwood of Scots pine (Pinus sylvestris L.) treated with Cu-EA-QAC formulation. Mycological investigations were carried out according to EN 113 and EN 84 standards. The retention of the copper ions in the wood grows nonlinearly with concentration (in %) of the impregnating solution from 0,25 kg/m3 at 0.03% to 1,55 kg/m3 at 0.21% (i.e. nearly 6 times) whereas the copper leachability decreases 2,5 times from 15% to 6% in the same range. These results indicate good fixation of the copper to the wood and high leaching resistance. EPR results and computer simulations of the observed EPR spectra shows that in Cu-EA aqueous solution the Cu(EA)2(H2O)2 complexes exist and the main coordination plane is not destroyed in impregnating solution and in the wood. In Cu-EA-QAC-BA solution the Cu(EA)2(QAC)2 complexes appear whereas EPR spectra of the treated wood indicate coexistence of a few types of Cu-complexes. We have identified strongly fixed Cu(EA)2O2 and Cu(EA)2O complexes with oxygens atoms from wood functional groups.
B Mazela, I Polus, S K Hoffmann, J Goslar


Preliminary evaluation of new quaternary ammonia compound, didecyl dimethyl ammonium tetrafluoroborate for preventing fungal decay and termite attack
2005 - IRG/WP 05-30375
This study evaluates the decay and termite resistance of wood treated with didecyl dimethyl ammonium tetrafluoroborate (DBF), a recently developed quaternary ammonia compound containing boron. DBF contains boric tetrafluoride as a counter ion in its chemical structure. Laboratory decay resistance tests were performed using brown-rot fungus, Fomitopsis palustris and white-rot fungus, Trametes versicolor. Treated wood specimens were also subjected a 3-week-termite resistance tests using subterranean termites, Coptotermes formosanus. Decay resistance tests showed that wood specimens treated with 0.5 and 1.0% DBF solutions were well protected from both fungi even after a 10-day severe weathering process, suggesting the adequate fixation of DBF in wood. DBF treatment at 0.1% concentration was efficient against subterranean termites, Coptotermes formosanus Shiraki based on weight losses in both weathered and unweathered wood specimens. These results suggested that DBF could be used effectively to protect wood used outdoors against both fungal decay and termite attack and discolorations by fungi.
S N Kartal, W J Hwang, Y Imamura


FTIR studies on the weathering of didecyldimethylammonium compound (DDAC) treated wood
1993 - IRG/WP 93-30013
Wood treated with alkylammonium compounds (AACs), such as DDAC, weathered more rapidly than untreated wood. In order to examine the influence of DDAC treatment of wood on its weathering, treated and untreated microtomed sections of southern yellow pine earlywood of various thicknesses, were prepared and weathered for approximately one month. The changes in these samples were monitored using FTIR. The spectra of DDAC-treated samples showed that the treatment caused the lignin band at 1510 cm-1 to split and decrease in intensity due to chemical interaction between the preservative and lignin. FTIR spectra of the weathered samples confirmed that the removal of lignin and formation of carbonyl groups were greater for DDAC treated samples than untreated controls.
R Liu, J N R Ruddick


The effect of stack height on the performance of preservatives used for the prevention of sapstain on seasoning wood
1997 - IRG/WP 97-10192
The performance of three anti-sapstain preservatives was investigated under field conditions in south east England. The preservatives under test were: copper-8-quinolinolate (Mitrol PQ8) trimethylalkylammoniumchloride and sodium hexanoate (Sinesto B) and chlorothalonil (Tuff Brite). The preservatives were tested on Corsican Pine grown in south east England. The field trial was set up to investigate the robustness of the field trial protocol laid down as part of a collaborative European research project. Treated boards were close stacked and were assessed at 12, 18 and 24 week intervals. The test preservatives varied in efficacy: copper-8-quinolinolate (Cu-8) performed better than the quaternary ammonium compound (Quat) and chlorothalonil. However, very little mould colonisation occurred on the chlorothalonil treated boards compared with the boards treated with the other anti-sapstain preservatives. Observations also indicated that mould fungi were more prevalent on the upper boards of the top packs and that sapstain was heaviest on the bottom boards of the packs for all treatments. The results clearly showed that the height of the stacks had an effect on the infection pathways of colonising fungi and timber closer to ground level was clearly exposed to the greatest hazard. Statistical analysis supported this observation. Comparative field trials assessing antisapstain preservative performance should be set with the test stacks in a single layer at ground level.
J R Williams, D J Dickinson, J F Webber


Some textile auxiliaries as wood protective agents
2007 - IRG/WP 07-30417
This study evaluated some textile auxiliaries applicable for wood protection. Commercial alkoxysilane quarternary ammonium formulation and fluorocarbon based water-oil repellent were tested for their ability to provide hydrophobicity and antifungal effect to solid wood samples. Scots pine (Pinus sylvestris L.) sapwood samples were impregnated with 25, 50 and 100 % concentrations of the above mentioned compounds and cured in an oven at 80 ?C for 24 h. Water absorption rate (WAR), anti-shrink efficiency (ASE) and compression strength parallel to grain of the wood samples were determined. Biological resistance of leached and unleached wood samples against fungal decay was evaluated with a modified soil block test using Postia placenta. Fluorocarbon based water-oil repellent and alkoxysilane quarternary ammonium treated samples demonstrated some improved durability against decay fungi and anti-shrink efficiency compared to the untreated controls. The water uptake of treated wood was significantly reduced, especially after the treatment with alkoxysilane quarternary ammonium. The initial water repellence was well pronounced with the both tested chemicals, but after a longer submersion time (2 weeks), the reduction in water uptake was significantly diminished. No significant decrease of the compression strength parallel to grain of wood samples was monitored. Although the improved durability of wood treated with the tested formulations, the performance is far poorer than that of the commercially available copper-based formulations.
E Dizman, A Temiz, N Terziev, Ü C Yildiz


Quercetin - a potential compound of Azadirachta indica A. Juss. (Neem) leaves exhibiting activity against wood decaying fungi and termites
2008 - IRG/WP 08-30463
Azadirachta indica A.Juss. is widely recognized for its medicinal, insecticidal, pesticidal and anti-microbial property. Methanol extract of neem leaves revealed marked anti-fungal activity when subjected to malt-agar and soil block bioassay against wood destroying brown (Oligoporus placentus) and white rot (Trametes versicolor). The extract also revealed marked termicidal property when subjected to wood destroying termites i.e. Microcerotermes beesoni Synder in laboratory and against Odentotermes obesus Rambur in termite mound. Column chromatography of methanol extract resulted in isolation of compound exhibiting potential activity against fungi. The compound obtained was identified as flavanoid and structure elucidation was done by UV-Visible, IR, Mass, 1H & 13C NMR. The compound was identified as quercetin. It was further tested at 5µg concentration exhibiting 100% growth retardation of the test fungi.
S Dhyani, S Tripathi


Modification of Wood by a Water-Repellent Compound Used in the Textile Industry: Boron Release and Termite Resistance
2009 - IRG/WP 09-40447
In the study, wood specimens were treated with disodium octoborate tetrahydrate (DOT) and a commercial water and oil repellent compound, FORGUARD M®, a weak cationic emulsion containing dipropylene glycol monomethylether, water and solids in its formulation and used in the textile industry. There were two different processes for preservative treatments: double and single treatments. The leaching process was conducted according to Japanese Industrial Standard (JIS) K 1571. Leachates sampled from the leaching cycles for 10 days and extracts from the treated wood were analyzed with an ICP spectrometry. Contact angle measurements were also done for water-repellent properties of modified wood. Specimens were exposed to the subterranean termites, Coptotermes formosanus Shiraki, in laboratory conditions. Modification resulted in nearly 50% less boron leaching in both single and double treatments at 0.5 and 1% DOT concentration levels in comparison with DOT-only treated specimens. More boron release was seen in the specimens treated with 0.1% DOT and FORGUARD M® when compared to 0.5 and 1% DOT + FORGUARD M® treatments. Contact angles increased from 56 degrees exceeding 100 degrees in modified wood specimens. All unleached specimens showed perfect protection against termites; however, mass losses in control specimens and leached specimens were nearly 30%. After modification of wood treated with 0.5 and 1% DOT and FORGUARD M®, about 50% of total boron remained in these specimens after leaching course increased termite resistance of modified wood. In general, the termite mortalities were in good accordance with the mass losses that occurred in the specimens.
S N Kartal, E Terzi, B Erilkun, Y Imamura


Weathering of Wood Modified with the N-Methylol Compound 1,3‑dimethylol-4,5-dihydroxyethyleneurea (DMDHEU)
2009 - IRG/WP 09-40467
Scots pine (Pinus sylvestris L.) sapwood boards were treated with a methylated 1,3‑dimethylol-4,5-dihydroxyethyleneurea (mDMDHEU) causing weight gains of approx. 25% and exposed to weathering for 18 months. Compared to untreated boards, treatment with mDMDHEU reduced surface discoloration mainly caused by staining fungi. Boards treated with mDMDHEU exhibited clearly lower moisture content throughout the exposure time and lower water uptake in periodical submersion tests. The treatment also reduced deformation (cupping) and crack formation of the boards due to weathering (assessed as waviness and surface roughness). When coated boards were compared, prior treatment with mDMDHEU resulted in lower water uptake in periodical submersion tests, less discoloration, minor deformation (cupping) and less crack formation (assessed as waviness and surface roughness). Oil-based coatings did not peel off the mDMDHEU treated board surfaces as observed for the untreated board surfaces. Scots pine veneers were modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) to weight percent gains (WPG) of 10, 27 or 48% and exposed to artificial weathering. Initially, weight losses of unmodified veneers were significantly greater than those of DMDHEU treated specimens. The weight losses of all treated veneers during 144 h of weathering, however, were similar to those of the unmodified controls. Scanning electron microscopy revealed that DMDHEU treatment was highly effective at preventing the degradation of the wood cell wall during weathering. Tracheids in unmodified veneers became distorted within 48 h of weathering exposure, whereas cells in modified veneers, especially those reacted to higher weight percent gains, retained their shape even after 144 h weathering.
C Mai, Yanjun Xie, A Krause, K Urban, P D Evans, K Richter, H Militz


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