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The effect of additives on copper losses from alkaline copper treated wood
2007 - IRG/WP 07-50246
The replacement of chromated copper arsenate (CCA) by alkaline copper compounds has heightened awareness of the potential impact of copper losses on aquatic organisms. While there remains a healthy debate concerning the actual risk of copper leaching from wood preservatives into aquatic ecosystems, it is clear that reducing these losses will be necessary to avoid continued regulatory actions against the use of preservatives in these environments. While post-treatment processing and coatings can reduce losses, neither is completely effective. Another alternative is to add compounds to the alkaline system to complex or otherwise reduce copper losses, much in the same way that chromium acts in CCA. One possible additive is Di(hydrogenated tallowalkyl) dimethyl ammonium chloride, also know as 2HT, which is a common fabric softener. Preliminary tests suggested that this compound reduced copper losses from alkline copper quat and, in doing so, improved overall biological performance. In this report, we describe additional trials to assess the effect of 2HT on copper migration from wood treated with either ACQ or copper azole (CA). 2HT had a variable effect on copper migration, but was associated with reduced copper losses in some treatment combinations. Further trials are underway to assess the biological efficacy of wood treated with combinations of 2HT and either ACQ or CA.
J Mitsuhashi, J J Morrell, L Jin, A F Preston
Three-year field test of preservative-treated Canadian species in Korea
2014 - IRG/WP 14-30646
The purpose of this study was to generate field performance data in Korea on Canadian softwood species preservative-treated to Canadian standards. Two field tests of preservative-treated Canadian softwood species, one in ground contact and one above ground, were installed in Jinju, Korea in November 2010. Western hemlock and white spruce were incised and pressure-treated with alkaline copper quaternary (ACQ) or copper azole (CA), based on the Canadian CSA O80 Series-08 standards. End-matched material for ground contact exposure only was also installed in September 2011 at a field test site in Canada. After three years of exposure in Korea and two years in Canada, no decay was found in preservative-treated samples at either test site, while in untreated material decay, and particularly termite attack in Korea, were well advanced.
Jieying Wang, Jong Bum Ra, P I Morris
The influence of previous anti-blue-stain preservative treatments on the fixation of CC in spruce
1997 - IRG/WP 97-30134
Freshly cut and kiln dried spruce boards were treated with 4 different anti-blue stain preservatives (ABP). After a period of 10 days allowing the samples to dry and fixate, the samples were treated with CC (chromium, copper formulation) using a vacuum pressure cycle. After impregnation the wood was steam fixed. A submersion leaching test showed differences in the leachable quantity of copper and chromium. When related to the retention of both salts after impregnation, no differences could be found between samples previously treated with anti-blue-stain preservatives and untreated samples. However, the retention of CC diminished significantly by application of quaternary ammonium compounds.
M Van der Zee, W J Homan
A field test with anti-sapstain chemicals on sawn pine timber in Finland
1986 - IRG/WP 3368
Fourteen formulations, each in two concentrations, were tested for effectiveness against sapstain, mould and decay on Scots pine (Pinus sylvestris L.) in a field test in South-Finland. The trial was commenced in June 1985 and finished in October 1985. During the test the boards were infected mainly by mould fungi. In kiln dried boards the protective effects of nine and in green boards of four treatments were better than the effect of the tested formulation of sodium chlorophenoxides at 1.5%
Natural exposure weathering tests: Their role in the assessment of wood preservative efficacy
1993 - IRG/WP 93-20006
Previous work has demonstrated the potential and usefulness of natural ageing procedures in e evaluation of wood preservative efficacy. This results from the combination of physico-chemical influences and microbiological interactions with both substrate and wood preservative. In this paper, results are presented for a range of biocide types. Discussions are centred on the value of natural exposure weathering tests for preservative efficacy assessment and the importance of biological persistence in the design of effective wood preservatives.
G R Williams, J Brown
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
Laboratory and field trials of novel antisapstain formulations
1997 - IRG/WP 97-30146
This document covers the results of laboratory and field trials of combinations of fungicides formulated using a patented technology (PCT NZ 96/00143). A 3 week laboratory trial that uses radiata pine (Pinus radiata D. Don) branch discs as a substrate was used to determine which combinations possessed a suitable spectrum of fungitoxicity against key sapstain, mould and decay fungi. In particular fungitoxicity against Ophiostoma piceae H & P Syd was looked for as this is the most difficult fungus to control on freshly cut radiata pine in New Zealand. The most promising formulations were then tested using block stacked radiata pine stored for 11 weeks during a high hazard summer period. In general the field trial results corroborated with the laboratory disc trial results. The importance of a broad spectrum of fungitoxicity and in particular a high level of activity against O. piceae, was shown by both types of trial. A formulation containing hexaconazole (0.014%w/v) plus carbendazim (0.028%w/v) plus a quaternary ammonium compound (0.291%w/v) was particularly promising. This formulation achieved significantly better (5% level of probability) control than the commercial standards, for 11 weeks of summer storage. The low fungicide concentrations used auger well for it's cost effectiveness. It is believed that this was in part due to fungicide synergy, broad spectrum activity and the use of microemulsions and solutions of the key fungicide components.
R N Wakeling, P N Maynard, D R Eden, C M Chittenden, B Carpenter
Performance of Paraserianthus falcataria treated with ACZA, ACQ, CC or CCA and exposed in Krishnapatnam harbour, India
2005 - IRG/WP 05-30382
Paraserianthus falcataria (=Albizia falcataria) treated to two retentions with ammoniacal copper zinc arsenate (ACZA), ammoniacal copper quaternary (ACQ), ammoniacal copper citrate (CC) and chromated copper arsenate (CCA) was assessed over 34 months in a tropical marine waters at Krishnapatnam harbour on the east coast of India. ACZA treatment showed comparatively better resistance than CCA, ACQ and CC, while CC provided the least resistance to marine borer attack. Eight species of borers i.e. Martesia striata, M. nairi, Teredo furcifera,T. parksi, Lyrodus pedicellatus, Nausitora hedleyi, Bankia campanellata and B. rochi were recorded on test panels. Of these, M. striata, L. pedicellatus, T. furcifera and B. campanellata were the dominant species, while other species settled sporadically. The results suggest that copper based preservatives are less likely to perform well under extreme tropical exposures without arsenic.
B Tarakanadha, K S Rao, J J Morrell
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
Working plan: Second international collaborative field trial
1995 - IRG/WP 95-20056
This paper describes the scope, objectives, and approaches to be used in the second international collaborative field trial approved by the Scientific Programme Committee for partial funding in 1994. The trial is designed to develop a broad data base on causal mechanisms, interactions, and factor affecting the performance of treated wood in ground contact. The trial encompasses 12 different field test sites representing all continents except Antarctica. Preservatives were chosen to represent new technologies and include oilborne, waterborne copper-organic, and water-dispersible systems. CCA is used as the reference system. Task forces to research the following areas are described: accelerated soilbed testing, decay types/modes of failure, preservative depletion, abiotic factors, and copper tolerance.
H M Barnes, T L Amburgey
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
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
Effects of sodium hypochlorite on compression strength and copper retention of spruce wood treated with copper azole and alkaline copper quat
2007 - IRG/WP 07-40362
This work investigates the effects of sodium hypochlorite on compression strength values and copper retention ratios of refractory spruce wood (Picea oriental L.) treated with the waterborne preservative Copper Azole, (CBA-A, Tanalith-E 3492) and alkaline copper quat (ACQ-2200). Before the copper azole and alkaline copper quat treatment, the samples were immersed in 500 ml of sodium hypochlorite solution for three different durations (2, 4, and 6 hours). A 2 % active ingredient solutions of CBA-A and ACQ were applied for use in vacuum treatment of the sapwood samples. Average copper contents of the specimens were higher than that of the control groups except of the 6-hours sodium hypochlorite treatment in ACQ impregnation. The highest copper value was seen in the variation the 6-hours sodium hypochlorite treatment in the CBA-A impregnation. Compression strength values generally slightly reduced compared to the control groups especially in ACQ impregnation.
S Yildiz, E Dizman, A Temiz, Ü C Yildiz
Micro-Distribution of Micronized Copper in Southern Pine
2008 - IRG/WP 08-30479
For copper-based preservatives to be used in ground contact, penetration of copper into the cell wall is believed to be important to protect the wood from soft rot fungi. Preservatives containing soluble copper are known to do this. It is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. An AWPA standard E11 leaching test found that leachate from southern pine blocks treated with a preservative containing particulate copper (Micronized copper quat) contained copper ions, suggesting that copper-containing particles in the treated wood slowly release mobile copper. Southern pine sapwood samples treated with wood preservatives containing soluble (ACQ-D) and particulate copper (Micronized copper quat), as well as untreated southern pine sapwood, were analyzed by Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-Ray Spectrometry (EDS). Copper was detected in the lumens of wood treated with both preservatives, and not in the untreated control. Moreover, the presence of small amounts of copper in the cell walls of samples treated with Micronized copper quat and ACQ-D was indicated by ESEM and EDS. This was further supported by the results of a fungal cellar test and a field stake test which demonstrated that wood treated with Micronized copper quat is resistant to soft rot attack. Future work will investigate copper mobility from particles lodged in the lumens.
R Stirling, J Drummond, Jun Zhang, R J Ziobro
Alkaline copper treated wood for use in residential decking
2008 - IRG/WP 08-30490
Alkaline copper quaternary ammonium compound (ACQ) treated decking was exposed in a field experiment and the mobile copper assessed based on that collected in the leachate. The amount of copper which leached was modeled after 4 years. The results showed that boards which leached most chemical initially provided the greatest loss over four years. The reduction in the mobility of copper with time was calculated and found to approach zero after about 11 years. The application of water repellant slowed down the loss of copper and could extend the mobile copper duration beyond that in control samples. The migration of copper onto check surfaces was confirmed with retentions exceeding that reported to protect wood above ground from spore germination by basidiomycete fungi.
J N R Ruddick
Corrosion of fastener and connector in contact with alkaline copper treated wood – it is a problem
2008 - IRG/WP 08-40437
For many decades, chromated copper arsenate (CCA) was the most common wood preservative used in North America for residential and industrial applications. Since December 31, 2003, the use of CCA for residential application was voluntarily terminated. One of the most widely accepted alternative wood preservatives in Western Canada is Alkaline Copper Quaternary Compound (ACQ). This paper will compare the corrosion data of CCA-treated wood with that of ACQ treated wood at a similar preservative retention. It also discusses the appropriate methodology for carrying out the corrosion studies. A modified draft American Wood Protection Association (AWPA) corrosion test method was used, where fasteners were sandwiched between two pieces of treated wood and exposed to the continuous water mist at an elevated temperature. All fasteners were tested for resistance of the coating to mechanical damage, prior to exposure. The study demonstrated that ACQ treated wood is indeed more corrosive than CCA treated wood. The study also showed that the application of water repellant to ACQ treated wood significantly reduced the corrosion rate. The best estimation of the corrosion rate was the measurement of the loss in the average core diameter in combination with a visual evaluation of the fastener and corrosion products.
J N R Ruddick
Comparison of laboratory and natural exposure leaching of copper from wood treated with three wood preservatives
2008 - IRG/WP 08-50258
Standard and non-standard laboratory and field leaching tests were used to compare copper leaching from wood treated to above ground and ground contact specified retentions for three wood preservative systems, CCA-C, ACQ-D and a micronized copper formulation with quat DDAC as co-biocide. Copper leaching was highest for the ACQ formulation. Percent leaching was lowest for the micronized copper system (MCQ) but amount of copper leached (mg/m2) was higher for MCQ than for CCA because of the higher copper content in the former formulation. The amounts of copper leaching varied considerably from test to test, but in most cases, the relative amounts of copper leaching from wood treated with the three formulations were consistent. One exception was the AWPA E20 soil leaching test which provided variable results, that showed that leaching of copper from CCA and MCQ samples was more similar to that from ACQ samples than observed for the other test methods. Also, the natural exposure tests (horizontal and vertical exposure) has less dramatic differences among the preservative systems.
P A Cooper, Y T Ung
Copper to quat ratio in alkaline copper quat (ACQ) wood preservative - Effects on fixation and leaching of preservative components in red pine
2009 - IRG/WP 09-30496
This study investigates the effect of the relative proportion of copper oxide (CuO) to didecy dimethyl ammonium carbonate (DDACb) in an alkaline copper quat (ACQ) formulation on the rate of copper fixation or stabilization and the resistance of treated wood to leaching of copper and quat (DDACb). Red pine samples were treated with ACQ, having CuO to DDACb ratios of 2:1 (the normal ratio for ACQ-D), 1:1 and 1:2, at concentrations of 0.6%, 1% and 1.5%. Treated samples were wrapped in plastic and post treated at 500C. Samples were squeezed to express solution, which was analyzed for copper to measure the percentage copper fixed at different times during post treatment conditioning. Conditioned samples were subjected to AWPA E11 laboratory leaching experiments and the amounts of copper and DDACb leached from the samples were analyzed. A decrease in relative proportion of copper in the ACQ formulation from a CuO to DDACb ratio of 2:1 to 1:1 and 1:2 resulted in a substantial reduction in the time required for the fixation of copper. There was a significant decrease in the amount of copper leached from the species studied with reduction of relative proportion of copper in the ACQ formulation. The reduction in leaching was higher for samples treated with concentrations of 1% and 1.5% ACQ compared to the sample treated with 0.6% ACQ. Formulation having 1:1 CuO to DDAC ratio appears to be the most promising, considering the positive effects of reduced copper ratio on copper leaching and fixation time and the minimal effect on DDAC leaching.
S Pankras, P A Cooper, T Ung, L Awoyemi
Re-Distribution of Copper in the Cell Walls of Wood Treated with Micronized Copper Quat
2009 - IRG/WP 09-30506
Wood treated with copper-based preservatives to be used in ground contact may fail to inhibit soft rot fungi if penetration of copper into the cell wall is insufficient. Preservatives containing soluble copper are known to penetrate the cell wall; however, it is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. A method was developed to accelerate and detect re-distribution of copper into the cell wall. Copper was found to re-distribute into the cell wall, presumably from cell lumen deposits, in both ACQ- and micronized copper quat-treated samples after exposure to high temperature and relative humidity. In a non-accelerated test, copper was not found to re-distribute into the cell wall in either ACQ- or micronized copper quat-treated samples after exposure in soil at 15°C for eight weeks.
R Stirling, J Drummond
Micronized Copper Preservative Systems: Observations on the Release of Cupric ion (Cu2+) from Treated Wood and Performance against Wood Decay Fungi
2009 - IRG/WP 09-30519
In an attempt to address the mechanism of action of micronized copper preservatives, a 20-week continuous water leaching study was conducted. The leaching results indicated that, once impregnated in wood, micronized copper preservatives continuously release cupric ion, and the levels of cupric ion released from micronized copper treated wood are higher than those released from CCA treated wood, and similar to those from ACQ-D treated wood with the exception of the first few leaching cycles. A 30-month soil bed fungal cellar test was also conducted, and the results revealed that micronized copper quat performed at least as well as ACQ-D against soft rot, confirming the presence of mobile cupric ion in the S2 layer of wood cell wall. In addition, two field stake studies of micronized copper preservatives were also conducted, and the results indicate that micronized preservative systems provide excellent long-term protection against wood destroying fungi and insects, and perform at least as well as ACQ-D.
J Zhang, R Ziobro
Adsorption of ACQ components in wood
2010 - IRG/WP 10-30522
To investigate the chemical adsorption capacity of copper-monoethanolamine (Cu-Mea) components on wood, the Na+ cation exchange capacity (CEC) of red pine (Pinus resinosa Ait.) was determined and compared to the adsorption capacity of free Mea and Cu-Mea complexes. The CEC increased with increasing pH. Free Mea adsorption as a function of pH followed the sodium adsorption curve except at pH over 9, when it exceeded the CEC. Cu-Mea adsorbed up to the CEC at pH 9.0-9.5 apparently as Cu(Mea)+, whereas the complex in solution is predominantly of the form Cu(Mea)2+. For the quaternary ammonium compound, alkyl dimethyl benzyl ammonium chloride (ADBAC) adsorption isotherm showed two different adsorption mechanisms into wood: ion exchange reaction at low concentration and hydrophobic interaction at high concentration. ADBAC adsorbed at solution concentrations below a critical concentration (hemi-micelle concentration) had high leaching resistance while ADBAC adsorbed into wood at above the critical micelle concentration (CMC) had low leaching resistance. The CMC decreased with addition of Mea and Cu-Mea. The anion, Cl- of ADBAC was only adsorbed at solution concentrations above the CMC and was easily leached out. The adsorption capacity of ADBAC into wood by cation exchange reaction did not achieve the cation exchange capacity (CEC) of wood. However, the total adsorption of ADBAC and Cu achieve the CEC of wood in the presence of copper amine, and ADBAC competes with copper to occupy the same sites in wood.
Myung Jae Lee, P Cooper
A comparison of the chemistry of alkaline copper and micronized copper treated wood
2010 - IRG/WP 10-30528
This paper discusses the chemistry of the reaction of alkaline copper and micronized copper with wood. The objective of this study is to examine the copper species produced in wood during the fixation reaction using electron paramagnetic resonance (EPR) spectroscopy. The initial experiments (phases 1 to 2) were designed to confirm the effect of time of treatment and solution concentration on the spectral parameters of copper in sawdust treated with copper sulphate solutions. The relative ease of distinguishing the copper produced from alkaline copper treatments with those produced during treatment of aqueous copper solutions was the focus of phase 3 while phase 4 examined the chemistry of sawdust treated with aqueous suspensions of copper carbonate. In the final phase, the focus was on determining whether a soluble copper species could be identified in wood treated with micronized copper preservatives. The spectra were compared to those of sawdust treated with aqueous suspensions of basic copper carbonate. The results of the study clearly show that soluble copper is produced relatively rapidly in wood treated with aqueous suspensions of basic copper carbonate and that this copper reacts with wood to produce similar copper complexes to that formed between wood and copper sulphate. These copper complexes resist leaching. This would support the premise that soluble copper formed by the reaction between basic copper carbonate and wood, can migrate into the wood cell wall in a manner similar to other soluble copper chemicals, and bind to wood cell components. Further research is in progress to further identify the chemistry of these reactions.
Wei Xue, P Kennepohl, J N R Ruddick
Evaluation of ACQ-D treated Chinese fir and Mongolian Scots pine with different post-treatments after 20 months of exposure
2010 - IRG/WP 10-30530
The performance of alkaline copper quat-type D (ACQ-D) treated Chinese fir (Cunninghamia lanceolata Hook.) and Mongolian Scots pine (Pinus sylvestris Linn. var. mongolica Litv.) stakes after 20 months exposure in Chengdu and Guangzhou of southern China were evaluated according to AWPA standard E07-07. The ACQ-D treatments used two concentration levels (0.5 and 1.0%) and four different post-treatments (air drying for 1 month, conditioning at 70°C, 80% R.H. for 24h, oven drying at 110°C for 24h, boiling in water for 15h), respectively. The field test results showed that the natural durability of Chinese fir is a little better than Mongolian Scots pine but the untreated sapwood stakes of both wood species were mostly destroyed after 20 months exposure. After ACQ-D treatment, the sapwood of both wood species showed much better biological performance. Among the four post-treatments, the oven drying method (OD) rated the worst by showing slight reduction in biological performance and the most obvious reduction in compression strength after exposure, while the other three post-treatments performed similarly. It suggested that both post-treatments of HC (conditioning in humidity chamber) and HW (hot water bath) could be good selections for accelerating copper fixation in ACQ-D treated wood. And also, Chinese fir from plantation forests could be a potential wood species for preservation.
Lili Yu, Jinzhen Cao, Wei Gao, Haitao Su
Distribution and availability of preservative components in ACQ treated wood - effects of coatings and weathering
2010 - IRG/WP 10-30537
Copper and quaternary ammonium compound (quat) distributions across lumber (gradients) and availability, as measured by amount removed by intensive leaching of wood flour, were measured in ACQ treated southern pine lumber. Samples were evaluated just after treatment and stabilization, or after 3 years of laboratory storage, or after 3 years of natural weathering exposure. The objective was to investigate how the distributions of copper, quat and monoethanolamine (MEA) changed under different exposure conditions to try to explain the long terms effects of semi-transparent wood coatings to reduce leaching, even after partial failure of the coatings. In unweathered lumber, there was a slight copper gradient from the surface to the interior of the lumber and a steeper quat gradient. Analysis of specimens after 3 years of weathering exposure confirmed the effectiveness of the coatings to reduce copper and quat leaching and showed that quat leaching from uncoated samples was substantial. There was little effect of aging indoors on availability of ACQ components. However, the availability of copper was significantly reduced after 3 years of natural exposure, even after accounting for the copper that leached during weathering. It was observed that the MEA availability was greatly reduced, presumably by preferential leaching compared to copper and quat during weathering. This appears to have reduced the amount of soluble/available copper resulting in lower long term copper leaching, especially in coated samples that were protected from high copper losses by the effect of the coating. The reduced quat leaching from coated samples is attributed to the long term effectiveness of the coatings in the earlywood portions of the samples.
T Ung, M Nejad, P Cooper