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Potential toxicants for controlling soft rot in preservative treated hardwoods. Part 4: Evaluation of combined diffusion and toxicity
1979 - IRG/WP 2129
A large number of inorganic and organic preservatives were evaluated as potential soft rot control chemicals, by their degree of inhibition of fungal growth after allowing them to diffuse through a 6 mm thick wood slab. The tests were inoculated with wood powder from soft-rotted CCA treated poles. Pentachlorophenol was unable to diffuse quickly through the wood slab, although formulations with hexylene glycol showed some promise. Hydroxyisoxazole gave good results as did a number of other organic materials including "Busan 30", "Busan 52", "Permapruf T", sodium oxinate, sodium trichlorophenate, "Gloquat C", „Hyamine 1622", butyl icinol, and the commercial bandage materials "Osmoplast" and "Wolman pole bandage". Of the inorganic materials tested, good results were obtained with "Basilit BFB", with other Cu-F-B formulations including "Blue 7", and with fluoroborate and fluorosilicate preparations in general. Arsenates also showed some promise.
E W B Da Costa, O Collett

Effects of the addition of polyethylene glycol to the CCA-C preservative treatment
1985 - IRG/WP 3337
A modification of the CCA-C wood preservative system for utility poles has been investigated to see if spur penetration into the poles is assisted during climbing. Addition of polyethylene glycol to the CCA system has been shown to accomplish this purpose. This paper addresses the effects of the addition of polyethylene glycol to other physical properties germane to utility poles.
W P Trumble, E E Messina

A chemical and mycological evaluation of fused borate rods and a borate/glycol solution for remedial treatment of window joinery
1983 - IRG/WP 3225
The possibility of using fused borate rods (Impel Borpatron) and a borate/glycol solution (Boracol-40) for depot impregnation of window joinery has been examined in a co-operative project between The Swedish Forest Products Research Laboratory, The Swedish University of Agricultural Sciences and Prolignum AB. The fused Impel rod is a glassy rod composed of disodium octaborate which readily dissolves and is distributed as bore acid when introduced into moist timber. Boracol-40 is a liquid containing disodium octaborate dissolved in glycol which has an ability to disperse in timber with a moisture content below 25%. The study involved treatment of a large number of windows in service as well as chemical and biological laboratory tests on the distribution and protective effect of the preservatives. In the field study about 100 windows, selected at random in various buildings in the Stockholm and Gothenburg areas were treated in-situ.
M-L Edlund, B Henningsson, A Käärik, P-E Dickèr

Remedial ground-line treatment of CCA poles in service. Results of chemical and microbiological analyses 6 months after treatment
1986 - IRG/WP 3388
CCA-treated poles in service with incipient internal soft rot were remedially treated by inserting borate rods, brushing with a boron/glycol solution and injecting boric acid paste, copper/creosote paste or a commercial product (DFCK paste). The spread of active chemicals in the treated zone as well as the change in microflora have been studied with time. After six months chemicals had spread to most parts of the pole in the ground-line zone and the microflora had been changed - in some cases drastically. The test is still in progress. Chemical and microbiological analyses after 12, 28 and 60 months will be published at a later date.
B Henningsson, H Friis-Hansen, A Käärik, M-L Edlund

The effect of glycol additives on diffusion of boron through Douglas-fir
2000 - IRG/WP 00-30235
Boron is highly effective against a variety of fungi and insects and is able to diffuse with moisture through wood. Diffusion decreases sharply at lower moisture contents, a characteristic that limits the potential use of this material as a remedial treatment for arresting internal decay. One approach to improvi ng boron diffusion is the simultaneous addition of glycol, which is presumed to enhance boron diffusion. In this study, the potential effects of glycol addition were explored by adding glycol plus boron (Boracol 20®, Boracol 40® or BoraCare®) or Timbor® and fused boron (Impel rods®) to produce a desired boric acid equivalent in each pole. Boron movement was assessed by periodically removing increment cores for chemical analysis. All of the supplements improved the diffusion of boron through Douglas-fir wood. Timbor®, which does not contain glycol, resulted in the most even distribution of boron throughout the poles while Boracol 40® seems to have increased boron diffusion to the point of loss from the poles.
C M Freitag, R Rhatigan, J J Morrell

Prevention of Termite Tubing Over Non-Wood Construction Materials Using Glycol Borate
2004 - IRG/WP 04-30358
Glycol borates have been demonstrated to prevent termite tubing and attack of wood materials and are extensively used as termite preventative applications in new construction in the USA. This study evaluated the ability of such systems to prevent Formosan subterranean termite tubing over non-wood materials. Concrete was selected as a common inert construction material and tests were carried out following topical treatment of the concrete with a commercially available glycol borate. It was found that a glycol borate treatment on concrete restricted the ability of termites to construct tubes. Exploratory tubes were less than 20 cm and the treatment caused near complete termite mortality. The results suggest that glycol borates offer a novel approach to protect cellulosic materials within structures not built from wood.
W R Smith, J D Lloyd

Oral toxicity of TIM-BOR®, Bora-Careä, boric acid and ethylene glycol against the formosan subterrean termite and easter subterrean termite
1993 - IRG/WP 93-10045
Oral toxicities (LD50) of boric acid, TIM-BOR® (disodium octaborate tetrahydrate: DOT) and BORA-CAREä (40% DOT in ethylene glycol) and ethylene glycol (ca. 80% monoethylene and ca. 20% polyethylene glycol) were estimated. Oral toxicities of BORA-CAREä were significantly higher (LD50: 256.2 µg/g DOT and 304.9 mg/g BAE) than TIM-BOR® alone (LD50: 408.2 µg/g DOT and 485.7 µg/g BAE); indicating a potential synergism of DOT by ethylene glycol in BORA-CAREä.
M Tokoro, N-Y Su

Boracol 40 - A potential remedial and preservative treatment for lyctids
1983 - IRG/WP 1192
The paper reports on a preliminary assessment of the efficacy of a diffusion formulation, Boracol 40, when applied as a brush treatment: to the surface of Eucalyptus obliqua against the powder-post borer Lyctus brunneus. After a five month bioassay, Boracol 40 has severely retarded the progress of active infestations of Lyctus brunneus and has been 100 per cent effective as a preventative treatment
J W Creffield, H Greaves, C D Howick

Time-of-Flight Secondary Ion Mass Spectrometry Analysis of Polyethylene Glycol Penetration into Wood Cell Walls
2006 - IRG/WP 06-20328
Penetration of high molecular weight polyethylene glycol (PEG) into wood cell walls was investigated in red pine. PEG of different molecular weights (1000, 8000 and 20000) was labelled by bromination and treated samples were analyzed on Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) in dynamic mode. Both negative and positive spectra of the samples were collected in high spatial (bunched), high spectral (burst), and an intermediate (burst alignment) resolution mode. Spectral and image data were statistically analysed by principal component analysis (PCA). Negative spectra distinguished untreated from treated samples, showing Br allocation in cell walls of all treated samples. Positive spectra did not provide differentiation between PEG and wood components. Penetration of PEG of all molecular weights into cell walls was confirmed even in case of treatments with PEG 20000.
D Jeremic, P Cooper, P Brodersen

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

Properties of strand board bonded with ammonium pentaborate (APB) modified phenol formaldehyde resin
2009 - IRG/WP 09-40455
Ammonium pentaborate (APB) is combined with phenol formaldehyde (PF) resin in this study to develop a high-performance wood-based composite. The effect of APB and its combination with polyethylene glycol (PEG) on the physical, mechanical properties as well as formaldehyde emission of strand board were tested and compared with disodium octaborate tetrahydrateand (DOT) and zinc borate (ZB). The results showed that APB has negative effect on the mechanical properties of the strand board, but the distribution of APB only on the surface in the 3-layer strand board can reduce this negative effect significantly. Except only marginal increase on the thickness swelling, PEG displays a positive effect on internal bond strength, modulus of rupture (MOR), and modulus of elasticity (MOE). As expected, APB showed decreasing effect on the formaldehyde emission.
Wei Gao, Jinzhen Cao

Hygroscopicity of wood after polyethylene glycol (PEG) impregnation and/or heat treatment
2013 - IRG/WP 13-40623
The hygroscopicity of wood after polyethylene glycol (PEG) impregnation and/or heat treatment was investigated by testing the water uptake, equilibrium moisture content (EMC) at various relative humidity levels, and contact angle of the poplar wood surface. The results showed that: (1) At the first moment, the heat treatment at temperatures lower than 160 ℃ did not reduce the water uptake because of the lowered wettability of wood after those treatments. Afterwards, all the heat treatments showed positive effect on reducing the water uptake until they reached the same maximum after 48 d in this study. (2) PEG increased the water uptake at beginning but significantly decreased the maximum water uptake, and the PEG-heat treated showed additive effect by showing further lower maximum water uptake. (3) The molecular weight of PEG showed slight influence on both water uptake and moisture adsorption. (4) The heat treatment at temperatures below 160 ℃ showed little influence on equilibrium moisture content (EMC), but significantly decreased the EMC above 160 ℃. The combination of PEG-heat treatment produced inconsistent results at different relative humidity levels. After PEG 1000 impregnation, the EMCs were a little higher than those without PEG for both unheated and heat treated samples at high relative humidity conditions (75%). However, at low relative humidity conditions (11, 33, 57%), the EMCs of PEG treated wood are all lower than those without PEG impregnation. The reason needs to be further discussed.
Weiyue Xu Yuan Zhu, Jinzhen Cao

Borate Redistribution in Glulam in an Above Ground Field Test
2014 - IRG/WP 14-30652
Researchers have refocused on the use of boratesin the wood protection industry in the last two decades due to their broad spectrum effectiveness against fungi and insects, and favourable environmental characteristics. This study was designed to determine borate distribution in a limited number of samples from a large field test of composites protected by a combination of coating and borate treatment by two processes.The intended application of these products was exterior components of buildings with considerable protection by design, but the test method was designed to be a much more severe exposure. A variety of structural composites had been machined into ɣ-joint test samples, then borate-treated by two methods: a surface-applied penetrating process, and a dip treatment with borate/glycol plus insertion of copper/borate rods.After application of the coating the test samples had been installed in a long-term above-ground outdoor weathering trial at FPInnovations’ Maple Ridge, British Columbia test site. After seven years of exposure, selected glulam beams of black spruce, white spruce, and Douglas-fir samples were destructively sampled and analyzed for borate retention and penetration, with results compared to unexposed material.Results showed that borateshad migrated from the surface of exposed samples to inside the wood, as deep as 50 mm, and in many samples were present in concentrations that would be sufficient to prevent fungal decay.
P I Morris, A Temiz, J Ingram

Fabrication and characterization of MicroPCMs filled wood-plastic composites: Effects of polyethylene glycol on melamine–formaldehyde shell material
2016 - IRG/WP 16-40728
Microencapsulated phase change materials (MicroPCMs) containing dodecanol were fabricated using melamine-formaldehyde (MF) or polyethylene glycol 200 modified melamine-formaldehyde (PMF) resin as the shell materials by in situ polymerization. Wood flour/high-density polyethylene (WF/HDPE) composites with MF shell MicroPCMs (MF-MicroPCMs) or PMF shell MicroPCMs (PMF-MicroPCMs) were prepared, respectively. The synthesized MicroPCMs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Nano indentor, differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. Thermal energy storage abilities, physical and mechanical properties of the composites were investigated. The results showed that: (1) MicroPCMs were successfully prepared. The thermal and mechanical properties of MicroPCMs were improved by using modified PMF resin as shell material; (2) PMF-MicroPCMs imparted WPCs were potentials as thermal energy storage materials for temperature regulating applications, due to their appropriate phase change temperature (27.2, 11.3 oC) and outstanding thermal enthalpy (118.9, 111.5 J/g); (3) the incorporation of MicroPCMs had a negative effect on flexural and tensile properties of WPCs but favored to impact strength and surface hardness. All the mechanical strength values were qualified for the requirements of WPCs decorative boards.
Xi Guo, Jinzhen Cao

Wood Protection Using Nano Metal Oxides in Propylene Glycol
2022 - IRG/WP 22-30760
Metals and metal oxides are known to have properties that can protect wood from degradation. Nanoparticles, due to its unique physical and chemical properties can enhance the protection to a much greater extent. Major constraints in dealing with nanoparticle dispersion can only be resolved by identifying a proper dispersive medium. Studies were carried out by preparing nanodispersion of four metal oxides (ZnO, CuO, CeO2 and TiO2) in propylene glycol using ultrasonication without addition of any surfactant or dispersant. The process yielded stable dispersions without agglomeration or settling of nanoparticles and can be stored for longer durations. CuO dispersion showed less stability though complete settling of CuO nanoparticles was not observed. Antifungal assay as plate test show that 0.01 to 0.05% of nanoparticle dispersions can prevent white-rot and brown-rot fungal growth. Fungal resistance tests using nanodispersion treated wood specimens shows that nano-ZnO dispersion in propylene glycol inhibited decay more effectively than commercially available ZnO aqueous dispersion. CuO was more efficient in preventing decay than ZnO dispersion of same concentration. Nanodispersion provided termite resistance and 5% CuO treated specimens prolonged service life of treated wood specimens to more than one year. UV stability of wood surfaces coated with nanodispersion of ZnO, CeO2 and TiO2 was evaluated under laboratory conditions in an accelerated weathering tester. Increase in concentration of nanoparticle from 1% to 2.5% significantly enhanced UV resistance. However, increase in nanoparticle concentration reduced transparency particularly in ZnO and TiO2. Results indicate that propylene glycol can be considered as a viable dispersant to prepare nanoparticle dispersions, as it provides stability to the dispersion without affecting the photo-screening effect of nano metal oxides. The results of the study will help in developing a nano-based wood preservative formulation with increased antifungal and anti-termite properties.
S Nair, G B Nagarajappa, K K Pandey

Preservative Treatment of CLT: An Example at Shimojishima Airport
2019 - IRG/WP 19-30748
Cross laminated timber (CLT) is a relatively new construction method that allows multi-storey construction using solid wood instead of concrete or steel. It is a method favoured by progressive architects and recognized for its much lower environmental footprint. Wood is an excellent construction material and is a long-term carbon sink that also performs well in the event of earthquakes and fire. Obviously being made of a natural organic material, durability performance against mold and wood destroying organisms is a concern. Even if it were possible to permanently keep the wood dry to prevent wood rotting basidiomycete fungi, some pests are able to attack wood that is wetted temporarily (e.g. mold fungi) or even relatively dry wood (e.g. subterranean termites, wood destroying beetles, dry wood termites and carpenter ants. In most parts of the world there is an active remedial treatment market dealing with decay in structures that were also supposed to be kept dry. In the USA damage caused by decay fungi is thought to be even greater that that caused by subterranean termites (Smith and Whitman 2007). The relatively modern use of indoor plumbing and air conditioning has increased interior moisture issues due to water leaks and condensation. In single family residential construction, when problems occur it is relatively easy to carry out remedial treatment of infested structural wood and wood replacement. Even whole structural subfloors sometimes need replacement due to decay caused by high humidity in conjunction with air conditioning. However, it is NOT easy in multi-storey mass timber construction. For this reason, a global representation of wood scientists has discussed this issue and even signed an open letter on the need to address durability of mass timber construction (Taylor et al. 2016). Countries with subterranean termite problems typically have good standards that address them. Soil poisons, primary barrier wood treatments (to a certain height of the structure) and physical barriers, are well entrenched as control methods (Lloyd et al., 2015). However, none of these methods control the other wood destroying organisms. Wood treatment applied to the bottom ~1 meter of a structure was developed originally in Japan and, with glycol borates, is now the leading commercially applied termite preventive treatment in the USA (to meet the US Department of Housing and Urban Development, State and building code requirements). This can be extended to whole house wood destroying organism control (Lloyd et al., 2015). Possible approaches to address durability include the use of naturally durable wood or pressure treatment of wood with appropriate preservatives. A topical treatment (to avoid significantly re-wetting otherwise dry wood) with a diffusible preservative (to move in the event of enough moisture to support decay) and a moldicide may also be adequate. Such treatments could be carried out by spray, dip or double vacuum application and do not typically cause dimension changes (Jermer & Lloyd, 2000). Borates (especially glycol borates for dry wood e.g. Turner, (2008)) have the advantage of being effective against both decay fungi and insects at low retentions (Lloyd, 1997) and are even bait toxicants against subterranean termites at low retention (e.g. Jones, (1991). Such approaches have been successfully used in residential construction such as under the old German Standard DIN 68-800 where lumber was dipped in a 10% disodium octaborate tetrahydrate solution. The use of an inorganic salt as the active ingredient is also good in topical applications where organic systems can be destroyed by UV light during construction (Lloyd et al., 1998). Even non wood destroying insects such as psocids and cockroaches can be controlled via the use of borate treated wood (Lloyd et al., 2003). Borates have low acute mammalian toxicity are globally available from a number of suppliers. To enhance moldicidal performance there are a number of good active ingredients including quaternary ammonium compounds, carbamates, chlorothalonil, azoles and isothiazolinones. An example of such a treatment includes the Arch/Lonza Frame Guard system commercialized in the USA (Lloyd, 2015). Using topical treatments also has the added advantage of being able to change formulations relatively easily (for example you could use different borate concentrations for geographies with and without subterranean termites) and to ensure that all of the construction components are treated (the mass timber itself but also framing and plywood and many other SKUs that typically go into a building. A 40% disodium octaborate tetrahydrate in glycol formulation (commercially available as Boracare from Nisus Corporation) has performed very well in 10- and 15-year field tests in Mississippi (Williams & Amburgey 2003) and Florida (Barnes et al., 2014) against subterranean termites, in preventive and remedial drywood termite tests (Austin & Gold, 2006; Lewis 2012), and in decay tests such as AWPA E 10 (Amburgey et al., 2004). Formal testing was also carried out in Japan as part of the JWPA approval procedure. In addition, a field test was carried out specifically for the Shimojishima Airport project. A separate series of diffusional penetration and rain exposure leaching tests that we carried out in Japan were also useful. Mitsubishi Estate Co., Ltd. organized the construction which was designed by Nikken Sekkei Ltd. architectural office and built by local contractors for Mitsubishi Estate Co. Ltd. The commercial operations of the Airport are carried out by Shimojishima Airport Management Co. Ltd. Topical treatment was carried out using a 40 % DOT glycol borate diluted at a 1 to 1 volume dilution in water (Boracare to equal a 23 % DOT solution concentration). 0.8 % diecyl dimethyl ammonium chloiride (1% as Moldcare available commercially from Nisus Corporation) was added as a surface moldicide. The diluted material was applied with roller coating at Yamasa Mokuzai Co. Ltd., the CLT manufacturer. An application of 300ml m2 was used in compliance with JWPA requirements to treat 6,000 m3 of CLT. This is a higher concentration and higher application rate than required by US EPA registered label against all non-subterranean termite organisms but was chosen to help drive diffusion over time, to give protection against subterranean termites, to enhance spread of flame performance, and to supply some reservoir to compensate for dilution due to diffusion into the wood. All testing and treatment results went well, and the construction is now complete. The inaugural direct flight from Narita to Shimojishima was March 30th 2019 and many more flights will be able to land in an airport that is effectively storing carbon, and will remain free of drywood termites and other wood destroying organisms for the decades to come. If mass timber and especially CLT is to gain the position it deserves in future construction, it is essential that long term durability is addressed. This project has shown that is relatively easy and cost effective to do so.
J Lloyd, N Yamashita, A Taylor