Borate Wood Preservatives: The Current ... - American Chemical Society

Chapter 26

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Borate Wood Preservatives: The Current Landscape M a r k J. Manning U.S. Borax, Inc., 26877 Tourney Road, Valencia, C A 91355

Borates have been used as wood preservatives for over 70 years - providing excellent control of wood destroying organisms such as decay fungi and termites. Because of their water soluble nature, the use of borates have been limited to applications where the wood is used in protected, aboveground applications such as lumber for residential construction. In recent years, less soluble borates such as Zinc Borate (2ΖnΟ 3Β O 3.5Η O) have been used as preservatives to treat wood- and wood-plastic composites which are used in less protected applications such as exterior siding and aboveground decking. This paper will also highlight the current situation with the use of Zinc Borate as a preservative treatment for wood composites, providing protection for these commodities when used in exterior above-ground applications. ·

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© 2008 American Chemical Society In Development of Commercial Wood Preservatives; Schultz, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.

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Introduction Boron-containing wood preservatives are all derived from naturally occurring borate minerals. The mineral borax, Na2B4O7*10H2O is the most significant commercial source of B 0 ; there are major deposits in both the United States and Turkey. Probably the most commonly used form of boron for wood preservation is the compound Disodium Octaborate Tetrahydrate (DOT, Na2B8013'4H20), sold under the trademark Tim-bor® Industrial (U.S. Borax Inc.); it exhibits high water solubility and has a near neutral pH. Borates in general, and D O T in particular, possess a number of properties that help to make them unique wood preservatives:


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Inorganic salts (nonvolatile) Low mammalian toxicity High toxicity to insects and fungi No tolerance by wood-destroying insects Odorless Near neutral pH Noncorrosive Colorless Strength properties similar to untreated wood Compatible with colorants if visual marking is desired

When used correctly they can give effective long-term treatment that is also economical and environmentally sound. Borates possess a very favorable ecotox profile (7). They occur naturally in seawater, fresh water, rocks, soils, and all plants. The earth consists of trace amounts of more than 200 minerals that contain boron. In trace amounts, they are essential micronutrients for plants and believed to be nutritionally important for humans. Like many trace elements, boron is both essential at low concentrations and toxic at high concentration - allowing the borates to be effective preservatives against wood destroying organisms. Borates are members of a class of waterborne chemical preservatives which are diffusible in wood. Using the available moisture in unseasoned wood, the chemical redistributes itself after the treatment - diffusing from areas of high concentration (of chemical) to areas of lower concentration. The water-soluble chemical equilibrates in such a way as to reduce the concentration gradient. This capability for the chemical to diffuse after treatment makes it possible to completely penetrate unseasoned wood, thereby allowing effective treatment of refractory species. The subject of diffusible preservatives has been reviewed in the context of these systems offering highly effective and flexible options, for

In Development of Commercial Wood Preservatives; Schultz, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.


442 both standalone preservatives and as components in more specialized formulations (2). Boron compounds in current use as wood preservatives are susceptible to leaching under certain conditions, as they are not chemically fixed within the wood. A common misconception is that small amounts of moisture will readily leach boron out of the wood - this is simply not the case. In order for leaching to occur there needs to be a situation where liquid water enters the wood at one point and then leaves at another point, also as liquid water. This topic has been reviewed (3). Because of this potential for depletion when exposed to significant moisture, borates are normally recommended for general building use in a protected environment and are not recommended for use in ground contact. This particular end-use is delineated in the original borate treating standard that was published by the American Wood-Preservers' Association: A W P A Standard C31-02 (4), "Lumber Used Out of Contact with the Ground and Continuously Protected from Liquid Water - Treatment by Pressure Processes". More recently, the A W P A has moved to a Use Category System (UCS), utilizing a framework whereby the intended application (end-use) of the treated wood product is used to specify the appropriate standard and preservative retention. Borates are listed in A W P A Use Category UC1 and UC2. UC1 is for wood and wood based materials used in interior construction not in contact with the ground or foundations (e.g., interior furniture and millwork). U C 2 is for wood and wood based materials used for interior construction that are not in contact with ground, but may be subject to dampness - products that are continuously protected from the weather but may be exposed to occasional sources of moisture (e.g., interior framing and sill plates). A number of recent trends are driving the development of wood preservation activity over the last decade. Among those highlighted have been: changing building practices (wood losing market share to termite resistant building materials such as steel and concrete), increased need for value added production and the emerging area of preservative treatment of wood composites (5). These issues all have relevance to the current development of boron based wood preservatives in North America and will be discussed in the following section. There have been several reviews published on the use of these preservatives (1,6,7) and a review of efficacy data against decay fungi and termites has also been compiled (5).

Recent Developments in North America As described earlier, borates are referenced in the A W P A Book of Standards. The Standard for Waterborne Preservatives (Standard P5) lists



443 Inorganic Boron (abbreviated as S B X ) and the acceptable boron preservatives: DOT, Sodium Tetraborate, Sodium Pentaborate, Boric Acid, and FR-1 (a fire retardant system containing boron). The wood species listed in A W P A Standard C31-02 as well as UC1 and UC2 are: Southern Pine, Hem-fir (Western Hemlock and Amabilis fir), Ponderosa Pine, Red Pine, Spruce-Pine-fir (SPF), and Coastal Douglas fir. The listing of Coastal Douglas-fir includes a requirement for incising, while the listing for Hem-fir and SPF does not include an incising requirement. The absence of an incising requirement for these refractory species is due to the diffusible nature of the borate preservative. Borates are also listed for the same species in the Canadian wood preservation standard C S A 080.34 (Canadian Standards Association). The desire to protect buildings from wood destroying organisms (WDO) such as decay fungi and termites is well established and evident in mandates by building codes in many regions of the United States, as well as in standards required by home mortgage lenders. The predominant method of protecting homes requires establishing a barrier against subterranean termites by treating the soil under and around homes prior to construction and treating in and around existing homes when termites are detected. Additionally, treated wood is used for selected building elements such as sill plates. This approach provides some relief, but even perfect barriers don't protect structures against aerial colonyforming termites such as Formosan subterranean (Coptotermes(FST) formosanus Shiraki) and drywood termites, carpenter ants, or from wood decay. Additionally, chemical barriers are often disturbed in the construction process or by simple homeowner activities such as landscaping, and degrade over time! Historically, organochlorine pesticides such as chlordane, aldrin, and heptachlor were used to place a chemical barrier at the soil level. These materials were long lasting (30 to 50 year life) and the vapor pressure from these materials would "fill in" any missed or disturbed areas to provide a continuous layer of protection. These properties, while functionally desirable in a termiticide, were environmentally unacceptable. As a result, chlordane and other organochlorine pesticides were removed from the market in the late-1980s. The current termiticides are less persistent (effective working lives of about 5 years) and much less forgiving of applicator error and disturbances. A recently described approach for mitigating damage caused by W D O is the Six " S " strategy: Suppression, Site management, Soil barriers, Slab and foundation details, Structural protection, Surveillance, and remediation (9). Structural protection is the most straightforward and important single operation among the six. It involves two basic elements: managing moisture within the building assemblies and choosing materials that are protected against W D O . Wood that has been pressure treated with borates has been successfully used for the latter objective in various parts of the world where termites, decay and other wood-destroying organisms pose significant problems. In New Zealand, for



444 example, the use of borate-treated lumber and plywood for the entire structure has been standard practice for more than 50 years. Borate-treated wood has shown excellent performance as a building material in the wet environment encountered in New Zealand, effectively making obsolete the need for remedial treatment and repair for homes built with this material (J). Hawaii is known to have the highest Formosan subterranean termite pressure in the United States. The use of treated wood for structural systems has been a requirement of the building codes there since the early 1980s. When borate-treated wood was first introduced into the Hawaiian market in 1992, it quickly became the most widely used structural material for building homes. Since its introduction, borate-treated lumber and plywood (sold locally as Hibor®, registered trademark of STN Holdings) have become the market leader in treated framing - providing a safe, effective and economical option for the residential home builder. This Hawaiian model has recently been transplanted to the Southeastern U.S. where it is currently being used for protecting homes (both single and multi-family) from damage caused by decay fungi and wooddestroying insects such as the Formosan subterranean termite. Borate-treated wood has performed extremely well - both in rigorous field tests and as structural systems for homes built in these very challenging environments. These successful efforts in New Zealand, Hawaii, and the Southeastern U.S. has been combined in a design concept called Borate Treated Structural System (BTSS) - wherein the structural elements of a home are industrially pre-treated with borate wood preservatives. One of the most significant uses of borates in North America is as a preservative treatment for sill plate material in residential construction (UC2 application described above). Extensive data was presented to the A W P A supporting the use of borate-treated lumber for this application, showing that there is no loss of efficacy when used as sill plate material. This has led to borate-treated lumber being listed in the most recent edition of the International Residential Code - the most widely accepted building code in North America for residential construction (70). Additional support for the use of borates as a preservative treatment for sill plate is provided by research being carried out by the Wood Research Institute at Kyoto University, Forintek Canada, and the University of Hawaii (77). Field tests were established to evaluate borate-treated Hem-fir lumber against the Formosan subterranean termite in a covered, above-ground exposure that was specifically designed to simulate the use of dodai (sill plate) material in Japanese residential construction (12-14). This test is still on-going with end-matched samples exposed to active FST colonies: one piece evaluated in Hawaii while the 'sister' piece is exposed to an FST colony in Japan. It is tentatively planned to carry out the test for a total of 10 years at each location. After six years in Hawaii and seven years in Japan, the borate-treated samples are exhibiting


445 performance equivalent to that of the 0.25 pcf C C A (Copper Chrome Arsenate) which is being evaluated as a comparison control in the same test. The six-year results from the test in Hawaii are displayed in Figure 1. Results from these tests were instrumental in helping to establish an A W P A borate retention for exposure to the FST: 0.28 pcf B 0 - the same retention approved by the Honolulu Building Department for use as a preservative treatment in Hawaii. This test is very severe in that the test units are located directly on top of active FST colonies. It should also be noted that because of the warmer temperatures, the termite pressure in Hawaii is thought to be ~3x as severe as that in Japan, so that a 6 year exposure in Hawaii is considered to be comparable to ca. 18 years exposure at the Japanese test site in Kagoshima Prefecture (Island of Kyushu) (13). Additional tests are ongoing which are evaluating a variety of wood species (Douglas-fir, Southern Yellow Pine, Spruce-Pine-Fir, Hem-fir, and Ponderosa Pine) treated to different borate retentions. In this test, the wood samples have been assembled into small 'house-like' structures (~ 1 m in size) with sloped, plastic roofs, such that the test specimens are placed in protected, above-ground exposures. This equates to A W P A Use Category 2, which is the exposure for framing lumber used in residential construction. In this test (and the extended duration Hem-fir Dodai test previously discussed), it should be noted that the termite hazard is exceptionally severe in that untreated feeder stakes are driven into the ground with the upper surface placed in contact with the borate-treated sample; this is done in an ongoing effort to bring the FST up into the test unit and in contact with the treated specimens. In typical residential construction the exact opposite occurs - the builder and subsequent homeowner do everything possible to inhibit future termite pressure (eg., soil treatment, minimal use of wood in ground contact, regular inspections by pest control operators, etc.) (9). In addition to termite pressure, wooden sill plates are also exposed to a decay hazard. In the extended sill plate exposures described above, there has been no evidence for decay in any of the borate-treated samples after 6 years in Hawaii and 7 years in Japan. This excellent performance of borates against decay fungi is highlighted in some L-Joint data developed by Forintek Canada (15). Hem-fir lumber was dip-treated with Disodium Octaborate Tetrahydrate (Tim-bor Industrial) to an average cross-sectional retention of 0.25% Boric Acid Equivalent (BAE) w/w and was subjected to a conventional L-Joint study (used to evaluate preservatives for exterior joinery; the treated wood is protected with a three coat paint system and is exposed directly to the elements, with no protective overhang as is typically seen in normal construction). A set of 30 treated samples was installed along with a set of 30 untreated samples. The results for average visual ratings after 12 years exposure are displayed in Figure 2. The untreated samples had an average rating of 1.5 (23 of the 30 untreated samples had failed) while the treated samples had an average rating of 9.3.


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Average Rating

Figure 1. University of Hawaii / Forintek Canada / Wood Research Institute Kyoto University. Six year data from Hem-fir Dodai samples exposed to the FST in a covered, above-ground test. Average visual ratings are on a 0 to 10 scale; rating of 10 indicates no attack while a rating of 0 indicates that the sample has been completely destroyed.



Figure 2. Average visual ratings for L-Joint samples exposed for 12 years in Vancouver, B.C. Average visual ratings are on a 0 to 10 scale; rating of 10 indicates no attack while a rating ofO indicates that the sample has been completely destroyed.



448 The samples were exposed in Vancouver, B.C. where the average annual rainfall is - 4 0 " (-1000 mm). After 5 years exposure (cumulative precipitation of -200" (-5000 mm)) a set of five treated samples were removed and chemical assays were carried out; these results showed minimal boron levels (0.02% B A E ) in the area of the joint with evidence for a 'reservoir effect' with boron being depleted in the area of the joint while being replenished from the ends. O f particular note here is the protection against decay being afforded by the extremely low levels of boron in the area of the joint. The boron is providing protection at retentions significantly below what is normally suggested as a toxic threshold - providing support that low levels of boron may inhibit spore germination. The excellent performance of the borate-treated samples after 12 years is even more noteworthy when one considers that the initial retention was approximately one-quarter of the non-Formosan A W P A Standard of 0.17 pcf B 0 . Structural protection for W D O involves two basic elements: 1) managing moisture within the building assemblies and 2) choosing materials that are protected against W D O . Sometimes, non-wood building materials are chosen solely because they are resistant to decay and insect attack, when wood products would otherwise be the material of choice. However, common building materials such as steel and concrete can increase the water loading in the building envelopes, providing a more favorable environment for wood destroying organisms. Water can condense on the steel frame members, creating problems of corrosion, decay and insects. Concrete is a porous material and allows moisture to migrate and accumulate on the cool side of the block wall, creating a condition for W D O to prosper. Wood that has been industrially pre-treated with borates has been successfully used for structural systems in various parts of the world where termites, decay, and other wood destroying organisms pose significant problems. This has resulted from the realization that it is far more cost effective and environmentally responsible to provide lasting, built-in protection to the very building components and systems that are susceptible to degradation than to provide remedial protection year after year. In the United States, it has been shown that many new homes are suffering damage from W D O . At a national level, it has been estimated by the Wood Protection Council of the National Institute of Building Sciences that the annual cost to replace wood severely damaged by decay and termites increased from $750 million in 1988 to over $2 billion in 1993 (76). The economic loss continues to grow with some estimates indicating that Florida and Louisiana each spend $1 billion per year to repair and treat damage by WDO. It is widely believed that current costs are significantly greater. The success in the use of borate wood preservatives for treating structural materials is due to its many performance attributes. Borates have a wellestablished record of performance against a broad spectrum of wood destroying 2

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449 organisms. Borates are cost effective and easy to use for the preservative treatment of solid sawn lumber, plywood, and wood composites such as oriented strand board (OSB). Lumber and plywood is pressure treated with waterborne borates such as DOT, whereas with OSB the borates are added to the wood composite during the manufacturing process. In treated wood, borates are colorless (although a dye is often added), non-volatile, and robust so they don't evaporate, degrade, or produce an odor during service; and are non-corrosive, requiring no special fasteners. The implication to builders and designers is that significant protection against termites and decay can be built into the structure without having to make drastic changes in design or to the construction process.

Preservative Treatment of Composites with Zinc Borate The species, size, and quality of standing timber available for harvest is changing world-wide and this is promoting the development and extended use of wood composites in applications which require resistance to wood destroying insects and decay fungi. Traditionally, solid wood products are pressure treated with solutions of preservative chemicals. However, the nature of a composite makes it possible to incorporate a preservative into the product during its manufacture. This decreases total production costs and yields a superior product in which the composite can achieve a constant loading of preservative throughout its thickness. Both D O T and Zinc Borate (ZB, 2ΖηΟ·3Β2θ 3.5Η2θ) are suitable for incorporation into wood composites, although Z B has been used almost exclusively for exterior composite products where there is a perceived risk of leaching. Zinc Borate is a white odorless powder (median particle size of 9 microns) and is typically mixed in the blender with the wood furnish, adhesive and wax. Z B is manufactured by U.S. Borax Inc. and sold under the trade name BorogarcF Z B (registered trademark of U.S. Borax Inc.). Z B exhibits low water solubility at room temperature (35% by 2010 (25). When WPCs were introduced in the early 1990s, the common perception was that the 'wood fiber was encapsulated' by the plastic resin, thereby minimizing the potential for moisture absorption and protecting it against W D O . In reality, wood particles near the surface of commercial WPC products may be subject to levels of water absorption that can initiate and support fungal decay (it is accepted that this water absorption takes place in the wood component and not in the plastic phase). Recently there have been reports which have examined the durability of these products in relation to artificial weathering and the impact on water absorption (27). This work has yielded data which shows that small samples (with high surface area to volume ratios) submerged in water can achieve the necessary % moisture content ( M C ) in the wood component to support decay fungal growth in less than 24 hours. Laboratory water absorption evaluations used by the W P C industry on -300 mm lengths of conventional sized, freshly extruded samples which have not been weathered exhibited % M C values for the wood component which were less than 10%, well below the minimum threshold of 25% M C necessary for the onset of fungal decay. This concept of the wood component being encapsulated by the plastic is supported by test methods that the W P C manufacturers utilize to evaluate moisture absorption. The A S T M D-1037 method utilizes a 24 hour water soak on large-sized specimens (12" long by 6" wide by product thickness) and is used by W P C manufacturers to generate water absorption values for their commercial products - typically yielding values of 1-2% weight gain. For a WPC material


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that is comprised of an approximate 50:50 wt. ratio of wood:plastic, a weight gain of 1-2% corresponds to a M C of 2-4% in the wood component (it is assumed that the plastic component does not absorb moisture). If the % M C for the wood component is maintained at this low level, there would be insufficient moisture to support biological growth such as wood decay fungi. Zabel and Morrell (28) have outlined the growth needs for woodinhabiting fungi: • • • • • •

Water (minimum of 25-30% M C ) Oxygen Favorable temperature range ( 15 - 45° C) Digestible substrate (wood) Favorable p H range (pH 3 - 6 ) Chemical growth factors (Nitrogen, vitamins)

As part of our work with these materials, commercial W P C samples were evaluated against decay fungi using the A W P A Soil Block test method (3). A l l of the samples were based on polyethylene/wood, with the wood content ranging from 50 to 70% of the product weight. Samples that were leached prior to exposure to the decay fungi exhibited weight losses ranging from 0.45% to 22.1% for the white rot organism Trametes versicolor and 0.23% to 7.99% for the brown rot organism Gloeophyllum trabeum. Unleached samples exhibited weight losses ranging from 0.20% to 18.1% for T. versicolor and 0.54% to 7.34% for G. trabeum. The higher weight losses in the T. versicolor tests were presumably due to the wood content in these samples being predominately hardwood. Samples with the highest weight loss had wood contents close to 50%; for samples with weight loss in excess of 20% (based on product weight), this yields a loss for the wood component of ca. 40%. The image in Figure 3 was taken by an optical microscope and shows the surface of a W P C sample prior to being exposed to the decay fungi in the laboratory soil block test. Figure 4 shows the surface of the same WPC sample after exposure to the decay fungi - in this case the degradation of the wood component is clearly evident with the appearance of void spaces where the decay fungi have metabolized the wood. Other researchers have evaluated biological attack on WPC materials using a scanning electron microscope (29). In all of the samples that exhibited weight losses, the degradation was most severe on the surface that was in direct contact with the decay organism at the start of the test. As part of the decay evaluation that was previously described, a series of extruded W P C samples (both commercial and toll produced) were treated with Z B at target retentions of 0.5, 1.0, or 2.0% Z B (w/w) during the manufacturing process and exposed in the A W P A laboratory soil block procedure. In all samples evaluated (both leached and unleached), the WPC materials treated with



Figure 3. Surface of untreated WPC sample (ΙΟΟχ magnification) before A WPA E10 Decay Evaluation.


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Figure 4. Surface of untreated WPC sample (at lOOx magnification) after A WPA Ε10 Decay Evaluation.


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Z B did not exhibit signs of fungal decay as evidenced by weight loss values that were all less than 1.1%. When compared with the earlier decay data on untreated W P C material, these results clearly demonstrate the significant improvement in protection against fungal decay afforded by the addition of low levels of Z B . In 2006, it is forecast that upwards of 35% of the WPC production in North America will be preservative treated with Zinc Borate.

Future Developments There are still research efforts underway with the aim of producing a leachresistant or "fixed" borate which could potentially expand the use of borates in the preservative treatment of solid wood. Many workers have been interested in this goal and some of the most interesting results to date have been achieved by the use of insoluble borates that are slowly solubilized to liberate boron in solution. Probably the best and most widely commercialized has been the use of the sparingly soluble zinc borate mentioned earlier. The low degree of water solubility exhibited by the zinc borate has allowed this preservative to pass currently utilized leaching tests and provide subsequent performance against decay fungi and wood destroying insects. The solid zinc borate slowly dissolves to yield low levels of zinc borate in the aqueous phase. This subsequently hydrolyzes to generate zinc hydroxide and boric acid. The zinc hydroxide precipitates in the wood while the low levels of boric acid can diffuse throughout the composite, providing protection where it is needed. However, the use of zinc borate as a slow-release diffusible preservative is currently only being carried out as a treatment for wood composites. The ability to incorporate the "leach resistant" preservative during the manufacture of the wood composites is an obvious advantage over trying to generate such a complex in situ. Such a strategy, (in situ deposition of low solubility boron compounds which are also effective preservatives) has proven to be a challenging goal for the preservative treatment of solid timber, although work continues in laboratories around the world. When the balance between leach resistance through insolubility and enhanced diffusion through limited dissolution are fully understood, ways to optimize such treatments are possible. Judging by the degree of research activity in the area of diffusible preservatives, rational preservative design represents an achievable goal. This update has touched on the wide range of technologies that can be used to treat wood with borates - from solid lumber to wood composites and, more recently, the emerging field of wood-plastic composites. Critical to the continued growth of boron-based wood preservatives will be their use in appropriate applications such as UC1, UC2, and more recently U C 3 A . B y their very nature, diffusible borate preservatives are more forgiving of variations in treatment regimes than many of the more conventional preservative types.


455 Coupled with the broad spectrum of biological efficacy, this flexibility puts boron preservatives in a very strong position for the future.

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Lloyd, J.D. 1997. International Status of Borate Preservative Systems. In: Proc. The Second International Conference on Wood Protection with Diffusible Preservatives and Pesticides. Forest Products Society. Madison, WI. pp. 45-54. Manning, M . J . , Lloyd, J.D. and M . W . Schoeman, 1997. The Future of Diffusible Preservative and Pesticide Systems. In: Proc. The Second International Conference on Wood Protection with Diffusible Preservatives and Pesticides. Forest Products Society. Madison, WI. pp. 157-168. Lloyd, J.D. 1995. Leaching of boron wood preservatives: a reappraisal. In: Proc. Annual Conv. British Wood Pres. and Damp Proofing Association. American Wood-Preservers' Association (AWPA). 2002. Standard C31-02. Lumber Used Out of Contact with the Ground and Continuously Protected from Liquid Water - Treatment by Pressure Processes. A W P A Book of Standards. A W P A , Granbury, Texas, pp. 187-189. Vinden, P. 1990. Treatment with Boron in the 1990's. In: Proceedings of the First International Conference on Wood Protection with Diffusible Preservatives. Forest Products Research Society. Madison, WI. pp. 22-25. Cockroft, R. and J.F. Levy. 1973 Bibliography on the Use of Boron Compounds in the Preservation of Wood. J. of the Inst. of Wood Sci. 6(3): 28-37. Barnes, H . M . , Amburgey, T.L., Williams, L . H . and J.J. Morrell. 1989. Borates as wood preserving compounds: The status of research in the United States. Doc. No. IRG/WP/3542. International Research Group on Wood Preservation, Stockholm, Sweden. Drysdale, J.A. 1994. Boron Treatments for the Preservation of Wood - A Review of Efficacy Data for Fungi and Termites. Document No. IRG/WP 94-30037. International Research Group on Wood Preservation, Stockholm, Sweden. Morris, P.I. 2000. Integrated Control of Subterranean Termites: the Six S Approach. In: Proc. of the American Wood-Preservers' Association, 96. pp. 93-106. International Residential Code for One- and Two-Family Dwellings, International Code Council, 2003. Grace, J.K., Byrne, Α., Morris, P.I. and K . Tsunoda. 2004. Six-year Report on the Performance of Borate-treated Lumber in an Above-ground Termite Field Test in Hawaii. Document No. IRG/WP 04-30343. International Group on Wood Preservation, Stockholm, Sweden.



456 12. Grace, J.K., Tsunoda, Κ., Byrne, T. and P.I. Morris. 1995. Field evaluation of borate-treated lumber under conditions of high termite hazard. In: Wood Preservation in the '90s and Beyond. Forest Products Society. Madison, WI. p. 240. 13. Tsunoda, K . , J. K . Grace, T. Byrne, and P. I. Morris. 2002, Mokuzai Gakkaishi 48: 107-114 (in Japanese). 14. Grace, J.K. 1997. Review of recent research on the use of borates for termite prevention. In: Proc. The Second International Conference on Wood Protection with Diffusible Preservatives and Pesticides. Forest Products Society. Madison, WI. pp. 85-92. 15. Morris, P.I. 2000. Ten year Performance of L-joints Made From Borate Diffusion Treated Wood. Document No. IRG/WP 00-30225. International Group on Wood Preservation, Stockholm, Sweden. 16. Wood Protection Council. 1993. National Institute of Building Sciences, "Wood protection guidelines - protecting wood from decay, fungi, and termites", November 1993. 17. Laks, P.E. and M.J. Manning. 1995. Preservation of wood composites with zinc borate. IRG/WP 95-30074. International Research Group on Wood Preservation, Stockholm, Sweden. 18. Laks, P.E. 1999. The Past, Present and Future of Preservative -Containing Composites. In: 33 International Particleboard/Composite Materials Symposium Proceedings. Wolcott, Tichy, Bender, Eds. Washington State University, Pullman, W A . pp. 151-158. 19. Manning, M . J . 2002. Wood Protection Processes for Engineered Wood Products. In: Enhancing the Durability of Lumber and Engineered Wood Products. Forest Products Society. Madison, WI. pp. 131-136. 20. Laks, P.E., D.L. Richter and G . M . Larkin. 2001. Preservative Systems for Wood Composites. In: Proc. 21 Annual Meeting of the Canadian Wood Preservation Association, pp. 177-187. 21. Silva, Α., C. Freitag, J.J. Morrell, and B . Gartner. 2001. Effect of Fungal Attack on Creep Behavior and Strength of Wood Plastic Composites. In: Proc. The Sixth International Conference on Woodfiber-Plastic Composites. Forest Products Society. Madison, WI. pp. 73-77. 22. Simonsen J., C. M. Freitag and J.J. Morrell. 2001. Effect of Wood-Plastic Ratio on the Performance of Borate Biocides Against Brown Rot Fungi. In: Proc. The Sixth International Conference on Woodfiber-Plastic Composites. Forest Products Society. Madison, WI. pp. 69-72. 23. Verhey, S.A., P.E. Laks and D . L . Richter. 2001. The Effect of Composition on the Decay Resistance of Model Woodfiber-Thermoplastic Composites. In: Proc. The Sixth International Conference on WoodfiberPlastic Composites. Forest Products Society. Madison, WI. pp. 79-86. 24. Manning, M.J. and F . M . Ascherl. 2003. Borates as Fungicides in WoodPlastic Composites. In: Proc. The Seventh International Conference on Woodfiber-Plastic Composites. Forest Products Society. Madison, WI. pp. 69-78. rd

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457 25. Morton, J. Current and Emerging Applications for Natural & Wood Fiber Composites. Paper presented at the 7 International Conference of Woodfiber-Plastic Composites, Madison, WI. May 19-20, 2003. 26. Pendleton, D.E., T.A. Hoffard, T. Adcock, B . Woodward, and M.P. Wolcott 2002. Durability of an Extruded HDPE/Wood Composite. Forest Prod. J., 52(6):21-27 27. Mankowski, M . E . , Ascherl, F . M . , and M.J. Manning. 2005. Durability of Wood Plastic Composites Relative to Natural Weathering and Preservative Treatment with Zinc Borate. IRG/WP 05-40316. International Research Group on Wood Protection, Stockholm, Sweden. 28. Zabell, R.A. and J.J. Morrell. 1992. Wood Microbiology: Decay and Its Prevention. Academic Press Inc. San Diego, C A . pp. 90-91. 29. Mankowski, M. and J.J. Morrell 2000 Patterns of Fungal Attackin WoodPlastic Composites Following Exposure in a Soil Block Test. Wood Fiber Sci., 32(3):340-345.


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Borate Wood Preservatives: The Current ... - American Chemical Society

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