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The effects of preservative treatment and exposure to wood degrading fungi on fiber reinforced polymer (FRP) materials used for structural wood reinforcement
2001 - IRG/WP 01-40204
Glass fiber reinforced phenolic (GFRP) composite materials are becoming increasingly accepted for use in the construction industry because they combine advantages of both wood and advanced polymeric materials. Addition of only 1-3% FRP in the tension zone, for example, can typically improve the strength of the hybrid system by 200%. As more applications are found for wood/FRP hybrids, (e.g. laminated wood for bridge applications, waterfront piers) their use in exterior and high-decay-hazard environments would be expected to grow. Since FRPs were designed to be used with wood material for use in exterior exposures, they will be exposed wood preservative chemicals, and to wood decay fungi as well. Therefore, currently developed glass-fiber reinforced phenolic polymer materials for wood reinforcement were examined to determine the effects of wood preservative chemicals and exposure to wood degrading fungi. Several common wood preservative chemicals (oil-and water-borne) were used for treatment of FRP materials. While chemically "fixing" preservatives resulted in significant strength loss, oil-borne preservatives systems did not affect the mechanical properties of the FRP material. When the common brown and white rot fungi (Gloeophyllum trabeum and Trametes versicolor) were used for fungal exposure studies, after 24 weeks of exposure G. trabeum exposed FRP coupons showed reduction in interlaminar shear strength. Scanning electron microscopy (SEM) and fluorescent photomicrograph 58 analysis supported the mechanical test results, indicating that fungal growth and possible consumption of organic sizing material on the wood/fiber interface had occurred. Further studies are underway with different organisms to provide a more detailed explanation of biodegradation mechanisms of FRP composites for wood reinforcement.
C Tascioglu, B Goodell

The effect of oil-borne preservative treatments on the shear strength of FRP/wood composite adhesive bonds
2003 - IRG/WP 03-40265
Reinforcement of structural wood components with Fiber Reinforced Polymer (FRP) will enhance the beam’s strength, but actual data on long-term durability is sparse, not well documented or not readily accessible. In this study, bond properties of FRP-wood composite materials were investigated following treatment with creosote or copper naphthenate preservatives. The properties investigated included stress and the percentage of wood failure experienced in shear (ASTM 1998). When tested in a wet condition (following a vacuum/pressure soak), creosote-treatment adversely affected the wood failure values associated with specimens fabricated with a pultruded FRP composite sheet (E-glass fiber, bonded with urethane). When these tests were conducted with samples under ambient conditions, the shear strength of this material was also adversely affected by creosote. In addition, both creosote- and copper napthenate-treatment adversely affected the shear strength of a SCRIMP™ fabricated FRP material (carbon fiber, vinyl ester matrix).
B Herzog, B Goodell, R Lopez-Anido

Effectiveness and synergistic effects between copper and polymer betaine
1996 - IRG/WP 96-30097
Different formulations of "Copper Amine" and Polymer Betaine were studied. During laboratory tests a synergism between both active ingredients against soft rot and dry rot has been found. The efficacy against soft rot according to the "BAM method" and the European Standard ENV 807 depends only on the amount of copper. Long term tests in a fungus cellar for determining the relative protective effectiveness in ground contact show similar results as CCA-treated wood.
H Härtner, V Barth

Life cycle analysis of utility poles. A Swiss case study
1995 - IRG/WP 95-50040-05
Use of preservative-treated wood products faces increasing public and political pressure because of environmental concerns regarding the chemicals used to protect the wood. However, critics usually focus only on one single aspect of the whole life cycle of treated wood products, disregarding other environmental effects of timber utilization. To evaluate the ecological consequences of wooden utility poles (CCF/CCB impregnated roundwood and glulams) and their alternatives of reinforced concrete and steel, a life cycle assessment was conducted. Based on data from existing Swiss electricity transmission lines, a comprehensive inventory was established of all extractions from, and emissions to the environment caused by each process step. This inventory data was linked to possible environmental impacts using various aggregation methods. An evaluation was made for single poles as well as for whole transmission lines. The results show that impregnated roundwood utility poles in fact have certain environmental benefits when considered over their whole life cycle.
T Künniger, K Richter

The Relationship of Fiber Cell Wall Ultrastructure to Soft Rot Decay in Kempas (Koompassia malaccensis) Heartwoo
2004 - IRG/WP 04-10541
The ultrastructure of fiber walls in kempas (koompassia malaccensis) heartwood was examined in relation to soft rot cavity formation. The fibers consisted of middle lamella and thick secondary wall. The secondary wall was differentiated in to a S1 layer, and a unique multi-lamellar S2 layer. Two distinct forms of lamellae were recognisable, one type being considerably thicker than the other. They also differed in their electron density, the thin lamellae being much denser than the thick lamellae. It was not possible to determine whether a S3 layer also existed, because of the presence of a dense material coating the lumen wall, which obscured the definition of this region of the fiber wall. The resistance to soft rot varied with different regions of the fiber wall, middle lamella being completely resistant and the thick S2 lamellae least resistant. The observed relationship between the ultrastructure of these fiber wall regions and the degree of their resistance/susceptibility to soft rot cavity formation is discussed.
A P Singh, A H H Wong, Yoon Soo Kim, Seung-Gon Wi

Fluoride woodpill
1987 - IRG/WP 3431
Decay problems of spruce joinery in the Netherlands in the 1960's and 1970's led to the introduction of preservative treatment. Because of the known penetration difficulties with Spruce, the results of the treatments were not always successful. The fact that the decay was found only in the joints led to development of the philosophy of "local preservation" of the joints in remedial and preventative treatments, like preservative injections or use of rods and capsules containing preservatives. However the diffusion of the preservatives used in most of these systems is often poor in spruce. Because Spruce joinery dip-treated with bifluorides showed good penetration and protection, a pill consisting of a hydrophylic polymer and bifluorides was developed by TNO. Various laboratory tests carried out with this pill have confirmed good penetration of the bifluorides in the wood and activity against decay fungi.
J W P T Van der Drift, K J M Bonsen

End grain sealants for wood preservation studies
1985 - IRG/WP 3341
The results of tests with possible end grain sealants for wood preservation studies are reported. The epoxy resins used gave satisfactory performance on wet or dry Sitka spruce and have been used with success for diffusion treatment studies.
R J Murphy, N A Summers

Termite Response to Agricultural Fiber Composites: Hemp
2005 - IRG/WP 05-10548
Industrial hemp, Cannabis sativa, is a fiber usable in manufacture of nutritional products, rope, textiles, paper and building products. Due to the illicit recreational uses of Cannabis sativa varieties with high tetrahydrocannabinol content (marijuana), hemp is not grown commercially in the United States. However, it is grown in many other nations, and has been proposed as a replacement for sugarcane and other commodity crops in the United States, including Hawaii. These studies were undertaken to determine the susceptibility of several potential hemp building products to Formosan subterranean termite attack. Although advocates of the fiber sometimes comment on its relative resistance to insects and decay fungi, there is little to no data available to either substantiate or refute these claims. Termite responses to experimental hemp fibreboards (UF or MDI resins), and to a commercial mineralized hemp building material (Isochanvre) were evaluated in laboratory essays. The hemp fibreboards were readily attacked by termites, although the UF resin was relatively toxic to them in comparison to MDI. Termites also readily consumed the mineralized hemp fibers, although mortality was high. Thus, one can conclude that hemp is susceptible to termite attack. Urea formaldehyde resin in fibreboards and silica, lime or boric acid in mineralized hemp were detrimental to termite survival, but still did not prevent significant attack. Preservative or other treatments appear to be required to protect hemp building products from degradation.
J K Grace

Biosynthesis of ß-Glucan microfibrils by cellular fractions from brown-rot fungus Postia placenta (MAD-698 and ME-20) and white-rot fungus Schizophyllum commune (MAD-619)
1993 - IRG/WP 93-10025
In this study, we compared the brown rot fungus Postia placenta (MAD-698 and ME-20) with the white rot fungus Schizophyllum commune (MAD-619) to determine the location and distribution of glucan synthetase. We also measured the soluble protein content in subcellular fractions obtained by differential centrifugation MAD-698 is a degradative isolate, but ME-20 and MAD-619 do not produce significant weight loss in wood. The solubilized enzyme glucan synthetase catalyzes the UDP [U-l4C] glucose to synthesize an insoluble linear 1,3-ß-D-glucan polymer. Glucan is a component of basidiomycete cell walls and hyphal sheath. The wood-degrader MAD-698 showed the most glucan synthetase activity in the mixed membrane fractions, and the nondegradative isolates ME-20 and MAD-619 had the most activity in the cytoplasmic fractions. In fact, glucan synthetase activity was found in different proportions in different particulate fractions of MAD-698, ME-20, and MAD-619. Treatment with a mixture of the detergents octylglucoside and CHAPS ( 3 -[(3-Cholamidopropyl)-dimethylammonio]-1-propane-sulfonate) increased the glucan synthetase activity only in the cell wall fraction.
S C Croan, T L Highley

Termite response to Agricultural Fiber Composites: Bagasse
2005 - IRG/WP 05-10549
Bagasse, or sugarcane rind, is a fibrous by-product of sugar extraction from sugarcane, Saccharum officinarum L. Bagasse fiber performs similarly to hardwood fiber in composite board products. In laboratory studies, Formosan subterranean termites survived as well on a diet of Bagasse as on Douglas-fir wood. Field tests with a compressed Bagasse panel (produced by heat extrusion) indicated that termites readily penetrated the acrylic/vinyl latex coating on the panel, and tunnelled throughout the interior Bagasse fibers. Treatment of the fibers with disodium octaborate tetrahydrate did not prevent the termite penetration of the panel exterior. Subsequent moisture sorption by the fibers led to rapid swelling and deformation of the panels. A dimensionally stable, high density Bagasse particleboard was also evaluated in laboratory tests. No swelling was noted, although the particleboard was readily penetrated and consumed by Formosan subterranean termites, and mold growth was also noted on the test wafers. In recent years, high-profile Bagasse board production facilities were opened in both Louisiana and Hawaii, only to close shortly thereafter. Bagasse may have more market potential in a value-added, preservative treated product than as a low-end commodity competing with comparable wood products.
J K Grace

Low polymer levels containing bioactive monomer polymerized in situ provide resistance to Gloeophyllum trabeum
1995 - IRG/WP 95-30066
Wood preservation based on in situ polymerization of potentially bioactive monomers has been studied. Tributyltin oxide acrylate (TBTOA) and pentachlorophenol acrylate (PCPA) were synthesized. Wood samples were treated at 2, 5, 10, 15 and 20% by weight solutions with varying amounts of crosslinker (trimethylolpropane trimethacrylate, TMPTM) and polymerized in situ in wood samples (2.54 x 2.54 x 0.635 cm³). Methyl methacrylate (MMA) also was run at the same concentrations as a non-bioactive monomer comparison. Soil block testing was performed on acetone leached samples using Gloeophyllum trabeum in a standard ASTM test for 12 weeks. TBTOA was effective at all levels except when using greater than or equal to 10% crosslinker concentrations. PCPA showed some efficacy with 0% crosslinker present, but otherwise it gave no more protection than the MMA controls alone. This is probably due to the stable ester linkage formed in the polymer. Further investigation is underway to synthesize and biologically evaluate new bioactive monomers at low polymer levels for wood protection.
R E Ibach, R M Rowell

Physical and mechanical properties of wood-polymer composites prepared from alder wood (Alnus glutinosa (l.) gaertn. subsp. barbata (c.a.mey.) yalt)
2001 - IRG/WP 01-40201
In this study, the physical mechanical properties of wood-polymer composites prepared from alder (Alnus glutinosa (L.) Gaertn. subsp. barbata (C.A.Mey.) Yalt) wood were investigated. Three different monomers styrene, methyl methacrylate and styrene/methyl methacrylate (70/30) mixtures and two loading levels were used in preparation of wood-polymer composites. Of physical properties, the oven-dry specific gravity, the ratio of water uptake, the water repellent effectiveness and from mechanical properties; the compression strength parallel to the grain were determined. Full loading applications gave the best results for all monomer. The oven dry specific gravity, the water repellent effectiveness and, the compression strength parallel to the grain were found between 0.710-0.950 gr/cm3, 39.45-85.78% and 338.78-645.13 kp/cm2 respectively.
A Temiz, Ü C Yildiz, E D Gezer

On the resistance of consolidated ancient wood against Serpula lacrymans (Wulfen: Fr.) Schroeter
2000 - IRG/WP 00-10348
Structural timbers and other wood objects of cultural value in historical buildings and museums are often attacked by wood-destroying fungi. The aim of conservators is to preserve such damaged timbers and prevent further biodeterioration by impregnation with consolidants. There is little knowledge of the resistance of consolidated timber and art objects to a new attack by wood-destroying fungi. Brown-rotted wood consolidated with acrylic resins, PVA (poly(vinyl acetate)), epoxy resins, shellac, linseed oil, animal glue and a beeswax/paraffin mixture were tested against the brown-rot fungus, Serpula lacrymans. Specimens impregnated with linseed oil and the epoxy resins Araldit BY and Araldit DY did not show noticable mass loss. This was attributed to a high mass gain and even distribution of the consolidants. In contrast, specimens prepared with the acrylic resins Plexigum P-28 and Paraloid B-72 showed approximately 25% mass loss at a mass gain up to 40% because of uneven distribution in the wood. Decreases in mass loss were not proportional to increasing polymer loadings.
W Unger, A Unger, U Schiessl

The Effect on Biological and Moisture Resistance of Epichlorohydrin Chemically Modified Wood
2002 - IRG/WP 02-40224
Southern pine solid wood and fiber were chemically modified with epichlorohydrin to help in understanding the role of moisture in the mechanism of biological effectiveness of chemically modified wood. The solid wood had weight gains from 11% to 34%, while the fiber had weight gains from 9% to 75%. After modification, part of the specimens were water leached for 2 weeks or extracted for 2 hours with a toluene:ethanol (2:1) solution. The equilibrium moisture content (EMC) at 30%, 65%, and 90% relative humidity (RH) and 27 °C was determined on all specimens. Laboratory soil block decay testing using the brown-rot fungus Gloeophyllum trabeum was performed and weight loss calculated. Results show that epichlorohydrin modified specimens did not lower the EMC significantly, yet there was biological effectiveness at 31% weight gain for the solid wood and 60% weight gain for the fiber. This indicates that the mechanism of efficacy may be due to substrate modification rather than moisture exclusion. Energy dispersive x-ray analysis (EDXA) was performed locating the chlorine throughout the wood cell wall.
R E Ibach, B-G Lee

The efficacy of polymer/preservative treatments in soil-bed exposure
1992 - IRG/WP 92-3729
Southern pine was treated with CCA, CCB, sodium borax/boric acid, or disodiumoctaborate, alone or in combination with an acrylic polymer system containing a water repellent. Treated samples were subjected to an unsterile soil burial test. The addition of polymer reduced the weight loss in borontreated samples at the lower retentions but not at the higher retention. Results with borates indicate that polymers may improve performance in above-ground applications. Polymer treatments improved the performance of CCA and CCB at retentions below threshold, indicating the potential for modifying CCA/CCB formulations.
R J Murphy, H M Barnes, S M Gray

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

Effect of aqueous polymer treatments on wood properties. Part 2: Mechanical properties
1990 - IRG/WP 3611
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for static bending, toughness, and hardness were conducted on matched treated and untreated pieces according to ASTM Standards. Properties of pine were not affected by treatment with the polyacrylate. With sweetgum, the modulus of rupture and modulus of elasticity were reduced, while hardness was improved. For the DMDHEU treatment, reduction in property values for both species was related to curing temperature.
Z Ashaari, H M Barnes, D E Lyon, R C Vasishth, D D Nicholas

The durability of wood polymer composites against fungi and insects
2000 - IRG/WP 00-40161
New materials such as wood polymer composites are used more in France. These materials are obtained by mixing wood and thermoplastics in different ratios. These kind of material must be considered as new materials and some characteristics such as durability must be evaluated for outdoor applications. On the other hand, some recycled fibers from wood waste could be used as raw materials. Some woodpolymers have been made in order to prepare some profiles by extrusion process. The wood species used as reinforced materials are beech, spruce, jaboty and limba. The thermoplastics used are recycled polyvinylchloride, polyvinylchloride and polypropylene. The mechanical and physico-chemical properties of some profiles have been characterised. The durability of these wood polymer composites has been evaluated. Significant results on durability against wood-decaying fungi and insects as termites are presented.
G Labat, I Le Bayon, J Gerard, F Amin

End grain sealing by polymer impregnation
1992 - IRG/WP 92-3708
The solution and dispersion characteristics of several hydrophobic derivatives of cellulose have been studied and the abilities of these polymers to afford effective end grain sealing of Corsican pine have been examined. Both solution and dispersion treatments with ethyl cellulose imparted good water repellency and end grain sealing to wood samples, however, the disperse systems possessed lower viscosities. Scanning Electron Microscopy (SEM) of treated samples and polymer radiolabelling/autoradiography studies indicated pit-membrane pore filtration of polymer particles close to the end grain. A range of esters (C2-C18 side chains) of Hydroxypropyl Cellulose have been prepared and characterised (FTIR, NMR). The acetyl, propyl and butyl esters formed coherent, flexible films. The C6, C9, C10 and C11 esters were essentially gums. However, the C18 (stearoyl) ester was found to form strong, wax like films, due to pronounced ester side-chain interactions. A number of the polymers were applied to Corsican pine test samples. Water repellent ability was found to strongly parallel the ability of the derivatives to form coherent polymer films. The C18 (stearoyl) ester exhibited impressive end grain sealing; outperforming all other systems tested at equivalent application levels. This work indicates that hydrophobic polymers that readily form strong films from solution or dispersion afford enhanced end grain sealing as compared to materials that simply produce a hydrophobic effect.
J M Lawther, W B Banks, D G Anderson, J A Cornfield

Three-year field trials of polymeric formulations which provide a new basis for the invention and design of non-toxic wide-spectrum wood preservatives
1994 - IRG/WP 94-40029
Three types of non-toxic polymeric formulations invented using a new approach to wood preservation were challenged with termites and fungi in three-year ground-contact field trials in the sub-tropical climate of Natal. These formulations were copper soaps of carboxylic acid groups of unsaturated fatty acids of waxes and edible vegetable oils; of resin acids of rosin, and, of synthetic unsaturated polyester resins. The formulations self-polymerise within lumena of wood elements after pressure-impregnation and also co-react with carbon-carbon double bonds and aromatic nuclei of lignin. The biocidal mechanism is based on the release of copper by hydrolysis under humid conditions and on the reformation of the same bond on redrying of the treated timber in service. All formulations tested were effective and durable. Rosin formulations at retentions of 0.91 kg/m³ and polyester formulations at retentions as low as 0.4 kg/m³ each out-performed creosote at 37.5 kg/m³.
A A W Baecker, A Pizzi

Effect of aqueous polymer treatments on wood properties. Part 1: Treatability and dimensional stability
1990 - IRG/WP 3610
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for dimensional stability were conducted on matched treated and untreated pieces. Measurement of the antishrink efficiency indicated that DMDHEU was a better stabilizer than the polyacrylate system. Stability was related to polymer retention and curing temperature.
Z Ashaari, H M Barnes, R C Vasishth, D D Nicholas, D E Lyon

A new process for in situ polymerization of vinyl monomers in wood to delay boron leaching
1998 - IRG/WP 98-40110
Efforts were accelerated on effective use of boron compounds in wood preservation owing to their environmentally safe characteristics and relatively low costs in addition to their well-known high bioactivity and fire resistant properties. Although having these unique favorable properties, they are readily leachable from treated wood at humid conditions. Therefore, they had limited market for exterior applications. A supplementary combination treatment with vinyl monomers; styrene (ST) and methylmetacrylate (MMA) was studied in order to extend the service life of boron treated wood. Sapwood specimens of Japanese cedar (Cryptomeria japonica D. Don) first treated with boric acid (BA) at 1.00% aqueous solution concentration. Vinyl monomers were impregnated after air-drying of BA-treated wood at ambient temperatures. Polymerization was performed during compression of monomer impregnated wood to a 50 to 70% dry set of radial dimension under a hot-press heated to the polymerization temperatures of 60 and 90°C required by the selected catalysts VAZO (a, a' - Azobis-isobutyronitrile) and benzoyl peroxide, respectively. Wood acquired a perfect dimensional stability and remarkably high moisture exclusion efficiency with the minimum water holding capacity with the compressed-wood polymer composite (CWPC) process that was approved by submerging of the test specimens in tap water, boiling water exposure to a 10 cycles accelerated severe weathering. As a result, boron leaching rate from CWPC pretreated with BA was considerably slower than that from ordinary WPC. Scanning electron microscope (SEM) observations were found explanatory for controlled-but-continuous boron leaching determined analytically. An effective bulking was found necessary to accompany to polymerization in cell wall with an even distribution of monomer in wood. Grafting to cell wall components can be tried further to achieve an envelop polymerization of boron deposited sites in WPC for better boron immobility.
M K Yalinkilic, W Dwianto, Y Imamura, M Takahashi

The role of oxalic acid in short fiber formation by the brown-rot fungus Postia placenta
1993 - IRG/WP 93-10028
The mechanism by which brown-rot fungi depolymerize wood and cellulose remains a perplexing problem. Current evidence favors oxidation by low-molecular weight, non-enzymatic fungal metabolites. During attack of cotton cellulose by Postia placenta MAD-698, the degree of polymerization (DP) decreases to limit of degree of polymerization (LODP) over a period of 5-6 weeks with relatively low weight loss (circa 20%). Attack by MAD-698 can be accelerated by glucose and gluconic acid. At or below a DP of 350, dispersion of macrofibers was observed in aqueous Triton X-100 (0.1%). Similar dispersion was observed when cotton cellulose was pretreated with 1.0 N oxalic acid prior to colonization with Postia placenta MAD-698 and strain ME-20. The latter is not able to depolymerize cotton cellulose or cause weight loss of wood in soil block tests. The purpose of this paper is to describe the fragmentation of cotton cellulose, with or without pretreatment with oxalic acid, by Postia placenta. We conclude that short fiber formation correlates with depolymerization near to LODP, and that oxalic acid likely contributes to the process without effecting a measurable reduction in percent crystallinity of the cellulosic structure.
F Green III, J M Hackney, C A Clausen, M J Larsen, T L Highley

Micromorphological Characteristics of Degradation in Bamboo Attacked by White Rot Fungus Lentinus edodes
2006 - IRG/WP 06-10575
In comparison with micromorphological works for wood decay, little known is about the decay pattern of bamboos by wood decay fungi. The present work was undertaken to understand the general degradation pattern of bamboo and the influence of polylaminate layers in bamboo fiber walls on the restriction of fungal decay. The weight loss of bamboo species Phyllostachys puberscens against the white rot fungus Lentinus edodes after 16 weeks incubation was around 13%. Degradation was restricted to the parenchyma cells while degradation of fiber and vessel walls was limited. Degradation of bamboo fiber cell wall by L. edodes showed two different decay patterns. At the beginning stage of decay, middle lamellae including cell corner middle lamellae were selectively degraded, leaving the fiber secondary walls. In a certain stage of decay, the secondary wall in bamboo fibers was eroded outward from the cell lumen. Lamellation of bamboo fiber cells restricted the movement of fungal hyphse into next lamellae. Narrow layers in bamboo fiber appeared to influence the direct penetration of fungal hyphae into next layer. Cytochemical examinations exhibited that narrow layers were rich both in lignin and in polysaccharides. Chemical composition and microfibril orientation in narrow layers might influence on the movement of fungal hyphae in the bamboo fibers.
Chang Hyun Cho, Kwang Ho Lee, Yoon Soo Kim

Micromorphology of Bamboo Fibers Degraded by Brown-Rot Fungus Gloeophyllum trabeum
2006 - IRG/WP 06-10576
The decay pattern of bamboo by brown-rot fungus was examined. In addition, the influence of polylaminate structures in bamboo fibers on the restriction of fungal decay was also investigated. The weight loss of bamboo Phyllostachys puberscens by the brown-rot fungus Gloeophyllum trabeum after 16 week incubation was about 25%. Parenchyma cells were severely degraded. Microscopical studies showed that G. trabeum removed the inner part of multi layers while the last layer in the polylaminate secondary walls, corresponding to S3 layer in the tracheids, remained essentially intact. Bamboo fiber walls were degraded at a considerable distance from fungal hyphae. Main decomposition of bamboo fiber cell wall by G. trabeum was similar to other brown-rot fungi in terms of preferential removal of inner part of secondary walls, remaining the last layer in polylaminate layer intact. Cytochemical work showed the production of hydrogen peroxide by the brown-rot fungus G. trabeum and the diffusion into the bamboo fiber walls. The effect of polylaminate structures and lignin levels at the narrow layers on restriction on fungal decay to bamboo fibers was also discussed.
Kwang Ho Lee, Chang Hyun Cho, Yoon Soo Kim

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