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Correlation of %Acetyl and Fiber Saturation in Acetylated Southern Pine Boards
2012 - IRG/WP 12-40598
Wood acetylation represents a chemical modification that increases the hydrophobicity of wood. The level of acetylation in the wood structure determines the extent of hydrophocity with higher levels providing reduced moisture affinity. Due to the reduced hygroscopic nature of acetylated wood, performance features such as dimensional stability, resistance to termites, and resistance to rot and decay fungi are significantly improved. The fiber saturation point (FSP) represents the theoretical moisture content at which wood cell walls are completely saturated with water and no additional water can be absorbed into the wall structure as bound water. The fiber saturation point of acetylated wood is reduced as compared to unacetylated wood also due to its increased hydrophobicity. In this work, the fiber saturation point of a series of 30.5 cm x 14 cm x 2.54 cm acetylated Southern Pine radius edged deck boards with varied levels of acetyl was determined by measuring the width as a function of moisture content. It was found that the fiber saturation point of acetylated wood correlates with the level of acetyl in the wood substrate. A linear relationship is found between these two factors with increasing levels of acetyl providing a reduction in fiber saturation point. The method used to determine the fiber saturation point in this work provides consistent results with that previously determined via an alternate technique. Unacetylated Southern Pine deck boards were also studied in this work and revealed fiber saturation points consistent with prior determinations in the literature and fitted the relationship between acetyl level and fiber saturation point.
J Dickerson, E Cwirko, J Allen

Measurement of Cell Wall Moisture in Acetylated Radiata Pine Using Low-Field Nuclear Magnetic Resonance
2016 - IRG/WP 16-20583
Understanding the interaction of water with acetylated wood is necessary to explain how the protective mechanism of acetylation functions. Low-field nuclear magnetic resonance is one technique for assessing water in wood. Pinus radiata earlywood sapwood samples were acetylated to various weight percentage gains and then analysed with this method. Increased levels of acetylation showed significantly increased T2 relaxation times for free water, indicating that the free water is less restricted. This can be explained by the increase in hydrophobicity of the acetylated cell wall. The fiber saturation point (FSP) was determined using the signal from the cell wall water. The FSP of unmodified samples was 43 ± 2% moisture content and increased levels of acetylation significantly decreased FSP. At high weight percentage gain (~22%) the FSP was 16%, below the 20% threshold for fungal degradation to occur.
H G Beck, C A S Hill

A summary of tests and practical experiences with the Pilodyn wood testing instrument
1980 - IRG/WP 282
This paper presents a summary of the reports, tests and practical experiences with the Pilodyn wood tester not only, however, concerning poles but also in other fields such as standing trees, sawn timber etc. The principle of the Pilodyn is a spring-loaded pin which is fired into the object and the depth to which the pin penetrates is correlated to physical and mechanical properties of the object.
H Friis-Hansen

Decay, decayed wood and the Shigometer
1980 - IRG/WP 281
A L Shigo

Studies on the permeability of Norway spruce (Picea abies)
1987 - IRG/WP 2295
It is well known that the bordered pits play a dominating role for liquid transport in softwoods. The mechanism behind pit aspiration during drying or heartwood formation seems to be well understood. The reason why the fixation of the membrane (torus) to the pit opening remains almost irreversible is, however, still unclear. A technique has been developed combining so-called "solvent exchange drying" with scanning electron microscopy. In this way the pit system can be "frozen" and the number of pits in aspiration can be determined. The technique has been used to widen the understanding of pit aspiration. It has also been used to follow pit aspiration during air drying and in connection with efforts to pit aspirated pits by different physical and chemical methods.
I Johansson, K Nordman-Edberg

Preservative treatment of Gollah cane (Daemonorops jenkinsiana) by soaking method
2001 - IRG/WP 01-40197
The feasibility of preservative treatment of gollah cane (Daemonorops jenkinsiana (Griff.) Mart.) by soaking method was tested in the present study. Cane samples of 1m, 2m and 3m long were soaked with 10% borax and boric acid solution. The study revealed that adequate dry salt retention (DSR) in the above samples could be obtained in 3 days, 4 days and 5 days of soaking, respectively. Within these periods the above rattan samples retained 17.77 kg m-3, 14.97 kg m-3 and 15.00 kg m-3 of dry salt. The DSR values obtained were much higher than those of the specification (4 kg m-3) of Indian Standard. Dry cane (12.87% m.c.) samples up to 3m - 4m long could be treated easily within 5 days, but the same dimension of green (150% m.c.) samples needed 8 days. DSR values of air-dried samples were about 7 times higher than that of the green samples.
M Younus-uzzaman, K Akhter, M H Chowdhury

The effect of initial moisture content on wood decay at different levels of gaseous oxygen concentration
1999 - IRG/WP 99-10316
The influence of initial moisture content on wood decay at different levels of atmospheric oxygen concentration was studied. Three fungi, Coriolus versicolor a white rot, Coniophora puteana a brown rot, and Chaetomium globosum a soft rot, were chosen. The mycelia of the fungi were inoculated on mini blocks of Fagus sylvatica (beech) and Pinus sylvestris (Scots pine). Incubations were under four levels of oxygen concentrations (1, 5, 10, and 21%) at 22°C. It can be summarised that in low oxygen concentrations, increase of the moisture content had a negative effect on the wood decay process in both wood species when exposed to C. versicolor and C. puteana Basidiomycetes). In air, the effect of initial moisture content on wood decay by these fungi corresponded to the fungi characteristics and the wood species. When used C. globosum (soft rot) as coloniser, increasing moisture content generally caused weight losses to be increased (specially in beech). However, when in wood blocks the moisture content was increased, more sporulations of C. globosum were also observed on wood samples.
S M Kazemi, D J Dickinson, R J Murphy

Moisture correction for ultrasonic MOE measurements above fibre saturation point in Scots pine sapwood
2006 - IRG/WP 06-20333
There is a high correlation between methods for dynamic modulus of elasticity (MOEdyn) and static modulus of elasticity (MOEstat). MOEdyn methods have been found sensitive to detect early stages of decay and may be seen as an option for non-destructive wood durability testing. As the MOEstat measurements do not change after reaching the fibre saturation point, the uncorrected MOEdyn data from ultrasonic pulse excitation method provides increasing values after fibre saturation. This is due to the effect of free water in the cell lumen on ultrasonic waves. The aim of this study was to make a moisture calibration for the MOEdyn ultrasonic pulse excitation method using Scots pine (Pinus sylvestris L.) sapwood samples. MOE was measured at five different moisture levels. Three different MOE test methods were used: MOEdyn using ultrasound and vibration excitation and the traditional MOEstat. Sound Scots pine sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated, using untreated sapwood samples as control. In this study a correction value ("k") was calculated based on data from different moisture levels for water saturated samples using four different wood treatments and control. By measuring MOEdyn ultrasonic at wood moisture contents just below fibre saturation point, a minor effect of incipient water accumulation in the wood matrix was detected. Wood treatments influence the "k" value, and a "k" value needs to be calculated for all wood treatments when measuring MOEdyn ultrasound above fibre saturation. All the three MOE test methods in this study are applicable for all wood moisture levels as long as a "k" value is calculated for MOEdyn ultrasound above fibre saturation.
E Larnøy, G Alfredsen, H Militz

Point sur la réglementation et contraintes administratives
1990 - IRG/WP 3575
J H Moneger

Technique for monitoring absorption during a vacuum pressure process
1992 - IRG/WP 92-3696
A laboratory technique was developed and an apparatus constructed which allowed for the direct and continuous measurement and observation of volumetric uptake of water-borne preservative into wood samples throughout a controlled vacuum-pressure treatment process. Fractional filling of void space was calculated. Graphing (fractional saturation) against time allows prediction of optimum cycle lengths with respect to achievable saturation values. Treatability evaluations using this technique were carried out on heartwood samples of six Malaysian hardwood species, kapur, kempas, keruing, punah, rubberwood, simpoh and on sapwood samples of Scots pine as a control. Generally the graphs exhibited two quasi-linear zones showing rapid initial absorption followed by slow absorption over a long period.
A J Pendlebury, J A Petty

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

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

Environmentally more acceptable solvents
1979 - IRG/WP 3131
The subject of this paper is hydrocarbon solvents with particular reference to the cyclo-aliphatic or naphthene-rich, grades which are now available. The specialised low aromatic high boiling petroleum fractions are also discussed.
A M Cumbers

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

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

Effect of point of preservative addition on the mechanical and physical properties of strandboard treated with Tanalith 3485
2000 - IRG/WP 00-40152
Preservative has been added to a PF bonded strandboard at various different stages in the manufacturing cycle and the physical and mechanical properties of the boards have been evaluated (modulus of elasticity, modulus of rupture, thickness swelling, water absorption, internal bond strength, and shear strength). Preservative addition has been examined at five different stages namely green strand diffusion, strand vacuum treatment, glue-line addition, heat and cold quench and by post manufacture vacuum treatment. The treatment methods had marked effects on the mechanical properties of the boards. The post manufacture vacuum treatment at 3% resin content boards showed poor IB strength after wetting but a higher resin content improved the IB strength but did not reduce thickness swelling significantly. Glue-line treatment was done by spraying wood strands with preservative prior to resin blending and this produced boards with inferior physical properties to the other application methods fully evaluated. Higher pressing temperatures alleviated this. Vacuum pressure impregnation and diffusion treatments of the strands prior to pressing produced boards with similar properties to the control boards, produced without preservative addition. A heat and cold quench treatment was used to simulate the immediate treatment of hot boards by dipping after release from the hot press in a production line. This treatment gave properties slightly inferior to the control boards and a poor preservative distribution. The preservative distribution in the vacuum treated strands strandboard and the diffusion treated strands strandboard was uniform.
G J Goroyias, M D C Hale

Investigation of extracellular mucilaginous material in some wood decay fungi
1996 - IRG/WP 96-10188
The external morphology of the extracellular mucilagenous material (ECM) produced by Coriolus versicolor and Coniophora puteana during colonization of Scots pine and beech was studies using SEM. Specimens were examined in the frozen hydrated, freeze-dried and critical point dried state. All technics produced artefacts but the ECM was best preserved when examined the frozen hydated state. Critical point drying damaged the ECM extensively but was useful in partly explaining its nature. ECM was found to line much of the lumen and coated aerial fungal mycelium. Some morphological patterns in which the ECM and fungal hyphae were involved are also descibed.
A R Abu, D J Dickinson, R J Murphy

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

Gelatin encapsulated fumigants for wood fumigations: Current research status
1985 - IRG/WP 3336
The fumigants chloropicrin (trichloronitromethane) and methylisothiocyanate (MIT) were encapsulated in gelatin as an alternative to liquid fumigant treatments for control of decay fungi in wooden utility poles. Gelatin-encapsulated MIT was stored for over 2 years under dry conditions without significant fumigant leakage. Gelatin encapsulated MIT and chloropicrin were released from capsules when placed in wood above the fiber-saturation point, although capsules were more permeable to MIT than chloropicrin. In field treatments, the addition of small quantities of water along with capsules was sufficient for fumigant release. Encapsulated MIT and chloropicrin treatments effectively reduced decay fungus populations in Douglas-fir utility poles.
A R Zahora, M E Corden, J J Morrell

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

The risk assessment process. Point of view of a biocide manufacturer [Évaluation du risque. Point de vue d'un fabricant de biocide]
1990 - IRG/WP 3568
Risk assessment is an inherent part of our everyday lives. The risk assessment equation combines Hazards and Exposure. For the Wood Preservation Industry, the hazards may be characterised by the toxicity a the ecotoxicity of chemicals and the exposure by the identification of exposed people, of the exposure routes and exposure frequency. To quantify the exposure, good co-operation is required between the manufacturer, the formulator and the end user. In the absence of exposure data, mathematical models can be used to estimate exposure using worse case scenarios. Having established the risk associated with a product or process, the manufacturer should work with the end-user to establish and communicate risk management practices.
D Baur

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

Effect of fiber type and content on the natural durability of wood flour/high density polyethylene composites against rainbow fungus (Coriolus versicolor)
2007 - IRG/WP 07-40387
In order to evaluate the effect of fiber type and content on the natural durability of wood flour/high density polyethylene (HDPE) composites against Coriolus versicolor, samples containing 25% and 50% by weight of various natural fibers and HDPE were selected. Natural fibers included in the study were wood flour, rice hulls, hemp fibers and newsprint. Samples containing 25% and 50% natural fiber had 1% and 2% compatibilizer (Maleic anhydride polyethylene (MAPE), respectively. Physical and mechanical properties of all specimens including water absorption, flexural modulus, flexural strength, impact strength and hardness were determined prior to and after incubation with the fungus for 14 weeks at 25 0C and 75% relative humidity. Weight losses of the specimens were also determined after incubation. Results indicated that samples containing 50% natural fiber were more susceptible to fungal decay as compared with those with 25% fiber. Rice hulls proved to be the most vulnerable natural fibers as nearly all mechanical properties of rice hulls composites significantly declined after contamination by the fungus.
A Karimi, M Tajvidi, S Pourabbasi

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