Abstract
MethodS FOR DETERMINING MOISTURE CONTENT OF THERMALLY MODIFIED TIMBER BY ELECTRICAL AND ULTRASOUND METHODS
Since first introduced, demand for thermally modified wood products has been steadily increasing. Not only is stability under varying environmental conditions improved, but also decay resistance. However, Jelle van der Beek at the University of Eastern Finland has been investigating how far traditional moisture meters can be used to determine moisture content. Conventional resistance and dielectric meters were compared as well as air coupled ultrasound and electrical impedance spectroscopy. Results show that conventional instruments are not readily calibrated for thermally modified wood, but ultrasound methods were better, while higher precision was possible by combining both ultrasound and electrical impedance spectroscopy.
Moisture content determination of thermally modified timber by electrical and ultrasound methods, Jelle van der Beek, Markku Tiitta, Laura Tomppo and Reijo Lappalainen, pp. 60–66. Figure 1
Jelle van der Beek
THE SCHEFFER INDEX AS PREFERRED METHOD TO DEFINE DECAY RISK ZONES FOR ABOVE GROUND WOOD IN BUILDING CODES
The intention of encouraging innovation in design and construction is very laudable, but the move towards performance based building codes is fraught with danger if the resilience of new products and systems cannot be accurately predicted. Accurate prediction is highly dependent on detailed knowledge of the environmental loads and the product or system capacity. Capacity can be evaluated by accelerated testing, which is itself an uncertain art. How realistic is your test? Have you simply accelerated the test or have you altered it to a different and faster process? Environmental loads from earthquakes, snow and wind are difficult enough to forecast but at least they only involve the relative simplicity of physics. Biodeterioration of treated wood involves physics, chemistry and biology. Before we even try to deal with the wide variation in time to decay for identical untreated replicates under identical exposure conditions caused by biological effects, we can at least attempt to model the effects of climate physics on the average decay rate. There has been a resurgence of interest in this field in the last 10 years. It sometimes seems like every researcher has to disparage previous efforts and come up with their own new and better model so it is refreshing to find two scientists validating Ted Scheffer's original climate index developed almost exactly 40 years ago.
The Scheffer Index as a preferred method to define decay risk zones for above ground wood in building codes, Paul Ian Morris and Jieying Wang, pp. 67–70. Figure 2
Dr Paul Morris
A LONG TERM ASSESSMENT OF PERFORMANCE OF DIFFUSIBLE PRESERVATIVE RODS FOR INTERNAL TREATMENT OF DOUGLAS FIR POLES
The fencing industry will be only too well aware of the premature failure of preservative treated posts made from hard to treat species. The sapwood band is narrow, limiting the width of the pressure treated envelope. Shrinkage in service then opens up fissures so that untreated heartwood is then exposed to fungal and insect attack.
To overcome this problem, diffusible boron and fluoride rods have been inserted into drilled holes in order to provide protection. In this study, Jeff Morrell of Oregon State University presents the results of a study that has been carried out over a 15 year period. Although both preservative types moved well, the study showed that higher dosages and varying treatment patterns would be advisable to achieve a more uniform distribution of the chemicals.
Performance of a boron/fluoride rod for internal remedial treatment of Douglas-fir poles, Jeff Morrell, Connie S. Love and Camille M. Freitag, pp. 71–74. Figure 3
Professor Jeff Morrell
EMISSIONS OF VOLATILE ORGANIC COMPOUNDS FROM KILNS DRYING NORWAY SPRUCE
All those who manage wood drying chambers will be well aware that volatile organic compounds are not only emitted during drying but also from the wood products after drying. In the European Community in particular, standards are being harmonised to control such emissions. Dr Martin Ohlmeyer, Dr Johannes Welling, and Dr Vera Steckel at Johann Heinrich von Thünen-Institute, Hamburg, Germany, investigated the effects of different drying conditions on the product emissions of Norway spruce timber. Emissions were lower when drying was carried out at higher temperatures than at low temperatures. The composition of the emissions was not affected by the drying temperature. Preliminary tests on other spruce samples showed generally higher emissions because of high extractives content induced by stresses in the tree. The results illustrate that the concentration of emitted compounds can vary considerably due to variation in the raw material.
Product emissions of volatile organic compounds from convection dried Norway spruce (Picea abies (L.) H. Karst.) timber, Bottom of FormVera Steckel, Johannes Welling and Martin Ohlmeyer, pp. 75–80. Figure 4
Dr Martin Ohlmeyer, Dr Johannes Welling and Dr Vera Steckel
INVESTIGATION OF POTENTIAL OF SOLUTIONS OF ZINC AND MANGANESE DERIVED FROM BATTERY RECYCLING
Every country is striving to reduce waste and scarce landfill resources so many recycling initiatives are being made. An example of these initiatives collects the huge quantities of primary cell batteries. Dr Claudia Ibáñez of the University of the Republic in Uruguay has investigated the potential for utilising solutions of zinc and manganese, derived from battery recycling, as potential wood preservatives. The results are very encouraging and demonstrate the potential for inclusion in wood preservative formulations where timbers are not exposed to leaching environments.
Wood-preservative properties of a Zn- and Mn- containing solution obtained by a battery-recycling process, Claudia Ibáñez, Mario Rabinovich, Lourdes Silva, Carlos Mantero, Gianna Cecchetto and Maria Pia Cerdeiras, pp. 81–88. Figure 5
Dr Claudia Ibáñez
PRODUCING PULP FOR PAPER FROM OIL PALM TRUNKS USING STRAINS OF FUNGI AS BIOPULPING AGENTS
At one time, unproductive rubber trees were left to decay in the forest. The impact of the utilisation of rubber wood is an example of Malaysian ingenuity in making best use of available resources.
The Malaysian peninsular also has large areas planted for oil palm production. These plantations, in addition to yielding oil, also produce large quantities of biomass that can of course, not only be used for fuel, but also for added value products such as panels and even furniture. Dr Ibrahim Mondal from The University of Sains, Malaysia, has investigated the possible utilisation of oil palm chips by converting them into pulp for paper manufacture. He has used various strains of fungi as biopulping agents to pretreat the chips before mechanical pulping. Although the yield of pulp fell with increased exposure to the fungi, the paper strength improved.
Effect of pretreatment using microorganism on the production of pulp from oil palm trunk, Othman Sulaiman, Nur Hidayah Mohamad, Rokiah Hashim, Mazlan Ibrahim and Ibrahim H. Mondal, pp. 89–94.
THE EFFECTS OF USING NEEM SEED OIL AS FUMIGANT FOR WOOD BORING INSECTS
Fumigants are used internationally to sterilise wood products so as to prevent the transmission of insect pests from one region to another. Reliable synthetic fumigants, such as methyl bromide, have been phased out, so many alternative fumigants are being evaluated. Fumigants originating from plants could have great potential. Dr Himani Pant and Dr Sadhna Tripathi, the Forest Research Institute, Dehardun, India, have investigated the potential of using Neem seed oil for this purpose. Neem seed oil has attracted a lot of interest since many parts of the plant contain many hundreds of terpenoid compounds with medicinal potential. Neem seed oil, when tested as a fumigant against Lyctus africanus larvae, was shown to have both insecticidal and inhibitory effects.
Effect of neem seed oil fumigation on wood destroying insects, Himani Pant and Sadhna Tripathi, pp. 95–100. Figure 6
Dr Sadhna Tripathi and Dr Himani Pant
THE EFFECT OF THERMAL MODIFICATION ON THE MECHANICAL PROPERTIES OF CANADIAN WHITE BIRCH
Birch is a commercially important wood species in the Canadian forest industry. However, it is a perishable species and so treatments that can enhance its durability can extend the range of applications. Amongst the various technical treatments, Duygu Kocaefe and colleagues at the University of Quebec at Chicoutimi (GRTB- Groupe de recherché sur la thermotransformation du bois) have investigated thermal modification. Her paper shows how variations of the treatment conditions affect the mechanical properties, dimensional stability and durability.
Effect of thermal modification on mechanical properties of Canadian white birch (Betula papyrifera), S. Lekounougou, D. Kocaefe, N. Oumarou, Y. Kocaefe and S. Poncsak, pp.101-107. Figure 7
Duygu Kocaefe
STRENGTH GRADING OF NARROW NORWAY SPRUCE SIDE BOARDS IN THE WET STATE, USING FIRST AXIAL RESONANCE FREQUENCY
Softwood timber is usually strength graded in the dry condition. In this interesting paper, Jan Oscarsson and his colleagues investigated whether narrow spruce boards could be graded in the fresh sawn condition using the technique of first axial resonance. The procedure was performed on boards before and after drying and the results verified by mechanical testing. The results showed that wet grading gave results that were as good as after drying.
Strength grading of narrow dimension Norway spruce side boards in the wet state using first axial resonance frequency, J. Oscarsson, A. Olsson, M. Johansson, B. Enquist and E. Serrano, pp. 108-114. Figure 8
Jan Oscarsson
ASSESSING THE PERFORMANCE OF WOOD FILLERS
In the manufacture of wood products, fillers have to be used and proprietary brands are frequently used without considering their performance on varying substrates. The substrates themselves may have different shrinkage properties relative to the filler. In this paper, Joshua Lee Ellis compared two different types of wood filler and assessed their ability to fill voids and assessed the relative shrinkage across varying levels of temperature, humidity and wood species. The research was aimed at improving the production quality of hardwood flooring in western North Carolina whilst eliminating processing extremes in a client's production facility.
Comparison of two wood filler types with respect to relative shrinkage across variations in temperature, in humidity and within wood species, J. L. Ellis and A. Ball, pp. 115-119. Figure 9
Joshua Lee Ellis
SHORT TECHNICAL NOTE ON CHECKING OF FACE VENEERS IN MAPLE PLYWOOD
A common problem in the manufacture of hardwood plywood is fine checking along the grain of face veneers. Scott Leavengood at Oregon State University decided to test the hypothesis that checking would be greater if the loose face were outermost and also whether the application of a clear film forming finish had any effect. After humidity cycling tests, it was found that the application of a finish was found to have no effect, and for panels with the tight side outermost, checking was worse than with the loose side oriented outwards. This is a most interesting observation since it is contrary to normal practice.
A note on face veneer checking in maple plywood, Bottom of FormScott Leavengood, James W. Funck and James E. Reeb, pp. 120–123. Figure 10
Scott Leavengood