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A practical method to evaluate the dimensional stability of wood and wood products
1990 - IRG/WP 2342
This paper presents a new simple method to evaluate wood and wood products for their resistance to swelling and to assess wood preservatives for their ability to dimensionally stabilize treated wood exposed to water. Permeable wood of various dimensions and treated with different preserving chemicals have been measured for swelling in the radial and tangential direction during immersion in liquid water. The results indicate that a simple exponential function describing the dimension of the samples during immersion can be used to evaluate both the water-repellency and anti-swelling effectiveness of wood preserving chemicals. The results can be achieved in reasonable time, and the parameters of the function can be determined by a commercial desk-top computer program.
J P Hösli

Physical and biological properties of albizzia waferboards modified with cross-linking agents
1995 - IRG/WP 95-40043
Chemically-modified low-density waferboards with cross-linking agents were produced using a fast-growing species of hardwood albizzia (Paraserienthes falcata Becker) as a raw materials and isocyanate resin as a glue adhesive. For the chemical modification, the vapor-phase formalization of the boards and the pad-dry-cure treatment of wafers with cross-linking agents were employed. The vapor-phase formalization was conducted for 5, 10 and 24 hours using tetraoxane as a source of formaldehyde, and the pad-dry-cure treatments with glutaraldehyde and ethyleneurea compound (DMDHEU) were made after impregnation of their 5 and 10% aqueous solutions of each chemical. Sulfur dioxide was used as a catalyst in both treatments. About 70% of antiswelling efficiency (ASE) was gained in all treated boards irrespective of reaction time or solution concentration. All treated boards were very stable to water soaking even in the 2-hour boiling on thickness swelling as well as linear expansion. Laboratory tests with brown-rot and white-rot fungi revealed that decay was completely suppressed in formaldehyde-treated boards, and small losses in weight were counted in other treated boards. All treated boards were also effective in resisting to the attack by the destructive termite Coptotermes formosanus.
S Yusuf, Y Imamura, M Takahashi, K Minato

Improvement of some technological and biological properties of poplar wood by impregnation with aqueous macromolecular compounds
1992 - IRG/WP 92-3721
Poplars (Populus spp) belong to the most important tree species in afforestation programs of the Netherlands. Due to their rapid growth, the wood quality is usually low. Therefore, studies were performed to elucidate whether some technological properties and the resistance against fungal attack could be improved by impregnation with water-soluble resins. The results showed that swelling and shrinkage of poplar wood may considerably be reduced by a treatment with certain resins. The anti-shrink efficiency (ASE) strongly depends upon the resin type. An air-curing alkydresin based on polybutadiene and an air-curing acrylate modified alkydresin emulsion caused the best effects. Additions of wood preservatives to the resins further improved the ASE. Some disadvatages of the tested resins may be seen in their leachability with consequent loss of the dimension-stabilizing effects. The resins by themselves don't reveal fungistatic properties but an impregnation of poplar wood with these materials led in all cases to a better durability against Coniophora puteana and Coriolus versicolor. Leaching procedures influenced the durability in various ways. With resin/fungicide combinations, a good resistance against Coriolus versicolor could be reached even after leaching. SEM and EDXA methods were used to localize the resins in the cell walls and lumina and to detect the growth of mycelium in the specimens.
R D Peek, H Militz, J J Kettenis

Influence of different resin treatments on the dimension stability of wood
1997 - IRG/WP 97-40090
The dimension stability of wood is considered to be an important contribution to its durability and its performance in practice. A number of different treatments have been developed to improve the dimension stability of wood. One applied method is the treatment of wood with monomers or resins. The application of appropriate impregnation conditions seemed to be essential to enhance the efficiency of the treatment with water based resins. Therefore, wood samples of the three wood species Pinus sylvestris L., Pinus radiata D. Don. and Fagus sylvatica L. were impregnated with four different resin systems to evaluate the influence of different parameters on the anti-swelling efficiency (ASE). Variation in diffusion time, initial moisture content and resin concentration revealed considerable differences in retention of the resins and the ASE.
M Sailer, A O Rapp

Diffusion into and bulking of the wood cell wall with polystyrene glycols (PEG)
1991 - IRG/WP 3660
The diffusion and equilibrium distribution of polyethylene glycol (PEG) in the cell walls of red pine (Pinus resinosa) and trembling aspen (Populus tremuloides) were followed by analysing the free lumen solution concentration of vacuum treated wafers at various times after treatment. PEG was more-or-less excluded from the cell walls of wood, depending on the wood species and PEG molecular weight. However, the wood was bulked to a high extent, even with high molecular weight PEG. In aspen, Anti-Shrink-Efficiencies (ASE) of 66, 70, 66 and 58% were achieved with 20% solutions of PEG with nominal molecular weights of 200, 1000, 3350 and 8000 respectively.
P A Cooper, Y T Ung, D Alexander, C Holzscherer

Water-based silicones on wood
1997 - IRG/WP 97-30144
Five waterbased silicones commonly used on masonry where tested as water repellents for wood. The Water Repellent Effectiveness was determined by swellometer-tests and by measuring the water uptake of samples after 24 hours complete immersion and by immersion in a water level of 4 mm for 24 hours. The different methods are compared and discussed. Artificial and natural weathering was performed to determine the durability of the water repellency. Non of the tested silicones showed a significant ASE. The gluability of three tested silicones with PVAc gave poor results. One of the silicone microemulsions and one silicone emulsion performed a water repellency that might allow their use on wood. Two commercial non silicone water repellents that where tested as controls had a lack of durability after weathering.
D Lukowsky, R D Peek, A O Rapp

Investigation of the suitability of silver fir (Abies alba Mill.) for thermal modification
2004 - IRG/WP 04-40275
In this study the suitability of silver fir (Abies alba Mill.) was examined for thermal modification. Comparative experimental investigations were performed with silver fir and Norway spruce (Picea abies Karst.) after thermal treatments. Besides properties, which characterize the quality of heat treatments, like dimensional stability and resistance against fungal attack, strength properties of the heat treated material were tested, i.e. bending strength, modulus of elasticity (MOE), impact bending strength and resistance to abrasion. Silver fir was found to be slightly more suitable for thermal modification than spruce, when treated at 180 °C, whereas thermal modification at 220°C showed a comparable suitability for both species. Advantages of silver fir were found for its impact bending strength, durability, and formation of cracks after weathering.
C Brischke, A O Rapp

Influences of the hydro-thermal treatment on physical properties of beech wood (Fagus orientalis)
2005 - IRG/WP 05-40303
Influences of the hydro-thermal treatment on physical properties of beech wood were studied. Wood specimens (2×2×2cm) were treated in two steps. At first step, samples were treated at 160,180 & 200ºC for 4, 5 & 6 hours. At second step, treated samples were cured based on their first step treatment temperatures (160,180 & 200ºC) for 16 hours. The treated samples were soaked in water and oven dried for 24 hours. The soaking-drying cycles were repeated for seven times. Oven dried density (initial and final), swelling (initial and final), water absorption (initial and final) and density loss were analyzed. Results revealed that swelling was decreased due to the hydro-thermal treatment; while the water absorption was increased in wood. And oven dried density was slightly lost due to the treatment. The density loss and increase of water absorption are related to initial pyrolysis of wood which consequences with increase of wood porosity due to the treatment.
B Mohebby, I Sanaei

Dimensional stabilization and decay resistance of wood treated with brown-rotted lignin and copper sulfate
1990 - IRG/WP 3608
The objective of this study was to evaluate the potential usefulness of brown-rotted lignin (BRL) as a dimensional stabilization and copper complexing agent for wood treatment. For dimensional stabilization, aqueous solutions of the lignin extract were combined with either copper sulfate, glyoxal or other additives. Anti-shrink efficiency (ASE) values as high as 42% were obtained with wood treated with a BRL/Cu combination. By treating wood with a 6% solution of the lignin extract prior to treatment with copper sulfate, a two-fold increase in fixation of copper was attained. Soil block tests were also performed on wood treated with BRL and copper sulfate individually as well as in combination; it was found that the BRL increased the activity of Cu against Poria placenta.
L Jin, D D Nicholas, T Schultz

The use of natural and synthetical tannins to improve the dimensional stability and durability of beechwood (Fagus sylvatica)
1993 - IRG/WP 93-30016
Synthetical tannins and natural extractives of oak, spruce and chestnut have been combined with different fungicides to make the wood more dimensionally stable and more durable. The anti-shrink-efficiency and the improvement of the durability of different synthetical and natural tannins have been evaluated. The results make clear, that an application of the mentioned agents for common use cannot be recommended without further preface. Under "moist" conditions (high relative humidity) none of the tested tannin/preservatives seem suitable for the treatment of beechwood. All the combinations of tannins and preservatives are hygroscopic and poor in fixation and therefore leach quickly. The result of the soil block test too, (approx. 15% weight loss of specimens at relative high loadings of preservatives) is not sufficient to recommend application. Further research has to demonstrate, whether with softwood species better results can be achieved. Furthermore, different concentrations of the most promising agents (tannins and chromium containing salts) have to be tested to determine optimum retentions and toxic values before and after leaching. A considerable improvement of the dimensional properties (ASE 50-75%) was obtained by a treatment with Tannin AKF in ranges of low relative humidities (0-60% RH). Under these dry conditions, however, no fungicides are needed.
H Militz, W J Homan

Biological resistance of furfuryl alcohol-treated wood
1992 - IRG/WP 92-3703
Biological resistance of FFA (furfuryl alcohol)-treated wood was investigated in relation to the rise of ASE (anti-swelling efficiency) resulting from the treatment. Sapwood blocks of Japanese red pine, cedar and beech were vacuum-impregnated with various concentrations of aqueous FFA solutions to get the target levels of% (w/w) RL (resin loading). Air-dried blocks were kept in an oven at 120°C for 8 hours to insure the resin formation submerged in water for 1 week to leach away the unpolymerized portion, re-dried, and exposed to decay fungi and termites. The treatment was more effective for pine and cedar than for beech to enhance their decay resistance. As in cases of chemical modification, the treatment was more effective against white-rot fungus Coriolus versicolor than brown-rot Tyromyces palustris. The required RL to reduce the decay by Coriolus versicolor to less than 3% weight loss was ca. 20% for both softwoods but it was ca. 30% for Tyromyces palustris. FFA-treated woods were less attacked by a destructive subterranean termites Coptotermes formosanus and caused their higher mortality with the increase of RL. The pretreatment of boric-acid impregnation yielded the higher ASE and biological resistance at the lower RL than those of sole FFA-treatment. Decay by Coriolus versicolor virtually eliminated even at 0.5% RL for the treated pine and cedar subjected to the boric acid pretreatment.
J Y Ryu, Y Imamura, M Takahashi

Quantification of methylene bis thiocyanate in wood and its effect on a sapstain fungus Ophiostoma floccosum
2006 - IRG/WP 06-10591
The mobility and concentrations of MBT at different depths of wood billets (200 mm long, 40 mm in diameter) were determined using NMR spectroscopy and ICP-ASE, and then correlated the effect of wood MBT concentrations on growth of O. floccosum in a bioassay using stereomicroscopy and confocal laser scanning microscopy (CLSM). The 13C NMR spectra showed the presence or absence of MBT in wood but was unable to detect small concentrations. ICP-ASE however, produced quantitative data across the depth (40 mm) of the wood billets tested. Within 7 days of storage, MBT penetrated from surface to pith but showed significantly higher concentrations of MBT in surface wood compared to pith wood. Present study highlighted the benefit of using CLSM for fungal detection in wood. The information obtained from the ICP-ASE and the CLSM analysis suggested that to inhibit growth of O. floccosum, the MBT concentration needs to be greater than 55 ?g/g of dry wood. Due to its high detection capacity, ICP-ASE is identified as an excellent tool for MBT detection and quantification in wood.
T Singh

Evaluation of Water Repellency of Treated Wood Using Several Alternative Methods
2009 - IRG/WP 09-20419
In this study, the results of water repellency testing using a digital swellometer method for water-borne organic-preservative systems with water repellent additives are reported. The findings suggest that the traditional method of using matched untreated controls as a reference developed from historic solvent-based treatments for determination anti-swelling efficacy (ASE) may underestimate the actual effectiveness of a given water repellent (WR) system in water-borne treatments. The results show that using a water-treated control may provide a more accurate measurement of the water repellency with any given water repellent additive system for water-borne preservatives. The potential of using data generated from digital swellometer testing are also discussed. These outcomes include water resistance performance monitoring for commercial products, providing indications of the system differentiation in terms of formulation chemistries and their subsequent influence on the water repellency, developing practical guidance and prediction of performance for the WR use-level based on the intended applications, and using characteristics of the swelling curves to estimate important information regarding any dimensional stability imparted by the treatments.
L Jin, A F Preston

Estimating the heat treatment intensity through various properties of thermally modified timber (TMT)
2009 - IRG/WP 09-40459
The suitability of different measures for prediction of the heat treatment intensity was investigated. Therefore, the resistance to impact milling (RIM), the lightness L*, the equilibrium moisture content (EMC), the anti swelling efficiency (ASE) and the total amount of soluble carbohydrates (TSC) of heat treated specimens were correlated with corresponding fungal resistance achieved by heat treatments. Heat treatment temperatures of 180°C, 200°C, 210°C, 220°C, and 240°C for various heat treatment durations from 0.25 to 72 h were applied. The results show, that the decrease in mass (dm) by heat treatments is a suitable measurand to describe the treatment intensity, which is a product out of treatment temperature and duration, where the impact of temperature is predominating the impact of time. The properties examined showed a strong reciprocally proportional relationship with the decrease in mass. Thus different correlations were found for the various treatment temperatures: The higher the temperature applied, the lower was the decrease in mass required for an equivalent improvement of certain wood properties, e.g. biological durability, EMC, and dimensional stability. However, mass loss by Poria placenta correlated well with the resistance to impact milling (RIM), lightness L*, EMC, ASE and TSC of the different heat treated specimens, depending on the heat treatment temperature. Consequently, a reliable estimation of improved fungal resistance of TMT, as well as the quality control of TMT in general, strongly requires certain process information.
C R Welzbacher, C Brischke, A O Rapp

Improvement of the biological performance and dimensional stability of two tropical woods by thermal modification
2012 - IRG/WP 12-40605
Pink cedar wood and rubberwood were thermally modified at 230°C in air for 4 h or for 8 h, and then subjected to bending, compression and hardness tests to evaluate the effect of the treatment on these mechanical properties. The biological performance of the modified wood was also determined, according to EN113, and the dimensional stability measured by means of the anti-swelling efficiency. The thermal modification afforded increased decay resistance and improved the dimensional stability of these tropical woods, at the expense of significant reductions in the Modulus of Rupture and the Work at Maximum Load in the bending test. The reduction in bending strength and in resilience was not significant at the limit of proportionality though; the modified material is hence deemed as suitable for non-structural applications where the occurrence of sudden loads shall not lead ultimately to human harm. Color changes resulted in aesthetic enhancements on these two wood species, particularly so in pink cedar wood. These color changes were readily exploited for the multivariate prediction of all properties studied in this work, including the decay resistance of thermally-modified wood.
M M González-Peña

The effect of acetylation on physical properties of beech (Fagus orientalis) and Alder (Alnus subcordata) wood
2016 - IRG/WP 16-40759
In this study the effect of acetylation on physical properties such as water absorption, volumetric swelling and anti-shrink efficiency (ASE) of beech and alder were investigated. After 24 hours soaking in acetic anhydride, in order to achieving two surface of weight gains, acetylated samples were heated in oven at 120 0C for 90 and 360 minutes. Then water absorption and dimensional stability in terms of volumetric swelling percent and anti-shrinkage efficiency was determined. Physical properties of samples improved by increasing degree of acetylation with considerable decreasing in Water absorption during 24 h soaking in water, that for beech and alder were about 39.2% and 36.6% less than control at highest modification level, respectively. Volumetric swelling of beech and alder treated specimens at 90 and 360 minutes modification was about 55.8, 62.5, 64.2 and 72% less than control, respectively of time. ASE of samples treated in 360 minute has greatly increased.
M Akhtari, M Arefkhani