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Formation of hydrophobic wood surface by means of thermal treatment and surface modification with alkyl ketene dimer (AKD)
2016 - IRG/WP 16-40738
One of the major shortcomings of wood-based materials compared to technical materials is attributed to their poor dimensional stability in changing climates and in contact with liquid water. Heat treatment induces chemical change with a consequent decreasing of reactivity of the material showing unwanted surface inactivation. Alkyl ketene dimer (AKD) is a widely used sizing agent in papermaking, which serves to reduce the uptake of water into paper and thus ensures e.g. printability. AKD molecules can directly react with hydroxyl group of cellulose forming β-ketoester linkages by esterification. In the present study, AKD has been studied as a potential hydrophobic reagent for thermo-treated and untreated wood. To understand how thermo treatment and AKD influences the wood surface of two native species, (Alnus cordata Loisel and Cedrus deodara Roxb.), the samples were treated in Termovuoto® plant technology at 200 °C for 3 hours and then surface were sprayed with AKD, at 5% of solution. 0.5g/m2 and 1 g/m2 quantity of AKD for each treatment were used. The contact angle measurements and ATR-FTIR analysis on Alder and Cedar of treated and untreated wood were investigated. The main results indicated that the contact angle of aqueous solution against wood was changed during time. Treated alder showed an increase of wettability compared to untreated wood. No effect on cedar wood was depicted. When AKD was used the effect of heat treatment on wettability was negligible. A different chemical behaviour was observed on Cedar wood compared to Alder on both heating and AKD treatment effect.
T Lovaglio, T Meints, L Todaro, W Gindl-Altmutter

The effect of temperature on the rate of fixation of an alkyl ammonium compound (AAC) wood preservative
1984 - IRG/WP 3293
The rate of fixation of an alkyl ammonium compound wood preservative was measured by soaking samples of wood wool in various preparations of the preservative for arbitrary times followed by immediate leaching in water. The wood wool was then analysed for residual preservative. The results indicated that fixation was very rapid and increased at higher temperatures.
P Vinden

Relationship between bond strength and surface characteristics of CCA-treated Douglas-fir
1993 - IRG/WP 93-30008
Chromated-copper-arsenate (CCA) treated Douglas-fir was laminated using a commercial phenol-resorcinol resin. CCA treatment enhanced the water repelleney of wood espeeially in the presence of extractives. However, the shear strength of CCA treated wood was 12% lower in dry condition and 38% lower in wet condition after six cycles of vacuum-pressure test than that of untreated wood. Slight removal of treated wood surface by planer or sander contributed for better adhesion, although it was not enough. The characteristics of treated wood surface was analyzed by X-ray photoelectron spectroscopy (XPS). CCA treatment increased C1 (C-H) and decreased C2 (C-OH), indicating migrated exctractives have enhanced the water repelleney of treated surface. The removal of hydrophobic surface of CCA-treated wood decreased C1 component of C1s spectra on the new surface.
K Yamamoto, J N R Ruddick

Evaluation of an alkyl ammonium compound as a fungicide to control sapstain and mould during diffusion storage
1984 - IRG/WP 3282
An alkyl ammonium compound ('Akzo' ES 255) was evaluated for its effectiveness against mould and sapstain during diffusion storage of boron-treated rubber wood. Though ES 255 at 1.0% concentration was effective against mould (71%) and sapstain (89%) it is less satisfactory compared to 0.5% sodium pentachlorophenoxide against mould (92%) and sapstain (98%).
R Gnanaharan

Low-toxicity DNBP wood preservatives
1987 - IRG/WP 3408
Low and very low toxicity single compound preservatives of both excellent insecticidal and fungicidal activity for interior, extrior and ground-contact applications are presented. These are ester derivatives of alkyl dinitrophenols, in particular of 2-sec-butyl-4,6-dinitrophenol (DNBP) and 2-sec-octyl-4,6-dinitrophenol. These esters, of much lower toxicity than DNBP impart to the treated timber comparable long term durability at much lower mammalian toxicity. These esters are shown in hydrolise to DNBP in the timber, explaining its long term durability.
A Pizzi, W E Conradie, A Jansen, R Vosloo

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

Tests with ammoniacal copper and alkyl ammonium compounds as wood preservatives
1984 - IRG/WP 3299
Formulations based on copper and alkyl ammonium compounds in ammonia solution have been tested in a fungus cellar on Pinus radiata and Fagus sylvatica. This type of products gives promising results as wood preservatives, especially on hardwood and are safe to destroy by e.g. combustion. The best results were achieved with a dialkyl ammonium compound, Cu/octyldecyl dimethyl ammonium chloride (NH3). The optimal weight ratio of Cu/AAC is for Pinus radiata = 0.2-0.4 and Fagus sylvatica = 1.0 based on cost-effectiveness. Fixation and leaching of coppertetrammine are discussed in detail. The leaching of active components from the Cu/AAC/NH3-systems is very low.
C-E Sundman

Improvement of intrinsic properties of wood by chemical wood densification - Hydrophobic aspects and durability aspects
1999 - IRG/WP 99-40149
To improve the intrinsic properties of Scot pine wood ((1) hydrophobic surface and (2) durability), two ways of chemical modification have been tested. The first one is the chemical modification of hydroxyl groups by active substances like diisocyanate compounds with a copolymerization step. The second way is a densification by an impregnation of resins and a gamma polymerisation. This second way is described and discussed in this paper The measured parameters are (1) the hydrophobic properties of the surface based on permeability measurements and (2) the biological durability against wood decaying fungi and (3) the weathering behaviour. Significant results are presented and discussed to promote another way of wood preservation based on densification by resins.
G Labat, Q K Tran, I Le Bayon

Alkyl dimethyl benzyl ammonium chloride: toxicity to Coniophora puteana when formulated in water and organic solvent
1986 - IRG/WP 2250
Results from agar block tests using Coniophora puteana demonstrate that the biological activity of alkyl dimethyl benzyl ammonium chloride is affected by the nature of the carrier solvent in which it is applied. In contrast to some earlier work, an alkyl ammonium compound in organic solvent formulation was identified that had significantly greater activity than its aqueous equivalent. A simple solution of alkyl dimethyl benzyl ammonium chloride in xylene did not exhibit increased activity relative to that of the same alkyl ammonium compound in aqueous solution. The reasons for the differences in performance cannot at present be fully explained.
D P Blow

Effect of amphiphilic antioxidant alkyl ammonium ascorbate on inhibition of fungal growth: Application to wood preservatives formulation
2008 - IRG/WP 08-30466
Amphiphilic surfactants were synthesized from ascorbic acid and different fatty amines and evaluated for formulation of wood preservation products. Characterization of physicochemical properties of the new compounds indicated classical behavior of cationic surfactants. Antioxidant properties, estimated using methyl linoleate oxidation inhibition method, were similar to that of ascorbic acid tested in the same conditions. Growth inhibition assays indicated that amphiphilic dodecylammonium ascorbate is able to inhibit Coriolus versicolor mycelium development, while butylammonium ascorbate deprived of surfactant properties has no effect. This compound was then investigated in the formulation of wood preservation mixtures containing propiconazole and compared to formulation obtained with an industrial surfactant. Biological tests based on the ability of these formulations to protect beech wood blocks exposed to a white rot fungus Coriolus versicolor were carried out under laboratory conditions. Results indicated that use of propiconazole formulation in aqueous solution allows to reduce the quantity of biocide compared to solutions of the same concentrations in ethanol. Protection achieved with antioxidant surfactant was slightly superior to that conferred by conventional surfactant.
C Gérardin , T Koumbi Mounanga, P Gérardin

Chemical modification of Scots Pine Sawdust by mixed anhydrides
2008 - IRG/WP 08-40439
By making react mixtures containing acetic-fatty anhydrides on Scots pine sawdust (SPS) without any solvent or catalyst; we synthesized mixed acetic-fatty esters of SPS. Such mixtures were synthesized by reaction between a carboxylic acid and acetic anhydride. These mixtures were obtained after reaction of acetic anhydride and a fatty acid that yields at equilibrium a mixture of five compounds: acetic-fatty anhydride, acetic anhydride, fatty acid, acetic acid and fatty anhydride. The influence of treatment conditions, temperature, molar ratio, reaction time, and length of the fatty chain on the esterification and on the ratio of grafted acetyl/fatty acyl was investigated. Measurement over 5 minutes of static contact angles (CA) with water permitted to evaluate the water repellency of esterified SPS. CA-values were dependent on the fatty acyl content and independent of the acetyl content. The minimum ester content of the oleoyl group required to obtain permanent water repellency (WR) was 25 mmol.Kg-1. Water vapor adsorption measurements indicated that contrarily to WR, hydrophobicity to water vapor was correlated to the total mass acyl content.
J Peydecastaing, E Borredon, S El Kasmi

Wettability and bonding strength of wood thermally-treated with different combinations of soy oil and chemical additives
2009 - IRG/WP 09-40454
Thermal treatment is a method which has gained wider acceptability as an alternative to the chemical treatment in wood preservation. In order to maximize the benefits of this technique several options have been adopted including the use of soy oil in transferring the heat to the wood. Available information on thermal treatment in general and the oil method in particular show that there are still need for further investigations on the possibilities of improving the available options in order to evolve new techniques. Thermal treatment of three wood species of commercial importance in Canada and North America in general was carried out at in different combinations of soy oil, slack wax and cobalt stain medium. The effect of chemical additives in soy oil during thermal treatment depends on both wood species and the type of additives. The slack wax generally has higher impacts than the cobalt stain and black spruce (Picea mariana) shows more consistent response to the effects of the chemical additives.
L Awoyemi, P A Cooper, T Ung

Adsorption of ACQ components in wood
2010 - IRG/WP 10-30522
To investigate the chemical adsorption capacity of copper-monoethanolamine (Cu-Mea) components on wood, the Na+ cation exchange capacity (CEC) of red pine (Pinus resinosa Ait.) was determined and compared to the adsorption capacity of free Mea and Cu-Mea complexes. The CEC increased with increasing pH. Free Mea adsorption as a function of pH followed the sodium adsorption curve except at pH over 9, when it exceeded the CEC. Cu-Mea adsorbed up to the CEC at pH 9.0-9.5 apparently as Cu(Mea)+, whereas the complex in solution is predominantly of the form Cu(Mea)2+. For the quaternary ammonium compound, alkyl dimethyl benzyl ammonium chloride (ADBAC) adsorption isotherm showed two different adsorption mechanisms into wood: ion exchange reaction at low concentration and hydrophobic interaction at high concentration. ADBAC adsorbed at solution concentrations below a critical concentration (hemi-micelle concentration) had high leaching resistance while ADBAC adsorbed into wood at above the critical micelle concentration (CMC) had low leaching resistance. The CMC decreased with addition of Mea and Cu-Mea. The anion, Cl- of ADBAC was only adsorbed at solution concentrations above the CMC and was easily leached out. The adsorption capacity of ADBAC into wood by cation exchange reaction did not achieve the cation exchange capacity (CEC) of wood. However, the total adsorption of ADBAC and Cu achieve the CEC of wood in the presence of copper amine, and ADBAC competes with copper to occupy the same sites in wood.
Myung Jae Lee, P Cooper

The potential of silicone-based formulations to enhance wood properties through industrial treatment for outdoor use
2011 - IRG/WP 11-30578
High hygroscopicity is one of the main weaknesses of wood as far as its susceptibility to biodegradation, and specifically to fungal decay. New wood preservation technologies are constantly entering the wood protection market, competing with traditional, biocide-based preservation. Silicones are commercially used as hydrophobic agents on stones and concrete. They belong to the restricted number of products that demonstrate a potential to protect wood through non-biocidal chemistry that increase its hydrophobicity. In this study, small Scots pine sapwood and beech specimens (Pinus sylvestris and Fagus sylvatica) were impregnated with silicone solutions in order to assess these solutions’ ability to increase wood hydrophobicity and resistance to fungal decay. Some wettability tests were also performed to gauge the difference in superficial tension of the tested impregnated wood pieces. The same tests also allowed us to determine the depth of the impregnation. The results of the relative water uptake and water repellent effectiveness tests showed that several silicone formulations significantly reduce the water content of wood by either filling the wooden cavities or impeding water absorption. The potential of using the tested silicone formulations to protect wood against decay fungi for outdoor applications is discussed in this paper.
F Simon, F Marchal, F Pochon, M Kutnik, I Le Bayon

Reducing Extractives Stain in Western Red Cedar Sidewall Shingles
2014 - IRG/WP 14-30654
One of the aesthetic challenges that western red cedar shingles face is extractives redistribution stain, particularly in unpainted sidewall applications. Dip and pressure treatments with a mixture of quaternary ammonium compounds and alkyl amine oxides were investigated for their ability to prevent this stain. After nine months of exposure in Vancouver, extractives stain was present on nearly all untreated shingles, but was greatly reduced in incidence and intensity on both the dip- and pressure-treated shingles. Longer-term potential benefits (increased durability) and risks (accelerated weathering) of these treatments should be investigated.
R Stirling

The influence of log soaking temperature and thermal modification on the properties of birch veneers
2016 - IRG/WP 16-40749
In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.
S Källbom, K Laine, M S Moghaddam, A Rohumaa, K Segerholm, M Wålinder

Hydrophilization of wood using a FE-DBD air plasma
2020 - IRG/WP 20-40907
One of the goals of surface protection of wood with coatings is to prevent the evolution of moisture in wood, which accelerates its degradation by abiotic and biotic factors. Good wettability of wood is a necessary pre-condition for sufficient protection with water-based coatings. Treatment of wood surface with atmospheric dielectric barrier discharge in configuration with a floating electrode was shown to be useful technique for enhanced hydrophilicity of wood. The results of treatment process showed that visual and optical properties of the plasma discharge depend on the structural properties of the wood. X-ray photoelectron spectroscopy indicated an increased presence of oxygen containing groups on wood surfaces after treatment with plasma. Promoted surface oxidation further increased the hydrophilicity of wood surfaces, which was detected by water contact angle measurements, gained according to Wilhelmy plate method. It is therefore assumed that the wettability with water-based coatings is also enhanced.
J Žigon, M Petrič, S Dahle

Effect of nano-particle characteristics and concentration on UV protection of timber: A field exposure test
2022 - IRG/WP 22-40941
Wood has a well-known susceptibility to ultra-violet light degradation, leading to premature replacement. A variety of products have been developed to protect against this damage, but most provide less than 12 months of protection and must be regularly reapplied. Developing improved coatings would help reduce wood losses and reduce maintenance costs. Nano-particles have a variety of attractive properties that may make them suitable UV protectants. The effects of nano-particles on surface appearance, colour, and wettability of radiata pine (Pinus radiata) sapwood samples were investigated over 20 weeks of outdoor exposure. Nanometer to micron-sized water dispersions of ZnO, α and γ Fe2O3, rutile and anatase TiO2, Fe3O4, Fe(OH)3, spherical and porous SiO2, and α and γ Al2O3 were used to evaluate the effects of concentration and crystal shape on UV performance. Surface colour changes were characterized by measuring CIE L*a*b* parameters, while surface wettability changes were assessed using water droplet contact angle. Wood appearance changed markedly over the 20-week exposure and mould fungi appeared on the surface. Nano-particles protected wood from photo-discoloration to differing degrees with rutile TiO2 and alpha Fe2O3 providing the most effective protection especially at higher concentrations. Larger micron-sized alpha Fe2O3 provided more sustained UV protection. Mould growth reduced the yellowness on wood surfaces and thus influenced overall colour change. Nano-particles did not reduce wettability of wood after UV exposure. While none of the systems completely prevented UV damage, some showed promise and further trials are underway using combinations of nano-particles.
T Yi, J J Morrell

The influence of thermal modification and surface charring to different levels on wettability of Norway spruce wood
2022 - IRG/WP 22-40942
The wood can alternatively be protected from water absorption by thermal modification and charring. Both techniques cause certain chemical and physical changes in the wood, the extent of which depends on the level of temperature applied. The objective of this study was to determine how the combination of charring to different levels and thermal modification affects the chemical, morphological, and wettability properties of the Norway spruce wood. By charring the wood to four different levels, the carbonization began in the earlywood, continued in the latewood, and finally led to the formation of the cracked, in-depth surface char layer. The study of chemical properties showed that both thermal modification and charring of the wood resulted in dehydration of cellulose and hemicelluloses and promoted the presence of chemical units typical of lignin. The roughness of the natural and thermally modified wood surface increased with the increased level of charring. The surface wettability study showed that a higher level of charring gradually decreased the polar part of the surface free energy for both types of wood. Consequently, the contact angle formed between the wood surface and water increased from 70° to 87° for natural spruce wood and from 75° to 101° for thermally modified spruce wood when the degree of charring was increased. These results provide a good basis for further studies on the influence of the level of charring on the properties of wood surfaces, as well as for future research of this technique for protecting wood.
J Žigon, C Gerardin, M E P Wålinder, P Gerardin

Biocomposites based on PVA, cellulose nanofibrils and tannic acid
2022 - IRG/WP 22-40957
Biocomposite films based on a polyvinyl alcohol (PVA) with the addition of cellulose nanofibrils (CNF) as a reinforcing component and with the addition of the biologically active tannic acid (TA) were prepared. The influence of different additions of CNF and TA in the polymer matrix PVA on the mechanical properties, improvement of hydrophobicity of the prepared films was studied. In all cases, the addition of CNF and TA improved the value of tensile strength and elastic modulus. In one of the prepared films, the hydrophobicity of the film surface was greatly improved compared to the neat PVA film. The better properties of the produced composite films were probably due to hydrogen and ester bonds between the components of the composite, which was confirmed by FT-IR spectroscopy.
U Osolnik, V Vek, I Poljanšek, Poven