Leachability and termite resistance of wood treated with a new preservative: ammonium borate oleate

Synthesis of a new chemical compound combining water-repellence of oleic acid and biocidal effect of boric acid linked by ammonia have been followed and validated by fourier transformed infra red (FTIR). This compound named ammonium borate oleate (ABO) has then been studied as a wood preservative. Different molar ratios of oleic acid have been involved in the synthesis of ABO and leachability of those mixes from wood observed according to Japanese industrial standard. The formulation one mole of boric acid and one of ammonia (1:1:4) for four moles of oleic acid has shown the best efficiency compared to formulations 1:1:1, 1:1:2 and 1:1:3 with about 52% of boron remaining after weathering when other formulations retained respectively 10%, 29% and 46% of boron in the case of an impregnation of Cryptomeria japonica. Seven solutions of 1:1:4 ABO in ethanol of different concentrations were then produced and sapwood blocks of C. japonica and Fagus crenata were impregnated. A toxicity threshold of around 2.0 kg/m³ for both species was determined in a termite resistance test to Coptotermes formosanus indicating the positive effect of combining water repellent and biocide. Termite mortality recording and microscopic observations complete this study indicating that the action mechanism of ABO is providing a water resistant inner coating.     

High performance tannin resin-boron wood preservatives for outdoor end-uses

Fixation of boric acid as a low toxicity wood preservative to decrease markedly its leachability was undertaken. Preservative systems based on the cross-linking and hardening of condensed tannins by hexamine, where boric acid is complexed onto the network, were found to markedly slow down the leaching of boron. They significantly enhanced wood durability before and after leaching once tested towards basidiomycetes according to the guidelines of EN 113. A particularly virulent fungal species was used for the tests. Further immersion of the wood so treated in hot unsaturated vegetable oil does yield comparable results.     

Improvement of fungicidal properties and copper fixation of copper-ethanolamine wood preservatives using octanoic acid and boron compounds

Copper ethanolamine preservatives are one of the most important solutions for wood preservation. As copper itself can not ensure sufficient protection against wood destroying organisms we combine it with other co-biocides like quaternary ammonium compounds, azoles and/or boron. Influence of different boron compounds and octanoic acid on copper fixation as well as performance of spruce wood impregnated with different copper/ethanolamine/boron based aqueous solutions is described in this paper. Copper fixation was determined according to the modified ENV 1250 (1994) standard method, while performance against Antrodia vaillantii, Gloeophyllum trabeum and Trametes versicolor was tested according to the mini block procedure. The results showed that addition of boron increases copper leaching, but on the contrary improves performance against wood decay fungi. On the other hand, addition of octanoic acid improves copper fixation, and slightly decreases resistance against copper tolerant fungi.     

An economical treatment schedule for boron impregnation of Eucalyptus grandis wood: Commercial trial of partially dried material

Being non-durable, Eucalyptus grandis wood needs treatment with preservative chemicals. As vacuum-pressure impregnation treatment being more suitable for commercial applications, and boron chemicals being environment-friendly for indoor uses, an economical treatment schedule (15 minutes initial vacuum of -85 kPa followed by a pressure of 1300 kPa for 15 minutes and a final vacuum of -85 kPa for 5 minutes) developed at the Kerala Forest Research Institute was tested for its commercial suitability for treating E. grandis wood with boron chemicals. A pooled mean dry salt retention (DSR) of 7.7 kg m ^-3 was achieved for wood in partially dried condition with average moisture content of around 32%, using a 6% boric acid equivalent (BAE) solution. This confirms the success of the schedule for commercial application, as the DSR achieved is much higher than the standard specification of many countries.     

The boron fixation to the cellulose, lignin and wood matrix through its reaction with protein

This paper is an attempt to determine the actual boron adsorption and retention in wood and its isolated components: cellulose and lignin. The rate of boron retention in cellulose, lignin and wood powder of Scots pine Pinus silvestris L. was investigated using denaturing properties of protein contained in reaction solutions. Both animal and plant origin protein was used in this study. In order to determine the reactivity of the analyzed formulation the reactions of cellulose, lignin and wood powder with protein borates were carried out. The aim of the analyses was also to compare methods of protein denaturation: thermal and chemical with the use of tannic acid solution. The obtained products were subjected to water extraction at 20 °C. Boron content in the solid and water extracts was analyzed using atomic absorption spectrometry (AAS). The results showed that the method of protein denaturation played the crucial role in the rate of boron retention. The type of protein used in the reaction solution had also significant effect on the boron retention.     

Effects of N′-N-(1, 8-Naphthalyl) hydroxylamine (NHA-Na) and hydroxynaphthalimide (NHA-H) on boron leachability and biological degradation of wood

Although boron wood preservatives have many advantages, boron itself does not adequately protect wood in ground contact and exterior applications because its susceptibility to leaching. As a result of previous studies to limit or decrease boron leaching, several fixation systems have been developed. In this study, we evaluated the effects of N′-N-(1, 8-Naphthalyl) hydroxylamine (NHA-Na) and hydroxynaphthalimide (NHA-H) on boron leaching and decay and termite resistance via possible boron precipitation in wood after NHA treatments at varying concentrations. Results showed that treatment of wood blocks with disodium octaborate tetrahydrate (DOT), boric acid (BA), or calcium tetraborate (CaB) incorporation with 1.0% NHA-Na solutions in sequential processes appears to somewhat reduce the susceptibility of boron to leaching. Blocks treated sequentially with boron compounds and then 1.0% NHA-Na solutions showed about 30% less boron leaching compared to boron only treated blocks. In addition, the existence of boron and NHA-Na in wood together showed a synergistic effect against brown-rot fungus, Fomitopsis palustris. We conclude that the relationship between boron and NHA-Na concentration in wood as regards precipitation possibilities appears to be predictive for reducing boron leachability.     

Effect of hot air post-treatments on copper leaching resistance in ACQ-D treated Chinese fir

Chinese fir (Cunninghamia lanceolata Hook.) wood cubes (19?×?19?×?19 mm³) were treated with amine copper quat-type D (ACQ-D) solution and fixed with different hot air post-treatments. The effects of temperature, relative humidity, duration, air circulation of post-treatment as well as the copper retention in the treated wood on copper leaching were investigated. With the help of ultraviolet or visible spectroscopy (UV/VIS), the valence conversion of copper in treated wood post-treated with optimal post-treatment conditions was investigated, and its relation with copper leaching was also discussed. The results showed that besides temperature and relative humidity, air circulation during hot air post-treatments also had a significant effect on accelerating copper fixation in ACQ-D treated wood. 70 °C, 80% R.H. with good air circulation provided a suitable condition for complete fixation of copper in a short period. After the applied post-treatments, up to 11.3% cupric copper reduced to cuprous form. A higher copper conversion rate usually corresponds to lower copper leaching, which is consistent with the contribution of lower water solubility cuprous copper.     

Effects of delayed drying and CO2 application on copper amine fixation in ACQ treated red pine

Fixation of copper and amine in alkaline copper quaternary (ACQ-C) wood preservative was investigated to determine the effects of delayed drying and application of CO₂ gas under pressure. Unlike the fixation of CCA preservative, where the rate of fixation reaction is slowed down by evaporative cooling during drying, delayed drying of ACQ treated wood had no observable effect on the copper fixation rate. However, at 50 °C, delayed drying resulted in a higher degree of copper fixation, while this effect was not observed at 22 °C. Post-treatment of ACQ treated wood with pressurized CO₂ immediately after treatment, reduced the pH of the solution in wood and resulted in rapid fixation of the copper. However, in time, the pH increased as CO₂ dissipated from the solution allowing the copper to re-solubilize.     

Effect of radiata pine juvenile wood on the physical and mechanical properties of oriented strandboard

This work analyzes the impact of radiata pine (Pinus radiata D. Don) juvenile wood on the physical and mechanical properties of oriented strandboards (OSB). Radiata pine logs were obtained from 10 trees of a 26-year old managed stand located in the 8th Region of Chile. The experimental design considered the proportion of juvenile wood and strand orientation as independent variables. OSB panels of 0.4 m×0.4 m×12 mm were produced and tested. The results show that the juvenile wood proportion has a significant impact on the physical and mechanical properties of OSB. Strands orientation had a significant impact on all the properties studied with the exception of the modulus of elasticity in bending. However, this impact was small in all cases and would not change panel grade with the exception of linear expansion. In this case, panels made from tangential strands showed a higher linear expansion. According to these results, radiata pine juvenile wood can be used for the manufacturing of OSB up to a proportion of 70% of the oven-dry wood weight without significant losses of the physical and mechanical properties if the juvenile wood strands are located in the surface layers.     

Chemical investigations on boiling process waters in face veneer production

Boiling processes in veneer industry generate large amounts of process water replete with dissolved wood extractives. In the present study the chemical composition of boiling waters from 18 industrially treated wood species were investigated. Contamination levels of the boiling waters varied within a wide range depending on the different extractive contents of the processed wood species and operational conditions. Boiling wood species with high extractives content, heated over several days at temperatures above 80 °C, generate highly loaded waste waters with chemical oxygen demands (CODs) of up to 7000  mg l^-1. The determination of the elemental composition, using optical emission spectrometry (ICP-OES), showed iron contents of up to 10 mg l^-1. Phenolic compounds were in a range of 40 to 900 mg l^-1. Flavonoid compounds and phenolic acids were identified in the boiling waters by liquid chromatography (RP-HPLC-UV). The results confirm the need for water treatment facilities to establish a recycling process and to avoid discolourations of the wood by accumulated wood extractives.     

Removal of Pb(II) from aqueous solutions by carbons prepared from Sal wood (Shorea robusta)

In the present work, physically and chemically activated carbons are prepared using Sal wood (Shorea robusta) sawdust by thermal process and using sulfuric acid as the activation agent to remove Pb(II) from aqueous solutions. Adsorption equilibrium studies have been done at a pH of 4 and a room temperature of 30 °C. It was found that the adsorption isotherms are favorable and chemically activated carbons are better than physically activated carbon in terms of adsorption capacity. Various two-parameter adsorption isotherm models, viz. Freundlich, Langmuir, Temkin and Dubinin-Radushkevich, were used to fit the equilibrium data and it was found that the Freundlich adsorption model provided best-fit. The first-order irreversible unimolecular reaction model and the pseudo-second-order kinetic models were used to fit the kinetic data and it was found that both the models provided good fit. Kinetic and film diffusion studies show that the adsorption of lead(II) on the activated carbons tested in this work are both intra-particle and film diffusion controlled.     

Prehydrolysis of xylan in culm of Sasa kurilensis with dilute sulphuric acid

To prepare a substrate for microbial conversion of xylose into xylitol, the culm of Sasa kurilensis was hydrolysed with dilute sulphuric acid. A fermentable substrate with a relatively high xylose concentration (21.9?g?L^?1) was obtained by hydrolysis with 2% sulphuric acid with a liquid to solid ratio of 10?:?1 at 121°C for 1?h. During hydrolysis at elevated temperatures, some undesirable byproducts were also generated, such as degradation products of solubilized sugars and lignin, which are potential inhibitors of microbial metabolism. These compounds were successfully removed from the hydrolysate by treatment with a commercially available activated charcoal (30?g?L^?1 dose).     

Comparison of a small and a large environmental test chamber for measuring VOC emissions from OSB made of Scots pine (Pinus sylvestris L.)

An investigation was undertaken to compare small environmental test chambers (23.5 L) with large ones (1 m³) for measuring the release of volatile organic compounds (VOC) from OSB made of Scots pine (Pinus sylvestris L.). Two samples were cut from one industrially manufactured OSB and were tested over a period of 45 days. Emissions are mainly composed of monoterpenes and aldehydes. Only small differences are obvious in the results acquired in both chambers. The maximum deviation of ±10% must be rather subscribed to stochastic and systematic errors of the method than to differences between both chambers. Thus, small environmental test chambers are generally suitable for measuring organic emissions from wood and wood-based products.     

CT-scanning and modelling of the capillary water uptake in aspen, oak and pine

This study utilises Computer Tomography (CT-scanning) to characterize the capillary water uptake in wood specimens. CT-scanning makes it possible to study the capillary rise of water as a function of height in wood specimens after a specific exposure time. The study has also included the development of a theoretical model, which determines the capillary characteristics of wood in relation to its structure. The model developed was tested using experimental results, considering the capillary suction height and the water content change after a specific time as boundary values. A comparison between the theoretical model and the experimental results shows that not all the cells in the wood samples take part in the capillary water transport. It also appears that there is a structural resistance to capillary flow.     

Influence of dipping time on uptake of preservative solution, adsorption, penetration and fixation of copper-ethanolamine based wood preservatives

Copper-ethanolamine based wood preservatives are the most important products for protection of wood in use class III and IV applications. These preservatives can be applied using different procedures. One of them is dipping, a method which is predominantly used in less industrialised countries. The most important parameter, that influences the quality of this treatment, is dipping time. Influence of various dipping times on copper retention, adsorption, penetration, colour of the specimens and copper fixation was examined. In this paper copper-ethanolamine solutions of two different concentrations were utilised (c_Cu=0.05% or 0.25%). The results showed that longer dipping treatments resulted in higher uptakes of preservative solution, better penetrations and lower leaching of copper-ethanolamine based wood preservatives from Norway spruce wood. After one week of dipping, samples retained on average 275 kg/m³ of preservative solution, copper active ingredients penetrated on average 3 mm into the specimens, and only 2.3% of copper was emitted from wood impregnated with aqueous solution of the higher concentration, when subjected to ENV 1250 leaching procedure.     

Eigenschaften von extrudierten Holz-Kunststoff-Werkstoffen auf Basis von Refiner-(TMP-)Fasern und Hanffasern

At present, wood particles (wood flour) with a low aspect ratio are mostly used as fillers in wood-plastic composites (WPC). Reinforcement of WPC and improved strength properties may be achieved by using real wood fibres with a high aspect ratio. WPC based on 70% (wt.) refiner (TMP) wood fibres and mechanically processed hemp fibres were extruded in a two-step process. Eleven compounds based on the two natural fibre types were prepared using a thermokinetic mixer and extruded in a conical, counter-rotating twin-screw extruder. Additional formulation components were polypropylene fibres, maleic anhydride-modified polypropylene (MAPP) and lubricant. It was determined that compounding in a thermokinetic mixer is a useful step for processing of WPC with refiner and hemp fibres as little fibre damage occurred. However, during extrusion, both natural fibre types were severely shortened due to strong shear forces, and homogeneous dispersion of fibres in the matrix was not achieved. WPC based on hemp fibres displayed the best strength properties of the formulations tested. Current extruder screw and die configurations need to be modified to achieve improved fibre reinforcement and to create new, structurally demanding applications for WPC. Using dynamic mechanical analysis, fibre-matrix adhesion of WPC was investigated, and activation energies for glass transition of selected formulations were calculated. Activation energy for formulations containing MAPP was higher than for WPC without MAPP. This indicates that better fibre-matrix adhesion was achieved in formulations with MAPP.     

Ring width, latewood proportion and dry density in stems of Pinus brutia Ten.

This study examined basic characteristics of stem wood produced in Pinus brutia Ten. reforestations in Northeastern Greece. Sixteen dominant trees growing at good and medium site qualities were felled at 14–22 years. Site quality classification was based on site quality surrogates and confirmed by using site index curves that were created for a neighbouring area. Discs were taken at three stem positions (base, middle, top) to study variations in ring width, latewood proportion and dry density. Generally, at both good and medium sites, ring width was found to increase towards the top of the stems while latewood proportion and dry density showed a negative relationship with stem height. Radial variability trends were similar at all heights, and at both sites, revealing a rapid increase for ring width in the first 3–6 annual rings followed by a decrease towards the bark, a gradual increase for latewood proportion and no specific change for dry density. Comparisons between wood material produced during the same growth period (2005–2001) showed statistically significant differences among sampling heights in all cases except for dry density in medium sites. At the base of the stems, mean ring width and dry density were significantly (P?≤0.05) higher at good sites (3.6 mm and 0.53 g/cm³) than at medium sites (3.0 mm and 0.50 g/cm³). However, the differences between the sites are of small magnitude and therefore have limited practical impact on wood processing. The availability of such data is useful in utilising small-dimension timber of brutia pine.     

Use of alkyl ketene dimer (AKD) for surface modification of particleboard chips

The study objective was to impart urea-formaldehyde (UF) bonded particleboards higher and longer-lasting hydrophobicity than that resulting from conventionally used paraffin. Alkyl ketene dimer (AKD) is a paper sizing agent that can theoretically esterify wood compounds and result in a surface modification. Particles were 1) impregnated with an aqueous AKD-solution and cured at 130 °C prior to gluing, or 2) sprayed with a mixture of AKD-solution and UF-resin in a single step. Boards with and without paraffin wax were used as controls. Thickness swelling after 2, 24, and 48 h immersion was decreased by 90, 62, and 59% when the chips were impregnated with AKD in comparison to untreated control boards. Water uptake after 2, 24, and 48 h was reduced by 91, 75, and 60%. AKD-impregnation with subsequent curing decreased the internal bond strength by 53%, indicating that AKD impedes the adhesion. The mixture of AKD and UF-glue did not result in considerable hydrophobicity. Increased methyl/methylene and carbonyl bands in FTIR-spectra after toluene-extraction suggest that AKD partially formed ester bonds at the wood surface.     

A comparative study on brown-rot fungus decay and subterranean termite resistance of thermally-modified and ACQ-C-treated wood

The resistance of thermally-modified and Alkaline Copper Quaternary type C (ACQ-C) treated aspen (Populus tremuloides Michx), jack pine (Pinus banksiana Lamb.), yellow-poplar (Liriodendron tulipifera L.), and Scots pine (Pinus sylvestris L.) against the brown-rot fungus (Gloeophyllum trabeum) and Eastern U.S. subterranean termite (Reticulitermes flavipes) was studied. Wood materials were thermally-modified at a temperature of 210 °C for 15 min. ACQ-C was impregnated into yellow-poplar and jack pine wood at three different retention levels and at each level both leaching and non-leaching procedures were conducted. Results indicate that ACQ-C-treated yellow-poplar and jack pine became significantly more resistant to the brown-rot fungus compared to the thermally-modified wood and the untreated control. Thermally-modified yellow-poplar and jack pine were more resistant to this fungus than untreated wood. For aspen and Scots pine, the resistance to G. trabeum was improved after the thermal modification, but it remained susceptible to this brown-rot fungus decay. Termite susceptibility of thermally-modified aspen, jack pine, and yellow-poplar was comparable to that of untreated controls. Significantly greater termite attack occurred on thermally-modified Scots pine wood than it did on untreated wood. This likely is attributed to some compounds contained in Scots pine wood that inhibited termite attack.     

The efficacy of commercial silicones against blue stain and mould fungi in wood

Scots pine (Pinus sylvestris L.) samples were vacuum pressure impregnated with quaternary ammonium (quat)-silicone micro-emulsion (<40 nm particle size), amino-silicone macro-emulsion (110 nm) and silicone macro-emulsion with alkyl modified side groups (740 nm). Quat-silicone micro-emulsion caused highest cell wall bulking (4.8%) and anti-swelling efficiency (21.8%) in wood when treated with 30% concentration of silicone in the treatment solution. All three formulations made wood hydrophobic which was evident from a capillary (longitudinal, tangential and radial) water uptake test. Amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in strong resistance to blue stain attack with both pre-weathered and not pre-weathered wood samples. Signs of blue staining were more evident on the pre-weathered samples. Treatment with amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in a certain resistance to mould growth on wood surfaces, whereas wood treated with the same concentration of quat-silicone micro-emulsion and alkyl-modified silicone macro-emulsion exhibited comparatively lower resistance.