Your search resulted in 82 documents. Displaying 25 entries per page.
Curing conditions for a low formaldehyde etherificated melamine resin
1998 - IRG/WP 98-40108
Waterbased methanol etherificated melamine formaldehyde resins have the potential to increase the resistance of impregnated wood against wood destroying fungi. Previous studies indicated that the resin with the lowest formaldehyde content tested showed the best results regarding fungal resistance, dimensional stability and formaldehyde emissions after curing. In the present paper the influence of curing-time and curing-temperature of the resin with the lowest formaldehyde content is presented. It is demonstrated, that a sufficient curing of the resin requires temperatures in the range between 120-140°C for a period of several hours. The addition of pure urea leads to reduced formaldehyde emissions while the anti-fungal effect of the resins increases or remains the same.
D Lukowsky, R-D Peek, A O Rapp
In situ testing the influence of melamine resins on the enzymatic activity of basidiomycetes
1999 - IRG/WP 99-30194
Waterbased methanol etherificated melamine formaldehyde resins have the potential to increase the resistance of impregnated wood against wood destroying fungi. The mechanism of the increased wood durability is not clear yet. In the present paper the possible interference of melamine resins with wood degrading enzymes of Coniophora puteana and Trametes versicolor was investigated as a possible contribution to the increased wood durability. An in situ photometric assay was used to measure the enzymatic activity against Walseth cellulose, pine sapwood as well as lignin and xylan preparations.
D Lukowsky, F Büschelberger, O Schmidt
Properties of strand board bonded with ammonium pentaborate (APB) modified phenol formaldehyde resin
2009 - IRG/WP 09-40455
Ammonium pentaborate (APB) is combined with phenol formaldehyde (PF) resin in this study to develop a high-performance wood-based composite. The effect of APB and its combination with polyethylene glycol (PEG) on the physical, mechanical properties as well as formaldehyde emission of strand board were tested and compared with disodium octaborate tetrahydrateand (DOT) and zinc borate (ZB). The results showed that APB has negative effect on the mechanical properties of the strand board, but the distribution of APB only on the surface in the 3-layer strand board can reduce this negative effect significantly. Except only marginal increase on the thickness swelling, PEG displays a positive effect on internal bond strength, modulus of rupture (MOR), and modulus of elasticity (MOE). As expected, APB showed decreasing effect on the formaldehyde emission.
Wei Gao, Jinzhen Cao
Detection of feeding behaviour of termites using AE monitoring
1991 - IRG/WP 1514
Using acoustic emission (AE) monitoring, the feeding activity of the termite inhabiting a wood specimen was investigated. The amplitude and the rate of AE from the specimen of Coptotermes formosanus Shiraki was larger than that of Reticulitermes speratus Kolbe. The AE event rate was higher in the specimen with soldiers than without soldiers. The AE event rate decreased according to the resistance of wood specimens against termite attack.
Y Imamura, M Tokoro, M Owada, Y Fujii, M Noguchi
Modélisation sur maquette du rejet accidentel d'un gaz toxique et inflammable dans l'atmosphere - Emission de type "bouffée d'oxyde d'éthyléne [Water model simulation of toxic and flammable gases in the environment on industrial sites - Puff of ethylen oxide]
1990 - IRG/WP 3576
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
Rates of emission from CCA-treated wood in the marine environment: measurement, modelling and requirements for further research
2001 - IRG/WP 01-50166-12
Accurate estimates of rates of emission of leachate from preservative treated wood are crucial for realistic predictions of the environmental impact of its use in maritime construction. Estimates are available for some commonly used preservatives, but these vary widely. Though variable, these measurements suggest that emission generally decreases exponentially with time. Part of the variation is due to differences in methodology employed. Physical and chemical characteristics of the seawater used (e.g. temperature, salinity, pH and oxygen content) affect emission rate. So too do the specifics of the treatment process especially the preservative formulation used, and pre- and post-treatment handling of the wood. The nature of the treated wood samples is also important, with misleadingly high estimates being obtained from samples with unrepresentatively high proportions of cross-cut surfaces. A suggested strategy for developing an informative and standardised methodology is discussed. To form useful models of impacts of leaching, emission rates need to be considered in conjunction with site-specific information regarding a) water exchange rates between the area where leaching occurs and the sea, and b) the extent of partitioning of leachate between the water column, biota and sediment. The risk of environmental impact may be reduced by modification to treatment procedures and by careful planning of installation.
S M Cragg, C J Brown, R A Albuquerque, R A Eaton
A review of environmental emissions from building and construction materials in comparison with preserved wood
2005 - IRG/WP 05-50224-11
A review of the public domain literature concerning emissions to the environment from materials which are used in the construction of buildings (e.g. Concrete, Asphalt, Galvanised Steel), in comparison with preserved wood, and a review of the approaches taken by the construction sector in assessing the risk from environmental emissions, in comparison with the approaches taken by the wood preservation sector.
E F Baines
Oxygen index levels and thermal analysis of wood treated with melamine-formaldehyde-boron combinations
1997 - IRG/WP 97-30135
Melamine formaldehyde (MF) resin was impregnated into scots pine (Pinus sylvestris L.) specimens with aqueous solutions of 5, 10 and 20% concs. Boric acid (BA) and borax (BX) was added to MF resin at the concentration levels of 0.25, 1.00 and 4.70% to each level of resin concs. BA and BX mixture was prepared at the 5:1 (w/w) ratio considering resultant pH of solutions and better fire resistance. Untreated and treated wood with all combinations were subjected to oxygen index test according to ASTM D 2863-91 and thermal analysis. Results were evaluated in terms of improvement of fire retarding performances of wood by sole or combination treatments.
M K Yalinkilic, W-Y Su, Z Demirci, E Baysal, M Takahashi, S Ishihara
Combined effects of the treatment of wood with formaldehyde
1978 - IRG/WP 3117
Treatment of fibrous materials with reagents in a vapor phase is neither new nor unique. Numerous examples exist in literature of vapor phase experiments on cellulose fibers and fabrics, and on wood. For many years the textile research and industry have used vapor phase processes for the treatment of textiles. The chemical modification of cellulose is based on different types of reactions e.g. esterification, alkylation, resin formation or polymerization, monomer grafting and crosslinking. Vapor phase treatment of wood offers certain potential advantages over the conventional liquid phase wood impregnation. The higher mobility of low molecular weight compounds in the gaseous state ensures a rapid, uniform and homogeneous distribution throughout the wood structure. The vapor phase treatment of wood is also a better approach from the standpoint of cell wall penetration. Bulking, which takes place in the cell wall only, means that less chemicals are required and that the final weight of the composite is limited. Furthermore, due to the low viscosity of a gas, the application of a lower pressure differential remains possible. Within the framework of a wood improvement programme carried out at the Laboratory of Wood Biology and Wood Technology (University of Ghent, Belgium) the treatments were based on the impregnation of wood with liquid synthetic monomers and with gaseous formaldehyde. The results of the hygroscopic and dimensional behaviour of the wood-plastic-combinations have been published previously. Other papers deal with the physical and chemical interactions between the synthetic products and the natural polymers of the cell wall. This contribution will be restricted to the treatment of wood with formaldehyde in the gaseous state.
M Stevens, J Schalck
Methane emission by termites, Coptotermes formosanus Shiraki
1995 - IRG/WP 95-10099
Association of methanogenic bacteria only with the smallest-sized symbiotic protozoa Spirotrichonympha leidyi Koidzumi was evidenced by epifluorescence microscopic observations. Workers, which were collected from a laboratory colony and placed in a test container with water supply emitted methane at a relatively constant rate with a peak of 0.76 nmol/termite/hr within the first 72 hrs after the initiation of measurement. Soldiers, as expected, produced less methane with a maximum rate of 0.019 nmol/termite/hr. Although methane formation is considered important to termites in order to keep physiological balance, that undesirably contributes to global warming.
K Tsunoda, W Ohmura, M Tokoro, T Yoshimura
How to determine what is a realistic emission from treated wood - basic reflections
1998 - IRG/WP 98-50105
Emissions from treated wood occur by evaporation and by leaching. Up to date by far more experience exists on leaching tests than on evaporation test. The methods applied will be of interest to give answers to the questions about the quantity of possible emissions. Standardisation on leaching started very early. One of the first attempts to quantify the effect of leaching on the remaining efficacy was the German DIN 52176-2 (1941) which was the basis for EN 84 first published by CEN in 1978. A specific German standard for the determination of leachates was published in 1972 (DIN 52172-2), however, the viewpoint was still the efficacy of wood preservatives. With respect to pollution of the environment EN 1250-2 (1995) has to be mentioned, however, this is more or less only a modification of EN 84 and as such not very satisfactory. Evaporation tests started as late as in the 50th mainly in connection with fluorides and later with PCP. Examples for a standard to determine the remaining efficacy are the German Pre-Standard DIN 52172-3 (1971) and EN 73, based on the German standard and first published in 1978. A specific standard for emissions is EN 1250-1 (1995). The reflections presented in the paper consider evaporation as well as leaching tests where the general requirements and the statements to the kind of specimens and to the treatment apply to both types of emissions at the same time. For the test procedure itself, however, different methods are needed.
H Willeitner, R-D Peek
Measurement of VOC emissions from curative treated wood: A new emission test chamber
2001 - IRG/WP 01-50166-13
A poor indoor air quality (IAQ) is now recognized as a potential factor affecting occupants health. There are three basic strategies to improve IAQ: source control, improvement of the ventilation and use of air cleaners. Usually, the most efficient way to improve IAQ is to eliminate the different pollutant sources or to reduce their emissions. In order to precisely measure emissions from building products and estimate the potential heath impact of emitted pollutants, standardised analytical methods are needed. The aim of this paper is to present the new standards prepared by the European Committee for Standardization (CEN) and the International Organization for Standardization (ISO) for the measurement of indoor air pollutants and their application to the characterization of emissions from wood products. The prestandard ENV 13419, subdivided in three parts, has been prepared by the CEN technical committee 264 : ??ENV 13419-1 : Building products - Determination of the emission of volatile organic compounds - Part 1 : Emission test chamber method, ??ENV 13419-2 : Building products - Determination of the emission of volatile organic compounds - Part 2 : Emission test cell method, ??ENV 13419-3 : Building products - Determination of the emission of volatile organic compounds - Part 3 : Procedure for sampling, storage of samples and preparation of test specimens. The two first parts of the prestandard ENV 13419 specify a general laboratory test method for the determination of the area specific emission rate of volatile organic compounds (VOCs) from newly produced building products under defined climate conditions in a test chamber (Part 1) or cell (Part 2). The third part specifies for solid, liquid or combined products, the sampling procedure, transport and storage conditions and preparation of test specimens. In France, those European prestandards have been translated by the French Normalisation Association (AFNOR) in three experimental standards : XP ENV 13419-1, XP ENV 13419-2 and XP ENV 13419-3 [1-3]. In parallel to the ongoing work at CEN, the technical committee 146 of International Organization for Standardization (ISO) has prepared the draft international standard ISO/DIS 16000 related to indoor air. Part 6 of this standard specifies a method for the determination of the emission of single volatile organic compounds (VOCs) and total volatile organic compounds (TVOC) from building materials using test chambers and cells : ??ISO/DIS 16000-6 : Indoor air - Part 6 : Determination of volatile organic compounds in indoor and chamber air by active sampling on TENAX TA sorbent, thermal desorption and gas chromatography using MS/FID. It is intended that, after the final voting stage, the CEN prestandards (Parts 1-3) will be taken over by ISO and that Part 6 of the ISO standard will be taken over by CEN as the fourth part of the ENV 13419 prestandard. As an example, the volatile organic compounds emissions from preservative treated wood samples were characterised according to the CEN ENV 13419-1 prestandard describing the emission test chamber method and to the ISO/DIS 16000-6 prestandard for the analytical method. Two representative wood preservatives (hydrodispersable and petroleum solvent formulation) were tested for this purpose. The VOCs concentrations in the test chamber were monitored during 6 days following a simulated curative wood treatment.
F Maupetit, O Ramalho, C Yrieix
Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic conditions. Part 2: Semi-industrial investigation
1995 - IRG/WP 95-50040-13
In continuation of previous leaching research on the quantification and modelling of metal elements released from CCA treated timber, a series of experiments has been carried out dealing with the influence of temperature and pH of the relative aquatic environment. The leaching method used is the Dutch prestandard for building materials, a long term static leaching test simulating practical bank-shoring situations. Parameters of study are type of fixation, wood species and specimen profiles. With decreasing water temperature, significantly less leaching of copper, chromium and arsenic is observed. An outdoors/indoors temperature ratio of 0.7 could be established. Increasing acidity of the leaching water mainly enhances the release of copper, whereas chromium and arsenic show a minimum leaching tendency at neutral pH. Both conditioning chamber fixation and steam fixation prove to be effective in fixing the metal elements in the wood substrate. With steam fixed timber, however, a higher loss of copper is observed during the early leaching cycles, due to the presence of copper salts on the wood surface. With regard to specimen profiles, boards in comparison with posts demonstrate a remarkable resistance to leaching of active ingredients, presumably due to the different heartwood/sapwood distribution and the specimen dimensions. In conclusion, the observations made confirm the results obtained from previous leaching studies. Converting the emission data into leaching fluxes, a highly correlated double logarithmic flux formula is regarded the best tool for curve fitting, however, for a limited time span. Other models which are more suitable for extrapolation of emitted quantities over a longer period of time are still under investigation. Likewise, proprotional metal ratios versus retention levels highlight the relativity of experimental data obtained with standard emission tests.
G M F Van Eetvelde, W J Homan, H Militz, M Stevens
Emission of trimethyl borate and methanol from radiata pine (Pinus radiata D. Don)
1995 - IRG/WP 95-30088
Sawn and kiln dried radiata pine conditioned to 3, 6, and 12% moisture content was treated with trimethyl borate (TMB). The treated wood samples were placed in mini-desiccators maintained at 20 or 40°C. The air space within the mini-desiccator was analysed for TMB and methanol. An initial period of emission of TMB and methanol was observed. This was followed by a period of gradual dissipation of both TMB and alcohol. There was an equilibrium of 2 ppm and 60 ppm respectively of TMB and methanol for 12% moisture content timber stored at 20°C. Dissipation was slower for 6% and 3% moisture content timber. Higher temperatures resulted in higher concentrations of TMB and methanol during the emission and dissipation stage.
F J Romero, P Vinden, J A Drysdale
Thermotolerant mould growth in dehumidifier kilns in New Zealand
1996 - IRG/WP 96-10169
Growth of Aspergillus fumigatus and Paecilomyces variottii is common on wood dried in dehumidifier kilns that operate within a temperature range of 35-55°C. Aspergillus fumigatus causes an unacceptable blue / grey discolouration of the woods surface and prolonged exposure to spores during handling of mouldy wood can cause health problems amongst timber workers. A survey of dehumidifier kiln operators in New Zealand was carried out to ascertain the extent of the problem and investigate control options. Significant growth only occurred if initial wood moisture content was above 80%. Results suggested that this was because high relative humidity (98-100%), for periods in excess of 5 days, was a requirement for extensive and profuse growth to occur. Only 3 of the 26 antisapstain treatments tested using a 3 week laboratory trial gave control of Aspergillus fumigatus at 40°C. Fumigation with 4 ppm (mg/litre of air) of formaldehyde gas controlled growth of Aspergillus fumigatus for periods up to 5 days and a second fumigation was often needed for long drying cycles (> 12 days). It seems likely that growth of thermotolerant moulds became a problem when use of pentachlorophenate as an antisapstain treatment was phased out (1988-89). Laboratory trials showed that this was one of the few fungicides that controlled Aspergillus fumigatus.
R N Wakeling, J G Van der Waals
Feasibility of termite control using crushed cement-stabilized sludge (Polynite) as a physical barrier and acoustic emission (AE) monitoring
2000 - IRG/WP 00-10381
In Japan, the damages by the subterranean termites (Coptotermes formosanus Shiraki and Reticulitermes speratus Kolbe) are more common. Recently, the more attention is paid to the methods of the termite controls of less- or non-chemical. As one of the non- chemical treatment, physical barrier using particles as basalts 1) , granites, and gravels 2) were investigated in terms of its safety, cost effectiveness and duration of performance, and there were also examples that the physical barriers using some particles have been put to practical use in a few countries except in Japan. Ebeling and Pence showed that the relationship between particle size and termite body size is an important factor in controlling tunneling activity of subterranean termites, and the crushed volcanic cinders of 0.85-2.36 mm in diameter prevented R. hesperus from penetrating 3) . Tamashiro and co- workers indicated that the particles of particular sizes (1.70-2.40 mm in diameter) prevented C. formosanus from penetrating 4) . Su and co- workers investigated the penetration of the sand barrier consisting of crushed quartz rocks and fossilized coral by C. formosanus in laboratory- and field-testing 5, 6) . These results show that it is important to investigate the relationships between the size of termites and particles to evaluate the effects of the physical barrier using particles. On the other hand, in Japan surplus soils and sludge of sixty million tons per annum are discharged from construction sites. The recycle techniques using the surplus soils and sludge and the development of the market for these recycled products are the theme of importance. The crushed cement- stabilized sludge (Polynite) as one of the recycled products of surplus soils and sludge is one of the newly developed and recycled material. It is technically suitable for mass production, has grate cost effectiveness, and is easy to uniform the particle size. In this study, the feasibility of a physical barrier using Polynite uniformed the particle size for termite was examined in a laboratory testing. AE monitoring 7-13) as a method forthe detection of the penetration of termites into the Polynite barrier at an early stage was also investigated, for the application of Polynite barrier in the house.
Y Yanase, M Shibata, Y Fujii, S Okumura, K Iwamoto, T Nogiwa, T Yoshimura, Y Imamura
Feasibility of AE (Acoustic Emission) monitoring for the detection of the activities of wood-destroying insects
1992 - IRG/WP 92-2416
The feasibility of acoustic emission (AE) as a nondestructive testing method for the detection of the wood destroying insects was investigated. AEs were detected from the wood specimens under feeding attack of sugi bark borers or powder-post beetles. However, the feasible monitoring area of an AE sensor is influenced by the attenuation of AE amplitude, so that this could be a problem in the practical AE measurements, especially with wood specimens of higher moisture content.
Y Fujii, Y Imamura, E Shibata, M Noguchi
Effects of a formaldehyde and sulphur dioxide treatment on decay and mechanical properties of aspen waferboard
1983 - IRG/WP 3242
Aspen wafers were sequentially treated under vacuum with formaldehyde and sulfur dioxide gas and pressed into waferboard bonded with powdered phenol formaldehyde resin. Decay resistance and strength properties were determined before and after simulated weathering. The water resistance of the phenol bonding system was lost in board made from the gas-treated wafers. This white rot fungus Coriolus versicolor was unable to decay treated waferboard in a soil block test, but the brown rot fungi Gloeophyllum trabeum and Poria placenta decayed the samples as severely as untreated controls.
E L Schmidt
Detection of Acoustic Emission (AE) generated by termite attack in a wooden house
1999 - IRG/WP 99-20166
Recently, considerable attention has been paid to methods for termite control, which involves few or no chemicals. To reduce the amount of termiticide needed, it is necessary to detect termite attack in wood as early as possible. The feasibility of acoustic emission (AE) monitoring for the nondestructive detection of termite attack has been discussed previously. In this study, we propose some technical solution for the application of AE monitoring to practical control operations. Using a needle-type waveguide combined with an AE sensor (PZT sensor), AEs generated and propagated within floors and walls could be detected effectively. A 0.04 mm-thick sample of the piezoelectric polymer PVDF, which was inserted between the construction members of wooden houses, could detect Aes propagated both in such members and at joint surfaces, although PVDF film is less sensitive than a PZT sensor. The feasibility of using a portable AE detector as the input device for a total security system against termite attack in a house is also discussed.
Y Fujii, Y Yanase, T Yoshimura, Y Imamura, S Okumura, M Kozaki
Detection of termite attack in wood using AE monitoring
1990 - IRG/WP 2355
An acoustic emission (AE) monitoring method for detecting termite activity in wood was applied to lumber of 3 by 3 cm to 10 by 10 cm square, 1 m long. Furthermore, the propagation of AEs due to the feeding activities of termites in the specimens and the locations of AE sources were analyzed. Also discussed was the feasibility of the method applied to posts out in the field of subterranean termites. The results obtained from laboratory and field tests suggest that AE monitoring could be an effective non-destructive method to detect feeding activity of termites even in the incipient stages of the termite attack in wood.
Y Fujii, M Owada, M Noguchi, Y Imamura, M Tokoro
Durability of surface preserved wood particle boards submitted to atmospherical influence
1995 - IRG/WP 95-40039
The worldwide problem of the continuously growing deficit of high quality natural wood material has caused the attempts of many research workers to find effective composites such as wood particle boards (WPBs) for replacing the massive wood for constructive purposes, depending on where the boards are exploited - in the open or under a shed, they are submitted to various climatic factors such as heating, drying, moistening, frosting, irradiation, that's why for reaching high atmospheric resistance, it is very important, a durable protection of the WPBs with suitable coatings against the atmospheric influence to be ensured.
Treatment of wood with formaldehyde. Acid catalysis of the reaction between formaldehyde and wood
1980 - IRG/WP 3146
Formaldehyde reacts with the free OH-groups in wood forming cross-linking bonds. The reaction can be brought about without any catalyst but in that case the activation energy is very high and high temperatures and long reaction times are needed. Normally, the reaction is catalysed by different acids. Acid catalysts, however, tend to degrade the cellulose and the wood matrix causing reduction in the strength of the wood. The effect of the specific properties of catalysts on the cross-linking and hydrolytic reactions as well as the reaction kinetics have been inadequately investigated. Investigations on the treatment of wood with formaldehyde were started in 1976 at the Forest Products Laboratory of the Technical Research Centre of Finland. In the beginning, HCl-catalysed treatments were used which proved to reduce the strength properties of wood rather strongly. In continued trials more satisfactory catalysts have been sought in order to achieve maximal formaldehyde cross-linking and minimal degradation of the wood. The tests have included various inorganic and organic acids and metal halides soluble in water as well as sulphur dioxide (SO2) and boron trifluoride (BF3) in vapour phase. Some of the results are reviewed in this paper.
T Vihavainen, K Piispanen, P Mansikkamäki
A Long-term Observation of Termite Activity in The Nest by Continuous Acoustic Emission (AE) Monitoring
2003 - IRG/WP 03-20280
In order to evaluate the influence of temperature on the termite activity, acoustic emission (AE) monitoring was applied to two nests of Coptotermes formosanus SHIRAKI; a nest in the stem of a standing tree and a nest in the underground of a wooden house, respectively. Temperature change in and around the nests were continuously measured for about one year using thermocouples at four points; the centre of the nest, the periphery of the nest, the environment around the nest, and the underground, respectively. AEs were detected at the centre of nest and underneath the nest sphere by using wave-guides inserted into the nest of the standing tree and at the centre of nest. AEs were also detected at the wooden construction member near the nest in the wooden house. The termites in the nests were periodically stimulated by rotating, drawing and sticking the wave-guides. The temperatures in the both nests varied from 5 to 35 °C during the experiment. The highest and the lowest temperatures were recorded in August and February, respectively. The highest AEs event rate was recorded when the temperature of the nest in the tree was between 30 and 35 °C and when the temperature of the nest under the house was above 25 °C. In winter, when the nest temperature was below 10 °C, no significant numbers of AE were detected. These findings clearly show that AE generation has a close relation to the termite activities, which are influenced by the temperature in the nest.
Y Yanase, Y Fujii, S Okumura, T Yoshimura, Y Imamura
Microscopical analysis of formaldehyde-acid modified wood
1981 - IRG/WP 3182
Cross-linking of wood with gaseous formaldehyde improves its hygroscopic and dimensional behaviour, and its resistance against micro-organisms. However, formaldehyde cross-linking reactions take place only in the presence of an acid catalyst, which results in losses in mechanical By optimization of a formaldehyde-sulfur dioxide vapour phase process the reaction conditions were established to limit losses in modulus of elasticity and bending strength to a few percent. Under these circumstances, impact strength losses of about 50 to 75% were still noted. The reaction of formaldehyde with cellulose has been studied intensively in textile research. However little is known on the fundamental aspects of the interaction of formaldehyde with lignin and wood. In order to get further insight into the effects of a formaldehyde-acid catalyzed reaction on the technological properties of wood a fundamental analysis of the interactions of both compounds with wood has been carried out.
M Stevens, N Parameswaran