Your search resulted in 30 documents. Displaying 25 entries per page.
Rapid loss of lignin at wood surfaces during natural weathering
1992 - IRG/WP 92-2390
Thin veneers of radiata pine (Pinus radiata D. Don) were exposed to natural weathering over a period of 30 days. Incident UV radiation was monitored at the test site. FTIR internal reflectance spectroscopy was used to study the chemical changes taking place at the veneer surface during weathering. Spectra obtained show that after only 3 days exposure there was substantial delignification at veneer surfaces. Large losses in the acid insoluble lignin content of veneers also occurred during weathering. Losses in the wet finite span tensile strength of veneers were more rapid than losses in dry zero span tensile strength. Since delignification reduces wet finite span tensile strength, but has little effect on dry zero span tensile strength, the results here again indicate that lignin loss at wood surfaces during exterior exposure is surprisingly rapid. Changes in the morphology of transverse surfaces exposed to the weather were also largely confined to the lignin rich middle lamella layers. A stepwise loss in weight of exposed veneers after rainfall supports suggestions made in the literature that lignin degradation products are leached from weathered wood by rain.
P D Evans, K J Schmalzl, A J Michell
Detection of incipient brown rot decay in wood by fourier transform infrared spectrometry
1987 - IRG/WP 2275
Fourier transform infrared spectrometry was evaluated as a possible method for detecting different levels of brown-rot decay in pine sapwood. By using first derivative spectra and regression analysis, an equation based on 4 absorption peaks, normalized with an internal standard peak, was developed. The correlation between weight loss and absorption was highly significant indicating that this is a valid method for detecting incipient brown-rot decay.
D D Nicholas, T Schultz
Photo-discoloration and Degradation of Wood and its Stabilisation by Modification with Benzoyl Chloride
2004 - IRG/WP 04-40274
Photo degradation of Pinus roxburghii (chir pine) and Hevea brasiliensis (rubber wood) was studied under artificial accelerated weathering conditions in a Xenon test chamber. The irradiated samples were analyzed for color changes and chemical changes. Analysis of colour changes in wood surfaces by UV-Vis. irradiation was carried out using a colour measuring (CIELAB) system and chemical changes were monitored using FTIR and fluorescence spectroscopy. Irradiation modified physical and chemical characteristics of wood surfaces and resulted in rapid colour changes, reduction in lignin content and increased concentration of chromophoric groups on the wood surfaces. Colour changes were correlated with formation of carbonyl groups and lignin decay rate determined by FTIR measurements. Fluorescence emission spectra measured from un-weathered wood shows excitation wavelength dependence. Photo irradiation leads to a rapid reduction in the emission intensity, broadening of spectra and a significant red shift in the emission maximum. Photo stability of wood surfaces esterified with benzoyl chloride was also assessed. The modification was characterized and analyzed by fluorescence and FTIR spectroscopy and photo-stability of modified wood was assessed. Esterification of wood by benzoyl chloride suppressed the colour changes (photo-discoloration) and also reduced the lignin degradation and generation of carbonyl groups on irradiated wood surfaces. Results show esterification of wood with benzoyl chloride was effective at inhibiting photo-degradation of wood polymers.
K K Pandey
Correlation between changes in colour and chemical composition during photo-degradation of wood surfaces
2005 - IRG/WP 05-40301
Changes in colour of wood (yellowing) during photo degradation or weathering reflect chemical changes in wood. Therefore, the relationship between changes in chemical composition and CIELAB colour parameters is very important to characterize photodegradation of lignocellulosic surfaces. In this study, the changes in chemical composition and yellowing due to photo-degradation was studied by exposing wood surfaces of Pinus roxburghii (chir pine) to a xenon source. Changes in chemical composition were monitored by measuring IR and fluorescence spectra and were correlated with colour changes. A linear correlation between degradation of lignin and total colour change (E) was observed.
K K Pandey
The influence of copper (II) chemicals on the weathering of treated wood. Part 1: ACQ treatment of wood on its weathering
1994 - IRG/WP 94-30040
Wood weathering can be accelerated by alkylammonium compound (AAC) treatment, and slowed by ammoniacal copper quat (ACQ) treatment. This study aims at investigating the influence of ACQ treatment of wood, especially the present of copper (II), on its weathering. ACQ, CCA and DDAC treated microtomed sections of southern yellow pine earlywood were prepared and naturally weathered for five periods, totally 35 days. The compositional changes in the weathered samples with preservatives, retention and exposure time were examined using FTIR spectroscopy. The FTIR spectra showed that ACQ treatment slowed wood photodegradation mainly via inhibiting the formation of carbonyls and delignification during weathering. 2% ACQ treatment provided effective protection against wood photo-oxidation.
Ruiying Liu, J N R Ruddick, L Jin
Analysis of water repellents in wood treated with water borne formulations using FTIR
2000 - IRG/WP 00-40176
The use of aqueous water repellent emulsion formulations has increased significantly in the wood treatment industry. These products are primarily used to enhance the weathering characteristics of wood products treated with water borne preservatives systems used in exterior above ground applications. They are also used in pole treatments to improve climbing characteristics and in low VOC millwork treatments. With the increasing usage of such products. there has been a need to develop analytical methods for the determination of the water repellent in treated wood products to ensure product quality and to aid in the development of enhanced water repellent formulations. A method for the determination of the water repellent concentration in wood was developed using Fourier transform infrared spectroscopy (FTIR). The wood samples were extracted and prepared for the FTIR scans using a liquid cell. The water repellent concentration was determined by using the intensity of the hydrocarbon C-H stretch adsorption. Methods for correcting or eliminating the interference from non-water repellent components in the wood extracts were developed.
P J Walcheski, L Jin
Weathering of copper-amine treated wood
2000 - IRG/WP 00-40155
Copper ethanolamine (Cu-EA) treated southern pine (SP) were artificially weathered with a QUV Weathering Tester. The weathering regime was composed of a continuous UV-light irradiation for 2 hours followed by a water spray for 18 minutes for a total time of 1200 hours. The changes on the surface of the weathered samples were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, color and contact angle measurements. FTIR indicates that Cu-EA treatment can retard the surface degradation during weathering. The reduction of the peak intensity at 1510 cm-1, characteristic of the wood lignin was less pronounced for Cu-Ea treated wood than for untreated or ethanolamine treated wood. This reduction in 1510 cm-1 intensity decreases with the increase of copper EA retention in treated wood. The color change expressed by the value of DE indicated that untreated and Cu-EA treated wood change color rapidly during the first 200 hours irradiation and the color change remained relatively constant thereafter. The values of DE for untreated and ethanolamine treated sample were higher than the values of Cu-Ea treated. Changes in the lightness of wood samples were also observed with the duration of irradiation. The lightness of untreated and Cu-MEA treated samples decreased during the first 100-hour weathering. These samples regained their lightness after 100 hours irradiation. For samples treated with copper concentration above 0.25%, the change in lightness was rather small. The contact angle measurement indicates that the wettability of wood surface increases with the duration of QUV exposure. Untreated and MEA treated wood samples changed contact angles rapidly, and The contact angle of untreated and ethanol amine treated samples dropped from about 75"5 degree to zero after 600 hours artificial weathering. Treatment with Cu-MEA can slow the decreasing in contact angle. After 1200 hours, the contact angle of Cu-EA treated wood dropped from 100 to a minimum between 25 and 60 degree. As the copper concentration increases, the rate of changing contact angle decreases. This study suggests that a copper amine treatment increases the hydrophobic and the resitance to photodegradation.
J Zhang, D P Kamdem
Surface characteristics of wood treated with various AAC, ACQ and CCA formulations after weathering
1991 - IRG/WP 2369
Wood samples treated with various alkylammonium compounds (AACs) as well as ammoniacal copper quat (ACQ) and chromated copper arsenate (CCA) have been studied in accelerated weathering experiments. Microscopic examination of the surfaces of these samples after exposure in a weatherometer revealed several different changes. Samples treated with didecyldimethyl ammonium chloride (DDAC) show considerable latewood defibration and severe earlywood erosion, while ACQ and CCA treated samples are far less prone to surface weathering than AAC treatments as well as the untreated controls. FTIR spectral data of surface material removed from these samples correlated well with the observed surface defibration. It appears that lignin components are most affected by the weathering process. The AAC counterion and chain length of dialkyl quaternaries in AAC treatments appear to influence the weathering effect.
L Jin, K J Archer, A F Preston
FTIR characterization of copper ethanolamine - wood interaction
1999 - IRG/WP 99-20154
The interaction of copper ethanolamine (Cu-EA) and wood components was studied by using Fourier transform infrared spectroscopy (FTIR). In Cu-EA treated wood, significant reduction was noticed on the band attributed to carbonyl vibration from carboxylic groups at 1735±5 cm-1 and an increase in band intensity was obtained from carbonyl in carboxylate at 1595±5 cm-1. The same observation was made in Cu-EA treated holocellulose. Cu-EA treated lignin resulted in a reduction in the aromatic ester band at 1710±5 cm-1 and an increase in carbonyl from carboxylate at 1595±5 cm-1. Bands at 1370 cm-1 and 1221 cm-1 assigned to phenolic hydroxyl groups, exhibited a decrease in intensity after the treatment. From these data, it is concluded that Cu-EA interact with carboxylic groups, phenolic hydroxyl groups and ester groups from lignin to form copper carboxylate and phenolate complexes.
Jun Zhang, D P Kamdem
A spectroscopic investigation of copper ethylenediamine fixation in wood
1999 - IRG/WP 99-20160
The fixation reaction which take place between copper ethylenediamine (Cu-en) solution and wood were expolored using X-ray photoelectron spectroscopy (XPS) and Fourier Transformed Infrared Spectroscopy (FTIR). The FTIR spectra revealed that copper reacts with the carboxylic acid and phenolic groups in wood to form stable complexes. The copper ethylenediamine complexes formed in wood were identified by comparing their XPS spectral parameters with those of similar compounds of known structure. The magnitude of the copper (2p3/2) binding energy of 934.64 eV is lower than that for copper(en)2 sulphate or copper acetate, suggesting that the copper is bonding to less reactive oxygen atoms in wood. This would support a principal reaction between copper and guaiacyl groups in lignin, similar to that suggested for copper-ammonia wood preservatives. The XPS spectra confirmed the ready reduction of the copper(II) in copper-amine treated wood during acquisition of the spectra. However, there was no evidence to suggest that this was occurring during fixation of the copper-amine chemicals. Further studies will explore competing reactions between copper and the wood components to form copper wood complexes with or without amine ligands present.
Xiao Jiang, J N R Ruddick
FTIR studies on the weathering of didecyldimethylammonium compound (DDAC) treated wood
1993 - IRG/WP 93-30013
Wood treated with alkylammonium compounds (AACs), such as DDAC, weathered more rapidly than untreated wood. In order to examine the influence of DDAC treatment of wood on its weathering, treated and untreated microtomed sections of southern yellow pine earlywood of various thicknesses, were prepared and weathered for approximately one month. The changes in these samples were monitored using FTIR. The spectra of DDAC-treated samples showed that the treatment caused the lignin band at 1510 cm-1 to split and decrease in intensity due to chemical interaction between the preservative and lignin. FTIR spectra of the weathered samples confirmed that the removal of lignin and formation of carbonyl groups were greater for DDAC treated samples than untreated controls.
R Liu, J N R Ruddick
A comparison of analytical and visual techniques used for assessment of weathering properties of chromium and copper azole treated timber
1994 - IRG/WP 94-20023
The weathering properties of preservative treated timber were studied by measuring surface lignin loss and by microscopic examination after weathering, and results were related to qualitative assessments of visual appearance after weathering. Measurement of relative rates of delignification of untreated and preservative treated timber obtained by FTIR analysis, and weight loss determined on thin veneers, correlates well with visual assessments of comparative rates of weathering on solid timber exposed to natural weathering in service. Copper Azole treated timber and timber treated with chromium based preservatives showed good resistance to weathering.
J A Cornfield, M D C Hale, G Fettis
Correlation between modulus of elasticity, mass losses and FTIR spectra of copper treated decayed wood
2006 - IRG/WP 06-10580
The composition of copper-based preservatives will change from copper-chromium to copper-ethanolamine, due to environmental demands. The most important drawback of copper-impregnated wood is the presence of tolerant fungal organisms that have developed an ability to degrade such preserved wood. In order to elucidate these processes, specimens (0.5×1.0×15 cm) made of Norway spruce (Picea abies) were vacuum-impregnated with copper-, chromium-, and copper-ethanolamine-based aqueous solutions (cCu=0.5%), and afterwards exposed to copper-sensitive Gloeophyllum trabeum and copper-tolerant Antrodia vaillantii for various times, between one and eight weeks. After incubation, specimens were isolated, and modulus of elasticity (MOE) losses determined using a nondestructive technique. Mass losses, FTIR spectra, and color changes were measured as well. The results showed that there is significant difference between brown rot decay caused by G. trabeum and A. vaillantii. Decay caused by A. vaillantii is more selective than that caused by G. trabeum. Additionally, it was proven that copper effectively protected spruce from G. trabeum, but not completely against A. vaillantii. Decay of copper-impregnated wood by copper-tolerant fungi is similar to decay of control, unimpregnated wood. Whereas decay of copper-impregnated specimens by G. trabeum, was effectively stopped in its initial stage.
M Humar, B Bucar, F Pohleven
Influence of ring width and wood density on durability of oak heartwood
2008 - IRG/WP 08-10639
Oak (Quercus sp.) is considered as one of the most durable European wood species. The most important factor influencing oak durability was extractive content. In our work, we were interested in if oak-wood durability is affected by ring-width and related density. Therefore, oak heartwood specimens made of boards with different ring widths were exposed to five different fungal species Daedelea quercina, Antrodia vaillantii, Hypoxylon fragiforme, Stereum hirsutum and Trametes versicolor according to the EN 113 procedure. In parallel, extractives and nitrogen content were determined as well. From the gravimetrically determined mass losses, and microscopical analysis of decayed specimens, it can be resolved, that oak heartwood specimens with the narrowest growth rings and consequently lower density, were more susceptible to fungal decay than denser specimens made of wider growth rings. Durability of oak heartwood with rings of 0.77 mm and density around 550 kg/m3, is comparable to durability of common beech.
M Humar, P Oven, F Pohleven
Assessment of mould growth on coated wood - methods and application
2009 - IRG/WP 09-20423
Discolouring fungi reduce the service life of coated wooden claddings in façades and increase the total cost of ownership due to shorter maintenance intervals. The project “Enhanced service life on coated wooden facades” has as its main objective to develop new methods for early prediction of durability and longer aesthetic service life of coated wooden cladding related to consumer needs and new building and environmental regulations. Different methods for mould growth assessment on the surface of coated wood exposed outdoors will be looked in to and Quantitative Real-Time Polymerase Chain Reaction (QRT-PCR) and Fourier Transform Infrared Spectroscopy (FTIR) will be developed as tools for objective quantification. In this paper four methods for assessment of mould growth on the surface of coated wood are presented; visual assessment, digital image analysis, QRT-PCR and FTIR, and the application of the different methods are discussed. Further, a comparative study was done using visual assessment and digital image analysis when measuring mould growth coverage on coated wood. 7 coatings with different typology and fungicide were tested according to EN927-3 outdoors for 2 years at Sogn test station, Oslo, Norway. Results obtained from visual assessment by using the rating scale in EN927-3 and a chosen algorithm for digital image processing was compared and the methods showed conformity. Alkyd modified acrylic coatings were found to perform significantly better than pure acrylic and modified alkyd coatings.
L Ross Gobakken, C M Whist, O Høibø, P J Hovde, E Larnøy
Vacuum drying of European oakwood: Color, chemistry and anti-oxidant potency of wood. Improving appearance in forest value added products
2008 - IRG/WP 08-40432
In hardwoods used for decorative and appearance purposes, wood colour is one of the most important factors of wood quality; in addition colour is related with durability and biological decay of wood. Wood discolouration during drying is mainly affected by heat, light, physiological reactions, combinations of reactions, biochemical and chemical reactions, and micro-organisms attack. In freshly felled and stored round wood discolorations are initiated predominantly through physiological reactions of living parenchyma cells. Discolouration during kiln-drying decreases the commercial value of hardwoods, since hardwoods are used in the manufacture of furniture and cabinets. On one hand, heat modifies the cell wall components and induces chemical reactions of nutrients and extractives, by other hand the role of oxygen in kiln dryers is very important due to oxidation reaction of phenolic compounds. The formation of coloured substances from a phenolic compound oxidized with air and the formation of dark materials from hydrolysable extractives are considered causes of discolouration. In order to reduce oxidation reaction, vacuum drying process can be used. In addition, it offers reduced drying times and higher end-product quality in comparison with conventional drying operations. Operating at low pressures reduces the boiling temperature point of water and enables an important overpressure inside the material which is advantageous for drying and especially for species that do not support a high temperature level. In this work, experimental results for the vacuum drying of oakwood with conductive heating are presented for different drying conditions. In particular, surface-wood scans, antioxidant capacity of wood, Fourier Transform Infrared Spectra of dust-wood for different vacuum and convective drying conditions. Sample temperatures and pressure in the dryer are logged during drying. The experimental setup (Figure 1) is a vacuum chamber where pressure is regulated between two values (Pmin, Pmax). The chamber is built in glass; one balance is kept inside the chamber in order to log the mass variation of the sample. A thermometer gives the dryer temperature. The heating source is an electrical resistance which temperature is controlled with the help of a PID controller. Experiments are performed on Oakwood disks (7 cm diameter and 2.5 cm height). The conductive heat source is maintained at different temperatures (46°, 61° and 70°C) and pressure in the chamber is controlled at different intervals (60-100, 150-200, and 250-300 mbar). Temperature inside the wood sample is obtained at two different positions. Conventional drying is carried out for comparison in a tunnel dryer. Antioxidant potential in fresh and dry wood samples is determined by using ABTS+• radical cation method. The top surface of vacuum-dried specimens is imaged with an HP scan. Finally it is shown that oak wood which is prone to discolour is degraded by different mechanisms depending on drying method. Our results suggest that oxidation of extractives and thermal degradation of hemicelluloses are the principal mechanisms of degradation, but its importance depends on drying method. Oakwood can be dried under vacuum conditions with an acceptable diminution of discolorations due to low temperature and reduction of oxygen amount with acceptable drying rates.
S Sandoval, W Jomaa, F Marc, J-R Puiggali
Investigation of chemical changes in acetylated beech wood during weathering
2009 - IRG/WP 09-40460
In this study Beech wood (Fagus orientalis) acetylated and has been subjected to a variety of artificial weathering conditions (water only, light only, water and light together)in difference times (0,50,150 and 300 h), then wood surface analyzed using Fourier Transform Infrared spectroscopy (FTIR).Results shown that weathering process affected the functional groups on the wood surface. Light and water, both acting together (full weathering) cause the greatest damage to the surface polymer structure and greatest chemical changes. The effect of light on the weathering process is quite rapid as monitored by FTIR spectroscopy within a few hours exposure (50 h).Changes observed in the infrared spectra of the surfaces after wood samples were subjected to water- only weathering are minor compared with the effect of light-only and water plus light. Acetylation of the wood under mild conditions servers to protect the surface from the weathering effect of light and water.
M Akhtari, M Arefkhani
New insights from NMR, FTIR, X-ray diffraction and physical chemistry into digestive processes in the wood-boring marine crustacean Limnoria quadripunctata
2010 - IRG/WP 10-10732
This paper summarises preliminary findings of a multi-technique exploration of the degradation of lignocellulose in the marine isopod Limnoria quadripunctata. Scanning electron microscopy revealed connections between the digestive gland and the hindgut that would permit the exchange of fluids between the two organs while the food mass is retained in place within the hindgut. This enables enzymes to be delivered to the substrate and breakdown products to be absorbed. FTIR and X-ray diffraction were used to show changes in wood chemistry during digestion. Cellulose crystallinity appears reduced after digestion, but lignin structure appeared little changed. NMR spectroscopy of animals under various feeding regimes measured the generation of breakdown products and levels of metabolites. Glucose was detected as a direct result of the animals feeding on 13C-labelled straw. This is the first direct evidence of total cellulose breakdown to the monomer. The importance of oxygen levels during digestion was shown by direct measurement with microelectrodes and indirectly by observing feeding on substrates impregnated with anti-oxidants. The hindgut lumen was found to be relatively anoxic. The antioxidant BHT significantly reduces feeding rates under laboratory conditions. These findings taken together give a picture of the effects of the activity of the recently described suite of digestive enzymes on their substrate.
G P Malyon, S LaBarre, N Kervarec, P Carey, J McGeehan, X Xie, A Klüppel, S M Cragg
Photostabilization of Wood with Higher Molecular Weight UV Absorbers
2010 - IRG/WP 10-30524
Higher molecular weight UV absorbers were created by reacting the epoxy-functionalized UV absorber 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) with maleic, phthalic or succinic anhydride. The ability of the UV absorbers to photostabilize wood was then examined. FTIR-spectroscopy confirmed that HEPBP reacted with phthalic anhydride to create a polyester that preserved the UV-absorbing benzophenone group. There was less evidence that the polyester was formed when HEPBP was reacted with maleic or succinic anhydride. HEPBP-phthalic anhydride was the most effective UV absorber at photostabilising wood. This UV absorber showed increased UV absorption around 270 nm, formed a leach-resistant film at wood surfaces and was able to restrict both weight and tensile strength losses of thin wood veneers during accelerated weathering, unlike chromium trioxide and a UV absorber-hindered amine light stabilizer. We conclude that higher molecular weight polyester-type UV absorbers show promise as a way of photostabilizing wood and briefly discuss how more effective systems could be developed.
P D Evans, M J Chowdhury
Silicon compounds as additives improving alkyd-based wood coatings performance
2010 - IRG/WP 10-40531
The reactivity of cellulose with solvent-born alkyd-based wood coatings supplemented with organosilanes was analyzed. Structural analysis of cellulose subjected to the reaction with organosilanes and following extraction with water was performed using Fourier-transform infrared spectroscopy (FTIR). The analyzed IR spectra comprise bands 1250 cm-1 typical for the SiC group and 800 cm-1 typical for vibrations of SiC and/or SiO groups. The presence of these bands in the spectra proves the occurrence of a reaction between cellulose and organosilanes. Silicon concentration in cellulose was determined by AAS after the reaction with coating system after leaching.
B Mazela, I Ratajczak, K Wichłacz-Szentner, P Hochmańska
Multilayer hot-press drying and chemical modifying of poplar wood with urea-formaldehyde prepolymer
2011 - IRG/WP 10-40539
The objective of this study was to determine the technology of chemical modifying and multilayer hot-press drying on poplar wood. The chemicals were impregnated into cell lumen space by pulse-dipping machine to improve the dimension stability and mechanical property of timber. The timbers were compressed and dried by the multilayer hot-press drying to increase the density of timber. Results indicate that the physical and mechanical properties were compared between modified timber and natural timber. Based on the findings, the results demonstrated that the density of modified wood improves by 58.1 %, the hardness of the end profile surface improves by 66.6 %, while tangential direction 210 % and radial 160 %, the bending strength improves by 77.8 %, the bend elastic modulus improves by 66.3 %. The improvements of mechanical property were owed to the reinforcement of chemical on the cell wall and lumen space of wood. Characteristics of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) for modifying were studied using FTIR spectrometer and XRD instrument. The intensity of hydroxyl absorption peak in the infrared absorption spectrogram decreased significantly, and that of carbonyl decreased lightly. The C=O absorbance at 1750 cm-1 reduced as result of the deacetylation of hemicelluloses and reaction between C=O and -NHCH2OH of urea-formaldehyde prepolymer.. The crystallinity of wood decreased lightly from 39.65 % to 37.06 %. Fourmorphologic models of chemical within wood were discovered by SEM.
Guofeng Wu, Yifei Jiang, Sheng Yao, Junwen
Characterisation and evaluation of various chitosan oligomers, and decay resistance
2011 - IRG/WP 11-30562
Chitosan, a polymer of D-glucosamine, is known for its antimicrobial activity. However, the physicochemical properties of chitosan depend upon three principal factors, i.e. source of raw material, molecular weight and degree of deacetylation. Here, we report synthesis and characterization of chitosan oligomers prepared by deaminative depolymerization of chitosan (s) obtained from Sigma Aldrich and China (industrial grade). Subsequently their antifungal activies were evaluated using both agar nutrient medium and wood decay bioassays. The nutrient medium bioassay results showed that chitosan(s) and chitosan oligomers affected mycelial growth to different magnitudes. Nevertheless, two of the low-MW chitosan oligomers completely inhibited the growth of all the tested fungi as compared to high-MW chitosan oligomers. However, the work presented in this paper, depicts that antifungal activity increases by decreasing the degree of polymerization of chitosan oligomers, which is a contrary to the reported literature. The wood decay trial confirmed the antifungal activity of chitosan oligmers against basidiomycetes but highlighted the leachability of chitosan when exposed to water.
I Hussain, C Chittenden, T Singh
Study of UV resistance and natural weathering of coatings on chemically modified wood
2013 - IRG/WP 13-40629
In this study, UV resistance and weathering performance of rubberwood (Hevea brasiliensis) and radiata pine (Pinus radiata) modified with benzoyl chloride and acetic anhydride was studied. Performance of polyurethane based wood coatings on modified wood was also evaluated. Unmodified and chemically modified specimens were exposed to accelerated and natural weathering. Modified and unmodified wood specimens were coated with commercially available polyurethane based transparent and opaque finishes and exposed to natural weathering for a period of 2 years. Physical and chemical deteriorations on uncoated / coated wood panels due to weathering were periodically monitored. Analysis of colour changes and chemical deteriorations of weathered specimens showed rapid discolouration and lignin degradation on unmodified wood surface exposed to weathering. Modified wood showed resistance to weathering and was partially effective in inducing UV resistance as compared to unmodified wood. Results clearly indicate that performance of coating can be significantly improved by chemically modifying wood substrate with benzoyl chloride. Benzoylation of wood polymers improved coatings adhesion and enhanced life of paints by 3-4 times. The performance of opaque coating was better than transparent coating, presumably due to photodegradation of wood substrate in transparent coating.
K K Pandey, K Srinivas
Effect of Nano-silver and Nano-copper and Nano-zinc oxide on Paulownia wood exposed to white-rot fungus
2013 - IRG/WP 13-30635
Paulownia is known as a fast growing tree and it can be used in several applications. The present study investigated the effect of Nano-silver and Nano-copper and Nano- zinc oxide on resistance of Paulowina (Paulownia fortunei) wood against the white rot fungus (Coriolus versicolor). Wood specimens with a dry density of 0.37g/cm3 were impregnated with a 400 ppm aqueous suspension of micronized nano-silver and nano-copper with particle sizes ranging from 10 to 80 nm , in a pressure vessel at 2.5 bars for 20 minutes. Treated specimens were inoculated with the fungus and incubated for sixteen weeks at 26˚C with 65% relative humidity in accordance with the EN113 standard. After incubation the mean percentage weight losses of specimens were measured. Percentage weight loss of control samples was much higher than treated ones. Results of the analysis of variance showed that the impregnation of wood with nanosilver, nanocopper and nanozinc oxide significantly increases the decay resistance of Paulownia against this white rot fungus.
M Akhtari, M Ganjipour
Effectiveness of Copper Indicators in Treated Wood Exposed to Copper Tolerant Fungi
2014 - IRG/WP 14-20554
Wood treated with a copper based wood preservative will typically turn a green color. While the depth of copper penetration can be readily discerned from the green color of the copper it is standard practice in research and commercial treating plants to make use of a color reagent such as Chrome Azurol S, Rubeanic acid or PAN indicator to reveal the penetration more clearly. When copper treated wood is exposed to copper tolerant fungi discoloration of the original green color can occur. Reactivity of the treated wood with the color reagents can also be impaired. In this paper, the effectiveness of copper color indicators in detecting copper in wood attacked by copper tolerant brown rot fungi at early and late stages of decay was evaluated. Neither Chrome Azurol S nor PAN indicator could detect copper in the area where incipient and severe decay took place, even when chemical analysis showed significant levels of copper in these areas. Rubeanic acid was the only indicator which provided positive identification of copper in these samples. An FTIR study demonstrated that the loss of green color in copper treated wood by copper tolerant fungal attack is closely related to the formation of copper oxalate. The finding supports the theory that copper oxalate detoxifies copper and acts as a precursor for decay since a significant amount of copper oxalate was found in the area with discoloration but no visual decay, as well as in the area with severe decay. The results from this study suggest that the ineffectiveness of Chrome Azurol S and PAN indicators may be due to their inability to replace oxalate ion to form the colored complex with copper.
L Jin, K Brown, A Zahora, K Archer