Your search resulted in 68 documents. Displaying 25 entries per page.
Curing kinetics of nano cupric oxide (CuO) modified PF resin as wood adhesive: Effect of surfactant
2013 - IRG/WP 13-40620
The effect of nano cupric oxide (CuO) in combination with surfactants on the curing kinetics of phenol formaldehyde (PF) resin, as well as the bonding strength of plywood prepared using the modified resin were investigated in this study using dynamic and isothermal differential scanning calorimetry (DSC). The result showed that the incorporation of nano CuO along with alkane surfactant made in the laboratory clearly reduced the apparent activation energy of the PF resin and improved the addition and condensation reactions of the PF resin. Inclusion of the surfactant had the further effect of compensating the influence of diffusion control caused by nano CuO alone. The shear strength of plywood suggested that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosolfonate (0.55%) in the PF resin mixture was sufficient to meet the requirement of wood-based composites manufacturing.
Wei Gao, Guanben Du
Confocal laser scanning microscopy of a novel decay in preservative treated radiata pine in wet acidic soils
1997 - IRG/WP 97-10215
Light microscopy of radiata pine (Pinus radiata D. Don) field test stakes (20x20x500mm3) exposed in wet acidic (pH 3-4) soil for 12 - 24 months showed predominance of an unusual type of decay characte-rised by tunnelling attack of wood cell walls. After two years decay was moderate to severe in wood treated to ground contact CCA specifications and also equivalent retentions of creosote, and a number of new generation preservatives. Relative to other New Zealand temperate test sites and also an Australian tropical site, the New Zealand acidic soil test site was very aggressive. Correlative scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to elucidate the micromorphology of this attack. Tunnels of diameter 0.2-5 µm were present throughout all layers of the cell wall, and their orientation was not related to cellulose microfibril orientation. They also showed no preference for particular cell wall layers, indicating a lignin degrading capability. CLSM images showed that living, connecting fungal hyphae were present in the cell lumina and tunnels. This type of attack was predominant in wood that was highly saturated with water whereas wood that was less moist was predominantly attacked by classical white rot. Ongoing isolation and incubation studies in conjunction with further microscopy should enable identification of the fungal species involved.
R N Wakeling, Ying Xiao, A P Singh
Soft rot cavity widening - A consideration of the kinetics
1984 - IRG/WP 1227
Studies on the micromorphology of soft rot cavity formation by Phialophora hoffmannii in birch using time-lapse cinemicrography are briefly outlined. A mathematical model is constructed to describe the cavity widening process, particularly changes in the surface area of a hypothetical cavity during enlargement. On comparison with observed data it is concluded that the rate of cavity widening is determined by wood cell wall characteristics.
M D C Hale, R A Eaton
A discussion of current theories concerning CCA fixation
1983 - IRG/WP 3238
The understanding of the fixation mechanism of CCA and related preservatives in wood has been greatly improved by a significant series of recent scientific papers. In view of recent concerns in New Zealand regarding the long-term efficacy of CCA in high decay-hazard situations, it was considered appropriate to review this recent work and to contrast it with theories presented by previous workers.
D V Plackett
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
Kinetic modelling of adsorption of quaternary ammonium compounds by Scots pine wood sawdust (Pinus sylvestris L.)
2005 - IRG/WP 05-30369
The adsorption of new quaternary ammonium compounds from aqueous solutions onto Scots pine wood (Pinus sylvestris L.) sawdust was studied. The pseudo first- and second- order kinetic models were used for the mathematical description of the sorption dynamic process of QACs onto wood. The highest correlation coefficients were obtained for the pseudo-second order kinetic model, those suggest that chemisorption is involved in the adsorption process.
A fixation model, based on the temperature dependence of CCA-C fixation
2000 - IRG/WP 00-40163
A model was prepared for the fixation of 1% CCA-C in red pine that allows the prediction of extent of fixation based on the temperature history of the treated wood following pressure treatment. The reaction kinetics of the rapid initial reaction and the slower main reaction were characterized using the Van t'Hoff equation. The initial reaction could be represented by a 10th order chemical reaction and the main reaction by a first order chemical reaction. The main reaction zone in red pine starts once approximately 47% of the total Cr VI in the impregnated CCA-C solution is fixed on wood matrix and is much slower so it controls the fixation rate. The rate constants for the two zones were estimated at a range of fixation temperatures and the temperature dependence defined by the Arrhenius equation. The rate equation and the temperature dependence were combined in a single model for each fixation zone providing an equation that related extent of fixation to the time/temperature history following fixation. The model accurately predicted fixation rate of pine poles exposed to variable temperature conditions following treatment in most cases, although slight changes in the reaction and Arrhenius constants due to natural variability in wood density and other properties could result in relatively large errors in some cases.
P A Cooper, K M F Kazi, Jianbin Chen, Y T Ung
Differential behaviour of wood rotters at water repellent Rubberwood
2000 - IRG/WP 00-10386
Rubberwood samples treated with different concentration of aqueous solution of chromic acid has induced significant increase in water repellency and attains dimensional stability. Though water repellency and dimensional stability was achieved by treatment, the fungal invasion could not be completely controlled. Differential level of decay of brown and white rot in wood treated with water repellent compound is observed. Wood shows complete protection from white rot but failed to prevent the invasion of brown rot in water repellent rubber wood. These treatments were found to be very effective even at a low concentration of 2.5% in protecting decay due to white rots as compared to brown rot. Effectiveness of these treatments against white rot may be attributed to formation of lignin-chromic acid complex.
H C Nagaveni, S S Chauhan, K S Rao
SEM of wood dust particles
1997 - IRG/WP 97-50084
Dust particles from beech and oak trees have been classified in Germany as being "working materials which are definitely carcinogenic to humans". All other wood dusts, including those from softwoods, are classified as being materials "with reasonable suspicion of carcinogenic potential". The carcinogenic principle of action continues to remain unclear. The mechanical irritation is one of a number of possible triggering principles. In this connection the morphology of the dust particles is of decisive importance. With the aid of a scanning electron microscope this study characterises the dust from spruce, Scots pine, beech and oak. With regard to shape and size the dust particles of all sample collections were divided into 5 groups with principle structural similarity. Therefore a different particle morphology with correspondingly different mechanical irritation in the nose can not be the main principle of action. When compared to asbestos fibers, the small amount of fibrous dust particles as one of the five groups could be clearly distinguished by their structure and dimensions. Mechanical irritation as the main principle of action in the formation of malignant nasal tumors is also contradicted by the findings of different working groups which have established a strong association between hardwood dust and adenocarcinomas of the nasal cavity and paranasal sinuses, and a connection between softwood dust and other types of nasal carcinoma.
U Schmitt, R-D Peek, A O Rapp
The use of immunofluorescence labelling for detecting Ophiostoma piceae in radiata pine
1998 - IRG/WP 98-10268
The primary objective of the current investigation is to understand fungal interactions of dominant sapstaining fungi in radiata pine using confocal laser scanning microscopy (CLSM). In the current paper, an immunofluorescence labelling technique was developed for detection of Ophiostoma piceae using a monoclonal antibody. The primary antibody was labelled with Oregon green 514 Goat anti-mouse IgG fluorescent dye before examining with CLSM. The study showed that immunofluoresence labelling was achieved satisfactorily for detecting fungal hyphae of Ophiostoma piceae but not for some other important sapstaining fungi that occur in radiata pine.
Ying Xiao, B Kreber, C Breuil
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
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
Termite and fungal resistance of in situ polymerized tributyltin acrylate and acetylated Indonesian and USA wood
2000 - IRG/WP 00-30219
Wood [Indonesian pine (IP), Indonesian Jabon (IJ) and USA southern yellow pine (USP)] was either in situ polymerized with tributyltin acrylate (TBTA) or acetylated and then exposed to termite and fungal degradation both in laboratory tests and field exposure. The TBTA woods had an average weight percent gain (WPG) of 11% for IP, 12% for IJ, and 10% for USP. The acetylated woods had a WPG of 15-27% for IP, 16% for IJ, and 12-21% for USP. All levels of TBTA and acetylation treatments were effective against the brown-rot fungus Tyromyces palustris and the white-rot fungus Coriolus versicolor in laboratory testing. Resistance to subterranean termites [Coptotermes gestroi (Wasmann)] and dry wood termites [Cryptotermes cynocephalus (Light)] was shown in laboratory tests with all treatments. After one year of field testing in Indonesia (AWPA Standard E7-93), TBTA treated specimens gave a grade number of 8 for all 3 woods compared to 0 for the untreated controls (based on a 10 - point scale.) The acetylated specimens gave a grade number of 4 for IP, 8 for IJ, and 6 for USP. Scanning electron microscopy (SEM) showed polymer located in the lumen of the earlywood and latewood of selected TBTA treated specimens, but at low overall polymer weight gain the lumens were not evenly filled. Termite field testing continues on all treated wood specimens.
R E Ibach, Y S Hadi, D Nandika, S Yusuf, Y Indrayani
Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 5: Effect of wood species and preservative composition on the leaching during storage
1975 - IRG/WP 354
Conversion reactions during storage of CCA treated wood take place even at and below the fiber saturation point as long as ion transport is possible. Increase in drying temperature increases the final pH of the treated wood and the leachability of Cu and decreases slightly the leachability of Cr, while the leachability of As is not affected. This temperature effect is considered to be of no technical importance, but may be of importance when preparing material for biological testing. The length of the wet fixation period before the drying does not influence the results. The presence of alkali sulfates in some preservatives affects the pH of the unleached wood but not the leachability of the active elements. The natural pH of the wood determines to a considerable extent the final pH and the leachability. A correlation was established between the leachability of Cu and As versus the final pH in wood. When treated with 2-2.5% preservative solutions some wood species: Douglas fir, Ponderosa pine and to a lesser degree Southern yellow pine, showed unexpectedly high As leachability, while on doubling the concentration normal leachability data were obtained. The study included three commercial CCA preservatives: Boliden K33, Celcure AP and Tanalith C, and one experimental variety of Celcure AP without sodium sulfate.
Studies of the ray parenchyma cell ends on the radial flow of Sitka spruce (Picea sitchensis)
2000 - IRG/WP 00-40164
It is widely accepted that either ray tracheids or ray parenchyma cells offer the major flow pathways radially for the impregnation of softwood with preservative chemicals. It is now generally recognised that, if radial flow does occur through ray parenchyma cells, the cross-field pits play a dominating role for the liquid movement in the radial direction. In this case, the radial flow of fluid is through the ray parenchyma cells to the longitudinal tracheids across cross-field pit apertures and then back again to the other ray parenchyma cells. It is in this context that cross-field pits which favours flow in the radial direction via a longitudinal route, and thus gives a long path length for radial flow. However, the presence of small channels (i.e. simple pits) between the two ray parenchyma cells may also have a recognisable influence on the radial flow, and exceed the continuous pathway for liquid movement. In this study, therefore, the anatomical structure (the end platform angle, the number of the simple pits per ray parenchyma cell end, their dimensions and the changes in dimensions across growth rings) of the ray parenchyma cell ends have been examined by scanning electron microscope (and microscopic images were then analysed by image analyser) to explain the differences in radial permeability between the extremes in the radial treatment data.
Confocal Laser Scanning Microscopy (CLSM) of decayed wood
1998 - IRG/WP 98-10273
Confocal laser scanning microscopy (CLSM) is currently being used to examine biodegraded wood and is proving to be a useful new technique in this area of work. Non-invasive optical sectioning within a thick specimen (20 - 50 µm), coupled with post image processing techniques allows manipulation of images and 3-D reconstruction from serial sections. Glutaraldehyde can cause cell autofluorescence, and since wood cell components do not react with it, a relatively simple technique for localising fungal hyphae, using glutaraldehyde as a fixative, was developed. Subsequent use of probes specific for chitin provided superior images of fungal hyphae in wood. High resolution, sequential, 2-D images can be produced to determine the mode of fungal attack within a thick wood specimen in a dynamic way. Voxel 3-D reconstruction of a series of image stacks enabled stereo viewing of objects.
Ying Xiao, R N Wakeling, A P Singh
Differential susceptibility of living and dead timber to colonisation by sapstain and mould fungi
1998 - IRG/WP 98-10288
Field studies have revealed that when timber is irradiated (i.e. killed) it is more susceptible to colonisation by mould fungi than sapstain fungi. By comparison, freshly sawn timber shows very little mould colonisation, tending to be colonised by sapstain fungi. It appears, therefore that the physiological state of the wood may influence the pattern of colonisation. A laboratory trial was undertaken to investigate in more detail the observations recorded in the field studies. A spore suspension of the mould Trichoderma was used to inoculate one set of living and one set of gamma irradiated (dead) wood blocks; similar sets of blocks were inoculated with a spore suspension of the sapstain fungus Ophiostoma piceae and a final treatment consisted of inoculating further sets of blocks with a mixed spore suspension of both fungi. Results clearly indicated that Trichoderma rapidly colonised and discoloured the irradiated blocks whereas there was very little defacement on the living blocks. The dead wood blocks inoculated with the mixed spore suspension were also rapidly colonised by the mould Trichoderma and 0. piceae was clearly out competed. However the living wood blocks were predominantly colonised by 0. piceae when they were inoculated either alone or in combination with Trichoderma. The factors controlling these patterns of colonisation are being investigated.
J R Williams, D J Dickinson, J F Webber
Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 6: The length of the primary precipitation period
1975 - IRG/WP 359
The end of the primary precipitation fixation period of CCA preservatives coincides with the first peak in pH versus time. This offers a simple way of estimating the duration of the period. The duration is determined by a number of factors and their interactions, the most important of which are: wood species (anatomy, natural pH, accessibility of reducing agents), preservative type, preservative concentration and temperature. For interpretation of experimental data the effect of these factors is discussed in the light of the chemistry and the mechanism of fixation of CCA preservatives. For a proper handling of the treated timber, knowledge of the duration in actual working conditions is essential.
Durability aspects of (hydro)thermal treated wood
2000 - IRG/WP 00-40160
Samples of several wood species were treated in a two steps process, subsequently hydrothermal and dry heat-treated, by the so-called PLATO-process and analysed for their resistance against fungal attack. Both PLATO-treated and dry heat-treated specimen were prepared and analysed, in order to study the influence of moisture during hydrothermal treatment of wood. The resistance against all of the studied types of fungi was improved considerably after the PLATO-treatment. Especially the resistance against brown rot fungi was increased by the treatment. Also the resistance against white rot and soft rot was improved. The increase of the decay resistance was found dependent on the applied process conditions. The PLATO-treatment was found to be more efficient compared to a one step dry heat-treatment, with respect to improving the resistance against fungal attack. The effectiveness of the treatment is improved by applying a hydrothermal step before the dry heat-treatment step. The process conditions in the curing step appeared to have the largest effect on the resistance against soft rot and brown rot decay. White rot decay was less dependent on the curing conditions and found more affected by the hydrothermolysis, suggesting the decomposition of hemicellulose in the hydrothermolysis.
B F Tjeerdsma, M Stevens, H Militz
Visualising Bacteria in Wood Using Confocal Laser Scanning Microscopy (CLSM)
1998 - IRG/WP 98-10272
A fluorescent phospholipid probe was used in conjunction with confocal laser scanning microscopy (CLSM), to visualise bacteria which inhabit in radiata pine wood and degrade pit membranes. CLSM has the ability to collect fluorescent images through different emission filters at the same time, so it is possible to distinguish gram-positive and gram-negative bacteria in infected wood by counterstaining wood sections with specific fluorescent stains. Images obtained using CLSM were compared with those acquired using light microscopy (LM) and scanning electron microscopy (SEM). Strong fluorescence of the phospholipid probe made it possible to visualise bacteria in wood even when present in numbers too small to detect by LM or SEM.
Ying Xiao, A P Singh, R N Wakeling
Investigation of extracellular mucilaginous material in some wood decay fungi
1996 - IRG/WP 96-10188
The external morphology of the extracellular mucilagenous material (ECM) produced by Coriolus versicolor and Coniophora puteana during colonization of Scots pine and beech was studies using SEM. Specimens were examined in the frozen hydrated, freeze-dried and critical point dried state. All technics produced artefacts but the ECM was best preserved when examined the frozen hydated state. Critical point drying damaged the ECM extensively but was useful in partly explaining its nature. ECM was found to line much of the lumen and coated aerial fungal mycelium. Some morphological patterns in which the ECM and fungal hyphae were involved are also descibed.
A R Abu, D J Dickinson, R J Murphy
The kinetics of anhydride modification reactions of wood. Experimental results and theoretical modelling
1998 - IRG/WP 98-40125
Although the chemical modification of wood remains a fertile area for research, there has been little work performed on the kinetics of the modification process. The reaction kinetics of a series of linear chain and cyclic anhydrides has been studied and activation energies of the reaction determined. The reaction kinetic profiles are determined by the relative rates of reaction of the reagent with the cell wall polymeric hydroxyl groups, and the rate of diffusion of the reagent within the bulk of the substrate. Thus initially, the rate of reaction is determined by the reaction of reagent with surface sites, but as reaction proceeds, diffusion processes begin to dominate. The relative contributions of the two processes depend upon a number of variables, which include size of reagent, reaction temperature, and ultrastructure of the substrate. This process has been modelled using percolation theory, which has previously had extensive application in describing the flow of liquids through complex porous media, yet has not been applied to wood. The modelling shows that the reaction profiles are determined by the relative rates of reaction and diffusion.
C A S Hill, J G Hillier
Kinetics of the dissociation of Cr, Cu, and As in fixed CCA-treated wood
2001 - IRG/WP 01-50168
The results of an experiment showing the kinetics of the dissociation of CCA compo-nents in water within treated wood samples are presented. Dry red pine (Pinus resinosa Ait.) samples were simultaneously vacuum-treated with water, then expressed to re-move the water at successive time intervals. The expressate was then analyzed for Cr, Cu, and As concentration by inductively coupled plasma (ICP). Dissolved ion concen-trations increased for approximately 24 hours then reached relatively high equilibrium values which did not seem to depend on CCA loading in the wood. This detailed kinetic information is essential to understanding and predicting the leaching of fixed CCA.
L Waldron, P A Cooper
Immuno-scanning electron microscopic localization of extracellular polysaccharidases within the fibrillar sheath of the brown rot fungus Postia placenta
1991 - IRG/WP 1497
Extracellular polysaccharidases of the brown-rot fungus Postia placenta were localized using colloidal gold labeled monoclonal antibodies to the B-1,4-xylanase (32-36kDa) fraction of Postia placenta. Postia placenta was grown from agar onto glass coverslips, immunolabeled with or without prior fixation, and examined by SEM. Enzymes were localized on the hyphal surface and on the clumped fibrillar elements (mycofibrils) of the hyphal sheath following fixation with enzymes. If fixation was omitted, labeling was diffuse and not localized on individual or clumped mycofibrils. We conclude that extracellular decay enzymes are weakly bound (non-covalently), but not identical to, the linear mycofibrillar elements of the hyphal sheath. Enzymes appear to dissociate into the water soluble glucan matrix of the sheath during incubation in physiological buffers when fixation is omitted.
F Green III, C A Clausen, M J Larsen, T L Highley
Differential retention and leaching of CCA (C) in sapwood and heartwood of Kenyan-grown blue gum (Eucalyptus saligna) and black wattle (Acacia mearnsii)
2005 - IRG/WP 05-30371
Retention and leaching of CCA(C) in small samples of sapwood and heartwood of Kenyan-grown blue gum (Eucalyptus saligna) and black wattle (Acacia mearnsii) were tested under laboratory conditions. Clear samples (100mm x 30mm x 40mm) were removed from the sapwood and heartwood of sampled defect-free and sound plantation trees of the two species. These were separately air-dried to 15% MC, end-sealed and pressure-treated with 3% CCA-C (oxide) at a commercial treatment plant. They were then conditioned at ambient temperature, air-dried to 15% MC and retentions calculated on a weight-gain basis (E. saligna: sapwood - 33.3 Kg/M3, heartwood - 6.4 Kg/M3; A. mearnsii: sapwood - 28.7 Kg/M3, heartwood - 5.6 Kg/M3). Batches of samples of sapwood and heartwood of each species were then separately leached in running tap water for 3, 6, 9, 12, 15, 18 and 21 days. After each leaching period, batches of samples were removed, oven-dried to 15% MC, and the amount of preservative leached calculated on a weight-loss basis. After 21 days of leaching, substantial amounts of the preservative were removed from sapwood samples (E. saligna - 44.1%; A. mearnsii - 47.7%), whereas losses of the preservative from heartwood samples were significantly lower, 18.7% and 16.1% for E. saligna and A. mearnsii respectively. The results indicate that although retentions may be higher in sapwood than in heartwood of these two species, fixation of CCA appears to be poorer in sapwood, resulting in higher losses of the preservative through leaching. Mechanisms responsible for differential retention, fixation, and leaching of CCA in sapwood and heartwood on these two species need to be further studied and documented.