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Decay resistance of densified ammonia-plasticized stems of oil palm (Elaeis guineensis)
1991 - IRG/WP 3673
When wafers of oil palm stems (Elaeis guineensis) were plasticized with 28% aqueous ammonia and immediately compressed mechanically, the treated material, gained 73% in basic density (average basic density, 0.695 g/cm³), and was highly resistant to decay by wood rot basidiomycetes. Compared with the control specimens (density, 0.403 g/cm³), resistance to decay of the densified specimens by Coriolus versicolor increased by 55%, and Gloeophyllum trabeum, 74%. Fungal decay was significantly correlated with basic density (densification effect) (r-value, between -0.77 and -0.92), mediated in part by a similar pattern of correlation (-0.86) between densification and decaying tissue moisture content. Mass losses of specimens which were plasticized but not subsequently densified, did not differ significantly (P<0.05) from the controls while basic density of such treated specimens decreased slightly (density, 0.358 g/cm³). Total nitrogen contents for the controls, specimens plasticized without densification, and densified plasticized specimens were respectively; 0.24, 0.65 and 0.63% (g/g), the control differing significantly from the rest. Substrate pH were similar among the three samples. It appeared that artificial densification (rather than total nitrogen levels) assumed an overriding influence on decay resistance of compressed ammonia-plasticized oil palm stems
A H H Wong, M P Koh


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


Effect of Nano-silver Treatment on Densified Poplar Wood Properties. Part Two: Spring Back, Compression set, Impact Load Resistance and Hardness
2011 - IRG/WP 11-40568
This paper is the second part of the study of applying nano-silver treatment before densification of poplar wood (Popolus alba). The specimens were prepared in four groups of: 1) nano-silver impregnated 2) water impregnated 3) dried with no impregnation and 4) the control specimens. The impregnation process was done by empty cell process. Then, the groups of 1 to 3 were compressed in a hot press at the temperatures of 150 and 175ᵒc for 1 and 4 hours. Spring-back, compression set, impact load resistance and hardness values of specimens were determined and all data were analyzed statistically. The measurements of mechanical properties were carried out according to ASTM D-143. The results showed that by nano-silver treatment, spring back, compression set and impact load resistance were improved, significantly. The best amounts of spring-back (0.24%) and compression set (35.26%) were seen in specimens which were impregnated with nano-silver solution and compressed at 175 for 4 hours. The best amount of impact load resistance (34915.0 J/m2) belonged to the nano-silver treated specimens which were compressed at 150 for 4 hours. The maximum amounts of hardness values (37.16 N/mm2) were related to the non-treated specimens which were compressed at 175 for 4 hours. On the whole, based on the results of part one and this one, applying nano-silver treatment can be resulted in obtaining optimal physical and mechanical properties in densified poplar wood. The results of this study will be useful for producing a novel densified wood which can be applicable for some structural uses such as flooring.
G Rassam, H Reza Taghiyari, B Jamnani, M Ali Khajeh


State of Nanocopper Fixation by Steam-Densification
2016 - IRG/WP 16-40723
This study was aimed to investigate the effect of steam treatment before densification on leachability and dimensional stability of nanocopper impregnated poplar (Popolus alba). Wood samples were impregnated with nanocopper suspension (200 and 400 ppm) for 20 minutes under 4 bar pressure. Steaming process was done before densification at 150°C for 2 hour. Radial densification (33%) was done consequently at 170°C for 30 min. Spring back (spontaneously after press and after 15 and 30 days), long term water absorption (LWA) and radial swelling (LRS) after (2hrs, 24hrs,48hrs, 1 week, 2 weeks, 3 weeks, 4 weeks and 8 weeks) soaking in water were measured and all data analysed statistically. Leaching test was carried out according to EN84, 1997. Results showed steaming and densification had negative effect on nanocopper fixation in wood samples and nanocopper leaching significantly increased in steamed densified samples. The highest leaching values belonged to 400ppm impregnated samples steamed and densified. 200ppm impregnated densified samples had significant decrease in copper leaching comparing to steamed densified samples but the values were still over the safety limit. In non densified samples impregnated with both concentrations of nanocopper, the leaching values were at the safety limit. Highest spring back values were seen after 15 and 30 days at either concentration of nanocopper. The least water absorption was seen in steamed densified samples whereas the least radial swelling was seen in non-densified samples. This study proves that nanocopper impregnated densified or steamed densified poplar are not suitable for humid condition where wood is in contact with ground or water.
G Rassam, A Talaei, A Ahmadi


Markers of quality in self-bonded beech boards
2017 - IRG/WP 17-40820
A self-bonding phenomenon takes place when five layers of beech (Fagus Sylvatica L.) veneers are pressed at temperatures higher than 200ºC. If the pressing temperature between veneer surfaces reaches at least 225ºC during pressing and if the pressure applied is optimal, water-resistant bonds are formed between veneers. This study investigates the relation of thickness reduction (marker of compression) and mass loss (marker of heat treatment intensity) to boards quality. The effect of water and water vapour on the bondings between veneer in boards pressed at 200, 225 and 250ºC is studied. The conclusion is that pressing 5 layers of 2 mm rotary-cut beech veneer parallel-fibered at 225ºC, 5 MPa and 300 s leads to a thickness reduction of 33.4 % and mass loss of 1.23 %; in such boards bondings are not resistant to liquid water but are resistant to vapour after one adsorption-desorption cycle. When pressing at 250ºC, 5 MPa and 300 seconds, the thickness reduction is 50% and the mass loss 4%; in such boards no delamination was observed when soaked in water. Boards pressed at higher temperature show lower hygroscopicity. Their equilibrium moisture content (EMC) ranged between 3.6 and 7%. Based on the results of this study it is hypothesised that the decay resistance of self-bonded boards will increase when increasing the severity of the hot-pressing.
C Cristescu, D Sandberg, O Karlsson


Understanding of the effect of ancestral and natural saltwater treatment on durability, fibers densification and chemical modification of palm wood
2018 - IRG/WP 18-10921
The palm-tree sector plays a very important role on both the socioeconomic and ecological levels, in Tunisia. There are three million trees in Tunisian palm plantations, ensuring a potential significant wood production, mainly in the craft and furniture industries. In the past, Date Palm wood (Phoenix dactylifera L.,) was also used as structural material. Its low natural durability and its low mechanical properties were improved by an ancestral preservative method consisting in the immersion of the trunk of the palm tree trunk freshly slaughtered for a period ranging from 1 to 2 years (depending on the species) in the salt waters of the Lake of Chot Djerid. This ancestral practice was disappeared, and it is always difficult to find more information on the different parameters involved in this kind of process. The objective of this work was to assess the main technological qualities of palm wood preserved by salting while trying to retrace the steps of this natural and eco-friendly preservation process. Two Common date palm cultivars woods (Kentichi and Deglet Noor) with ages ranging from 40- to 50-years, native and preserved by salting in the Chot Djérid were used for the experiments. Each wood samples were collected at the Regional Center of Research on Oasis Agriculture - Degache - Southern Tunisia. Densities (air-dried, water saturated, basic), mechanical properties, decay and termites resistances tests were performed on native and salt water - treated palm woods. The first results showed a significant increase of the air-dried density of palm wood samples which increases after their wood salt water immersion. Salt water treatment allows improving greatly the palm wood MOR in bending and paralleling to the fibers. Termite’s resistance tests highlighted that native and treated palm wood had a similar degradation level after termite exposure, but the termite mortality rate was higher for the treated wood than that of native palm wood. Extractives, lignin and cellulose contents are slightly more abundant in the control samples except for the hemicelluloses which are more abundant in the treated palm wood sample. Additional analyses conducted with an ICP-AES 700 Agilent device, evaluating the mineral compositions between native and salt-treated palm woods, give us some explanation ways about the performance improvement of wood after such a natural preservation process.
M T Elaieb, A Namsi, M Tella, M-F Thévenon, K Chandelier


Evaluation of chemical densification of three hardwood species through in-situ electron beam polymerization
2020 - IRG/WP 20-40893
Hardwoods are the most suitable species for wood flooring for their appearance as well as their hardness. Yet, improving hardness can provide substantial benefit for the wood flooring market. Chemical densification of wood and in-situ polymerization through electron beam technology was chosen to increase hardness of three hardwoods (Yellow birch (YB) (Betula alleghaniensis Britt.), Sugar maple (SM) (Acer saccharum Marshall) and Red Oak (RO) (Quercus rubra L.)). Monomer formulations were chosen for their viscosity. Impregnation was carried out through a simple vacuum process and was followed by 100 kGy electron beam irradiation to allow in-situ polymerization. Successful polymerization was proved by infrared spectroscopy and thermogravimetric analysis. Chemical retention and hardness of densified and reference samples were measured. Chemical retention (CR) varied between the three species being the lowest for porous red oak and the highest for diffuse porous yellow birch. CR also decreased with increasing viscosity of the impregnant for SM and YB. However, viscosity did not affect chemical retention of RO samples. Hardness of wood increased substantially for all treatments and all species and was comparable to that of Jatoba. Densified YB samples showed greater improvement of hardness compared to RO and SM due to higher chemical retention. Results also showed that with low chemical retention, hardness was improved but densified wood hardness is mostly influenced by wood properties. While the three species showed significant hardness improvement, yellow birch seems more suitable for densification.
J Triquet, P Blanchet, V Landry


Surface chemical wood densification through in situ electron beam polymerization: description and dose study
2022 - IRG/WP 22-40933
Traditional wood chemical densification processes can be used to improve wood mechanical properties by increasing density of the material throughout its thickness. While mechanical surface densification has heavily been investigated, surface treatments involving impregnation of monomers remain unexplored. This study describes a new material, surface densified through lateral impregnation of acrylate monomers and their in-situ polymerization using high-energy electron beams. Yellow birch (Betula alleghaniensis, Britt.) was surface densified and its morphology was studied using X-Ray density profiles and microtomography. Brinell hardness of densified samples increased while irradiated controls showed lower hardness compared to untreated controls. Effect of electron beam dose was studied at 25, 50 and 100 kGy. Using acetone extraction and GC-MS, residual monomers were found at low dose while degradation of wood was observed ah higher dose using FT-IR. This study demonstrates how carefully choosing the electron beam dose impacts the material in different ways.
J Triquet, P Blanchet, V Landry


Effect of densification of Eucalyptus nitens and E. obliqua on moisture uptake, swelling, decay resistance, and fire performance
2022 - IRG/WP 22-40946
Some Australian Eucalyptus species that are abundantly available have low natural durability and poor resistance to fire. These same species are also extremely difficult to treat with preservatives or fire retardants using conventional pressure treatment methods due to a large proportion of refractory heartwood. The aim of this research was to understand whether thermo-mechanical densification had any beneficial effects on the durability or fire performance of plantation Eucalyptus nitens and regrowth Eucalyptus obliqua. Moisture uptake, mass loss and swelling of the samples after exposure to brown and white rot fungi (F. ostreiformis and P. coccineus) were used to analyse the decay resistance of the densified material, while cone calorimeter tests were used to indicate heat release rates. Thermo-mechanical densification has many positive attributes for improving hardness and modifying colour but did not improve decay resistance or fire performance of the samples, however further testing is advised.
B Hassan, J J Morrell, F Wiesner, W Wu, B Belleville, K C Wood