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Water interactions in wood polyesterified with sorbitol and citric acid
2020 - IRG/WP 20-40888
Polyesterifcation of wood with sorbitol and citric acid seems to be a promising chemical wood modification technique that is both low-cost and produced from bio-based chemicals. An interesting aspect of the modification is the interaction of water with the polyesterified wood since the relationship with moisture appears to be unique compared to other wood modification systems. This communication paper presents preliminary results from trials assessing the effect of weight percentage gain (WPG) on swelling properties and water saturated low-field NMR (LFNMR) spectra. Bulking coefficients indicated that the sorbitol-citric acid polymer penetrated the cell wall and higher WPGs led to greater bulking coefficients. Surprisingly, anti-swelling efficiency decreased with increasing WPG. This was due to an increase in water saturated volume at high WPG which suggests the modification alters the structure of the cell wall in a way that allows it to swell beyond its original volume. LFNMR spectra showed the development of a new peak with increasing WPG which may be attributed to water associated with the hydrophilic sorbitol-citric acid polymer.
G Beck, A Treu, E Larnøy

Solvent drying and preservation of timber
1977 - IRG/WP 381
Processes which combine drying and preservation are first reviewed. Some preliminary experiments are then described in which blocks of green Sitka spruce sapwood were immersed, in a solution of tributyltin oxide (TBTO) in methanol at 60°C. Satisfactory penetration of the preservative and exchange of methanol and water occurred in a few hours. The methanol was removed rapidly from the wood by evaporation. Satisfactory penetration of TBTO into initially methanol-saturated samples occurred in a similar period. The factors influencing. such treatments are discussed. High initial moisture content of the wood and a high operating temperature are particularly desirable. Some aspects of the possible commercial operation of the process are discussed.
J A Petty

Diffusion into and bulking of the wood cell wall with polystyrene glycols (PEG)
1991 - IRG/WP 3660
The diffusion and equilibrium distribution of polyethylene glycol (PEG) in the cell walls of red pine (Pinus resinosa) and trembling aspen (Populus tremuloides) were followed by analysing the free lumen solution concentration of vacuum treated wafers at various times after treatment. PEG was more-or-less excluded from the cell walls of wood, depending on the wood species and PEG molecular weight. However, the wood was bulked to a high extent, even with high molecular weight PEG. In aspen, Anti-Shrink-Efficiencies (ASE) of 66, 70, 66 and 58% were achieved with 20% solutions of PEG with nominal molecular weights of 200, 1000, 3350 and 8000 respectively.
P A Cooper, Y T Ung, D Alexander, C Holzscherer

Kd values of Cu, Cr, As in different soil matrix
2007 - IRG/WP 07-50247
Chromated copper arsenate (CCA), a long history of successful preservative, have raised environmental concerns. Adsorption characteristics of domestic soils for chromium, copper, and arsenic were assessed by measuring distribution coefficient (Kd) values of these metal components. The results revealed that Kd values were higher in chromium, followed by arsenic and copper in soil matrix. Different soil matrixes resulted in varying mobilities of CCA components. The values of Kd for all three metals increased with organic matter contents. The results suggest that the mobility of metal components may be very limited to the surface area adjacent to CCA-treated wood due to their fairly large distribution coefficient (Kd). However, the metal components would be persistent and accumulated in the soil, resulting in high chemical concentration in service area of treated wood.
Sung-Mo Kang, Seung-Hun Shin, Ja-Oon Koo

Protection mechanisms of modified wood against decay by white and brown rot fungi
2010 - IRG/WP 10-10713
The resistance of beech and pine wood blocks treated with 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU) against T. versicolor and C. puteana increased with increasing WPG. Full protection (mass loss below 3%) was reached at WPGs of approximately 15% (beech) and 10% (pine). Metabolic activity of the fungi in the wood blocks was assessed as heat or energy production determined by isothermal micro-calorimetry. Fungal activity in the wood decreased with increasing WPG. Still, activity was detected even in wood blocks of highest WPG and showed that the treatment was not toxic to the fungi. The infiltration of untreated and DMDHEU-treated wood blocks with nutrients and thiamine prior to fungal incubation did not result in an increased mass loss caused by the fungi. This shows that the destruction or removal of nutrients and vitamins during the modification process has no influence on fungal decay. In order to study the effect of cell wall bulking and increased surface area, the cell wall integrity was partly destroyed by milling and the decay of the fine wood flour was compared to that of wood mini-blocks. The mass losses caused by the fungi, however, also decreased with increasing WPG and showed comparable patterns like in the case of mini-blocks.To study the effect of the chemical change of cell wall polymers, cellulose was treated with DMDHEU and the product was subjected to hydrolysis by a cellulase preparation. The release of sugar during the incubation was clearly reduced as compared to untreated cellulose. Pre-treatment of modified cellulose with Fenton’s reagent increased the amount of released sugar due to the cellulase activity. Pine micro-veneers were subjected to Fenton’s reagents in acetate buffer over 48h. While untreated specimens and veneers treated with low DMDHEU concentration displayed strong and steady tensile strength loss, veneers treated to a higher WPG did hardly show tensile strength loss.
C Mai, P Verma, Yanjun Xie, J Dyckmans, H Militz

The effects of impregnation with secondary metabolite extracted from Ipe on durability of Japanese cedar and beech wood
2013 - IRG/WP 13-30618
Ipe wood is known for its high durability; it has been widely used in exterior structures that are exposed to the weather. In this paper, to increase the durability of less durable wood, Japanese cedar and beech specimens were impregnated with a secondary metabolite from Ipe. In a previous study, secondary metabolites extracted by a Soxhlet extraction method showed antifungal properties. Therefore, to establish a simpler and more economical extraction method, we investigated extraction by soaking with a solvent. Then, non-durable wood specimens were impregnated with extractives and examined by accelerated fungal tests. After exposure to fungal attack with wood-decaying fungi such as Fomitopsis palustris, Japanese cedar specimens exhibited less than 3% mass losses. Extractives retention after weathering treatment of Japanese cedar and beech specimens were 86.1% and 59.1%, respectively. Moreover, both specimens demonstrated bulk coefficients that suggested the permeation of extractives into cell walls. These results indicated that the extractives of Ipe have high compatibility with cell walls of other types of wood, and can transfer durability against wood-decaying fungi.
T Iida, R Konuma, K Kawarada

Effect of silver nanoparticles on the rate of heat transfer to the core of the medium-density fiberboard mat
2014 - IRG/WP 14-40653
Effect of silver nanoparticles on the rate of heat transferred to the core section of medium-density fiberboard (MDF) mat was studied here. A 400 ppm aqueous nanosilver suspension was used at three consumption levels of 100, 150, and 200 mL/kg based on the weight of dry wood fibers; the results were then compared with the control MDF panels. The size range of silver nanoparticles was 30-80 nm. Results showed that the uniform and even dispersion of nanoparticles throughout the MDF-matrix significantly contributed to the faster transfer of heat to the core section. As to the loss of mat water content after the first 3 – 4 minutes under the hot press, the core temperature slightly decreased in the control panels. However, heat-transferring property of silver nanoparticles contributed in keeping the core temperature rather constant in the NS150 and 200 treatments. As to the de-polymerization of part of the resin in the surface layers of the mat due to the rapid absorption of heat from hot plates by the nanoparticles, it can be concluded that the optimum nano-suspension content should not necessarily be the highest one.
H Reza Taghiyari, O Schmidt, E Bari, P M Tahir, A Karimi, P Nouri, A Jahangiri

Improving dimensional stability of thermally treated wood by secondary modification – potential and limitations
2014 - IRG/WP 14-40664
The potential of treating thermally modified wood with melamine resin to improve the dimensional stabilization is tested in this research. Two different boards of poplar (Populus ssp.) were cut into two halves. One half of each board was thermally modified (T1 and T2) in a commercial process, the other half was used as untreated reference material. The material was thermally modified using the vacu³ process under vacuum and maximum temperatures of 210 °C and 230 °C. Ten samples of each material were impregnated with a solution of a commercially available methyloated melamine resin and dry-cured in a laboratory oven at a maximum temperature of 120°C. The anti-swell-efficiency (ASE) based on the swell rate was tested during ten cycles of repeated drying and wetting. The melamine treatment caused a higher bulking in the references than in thermally modified wood. The ASE of T1 was improved by secondary modification, whereas the ASE of T2 remained higher than that of the secondary modified material. The melamine treatment of thermally modified poplar yielded good results for solution uptake and weight percent gain, but the bulking was lower than expected. Reasons may be found in the same mechanisms providing good dimensional stability of thermally modified wood in the first place: The cell walls are more inaccessible for melamine oligomers due to hydrophobation resulting from thermal modification.
G Behr, K-C Mahnert, S Bollmus, H Militz

Increasing the hardness of wood-composite panels by nanosilver
2016 - IRG/WP 16-40715
Effect of silver nanoparticles on hardness in medium-density fiberboard (MDF) was studied here. A 400 ppm aqueous nanosilver suspension was used at three consumption levels of 100, 150, and 200 mL/kg, based on the dry weight of wood fibers; the results were then compared with the control panels. The size range of silver nanoparticles was 30-80 nm. Composite mats were hot-pressed for 6, 8, and 10 min. Results showed that the uniform and even dispersion of nanoparticles throughout the MDF-matrix significantly contributed to an increase in the hardness at lower hot-press time of 6 min. In the longer hot-press times, however, over-heating of the mat resulted in significant a decrease of hardness values. Significant high correlation was observed between water absorption and thickness swelling.
H R Taghiyari, J Norton, K Heidarhaee

Effects of heat treatment on sound absorption coefficients in nanosilver-impregnated and normal solid woods
2017 - IRG/WP 17-40770
Effects of impregnation with silver nano-suspension as well as heat-treatment on sound absorption coefficients (AC) were studied in tangential direction of five different solid woods based on their importance. AC was measured at two frequencies of 250 and 500 Hz. A 400 ppm nanosuspension was used for the impregnation; silver nanoparticles had a size range of 30-80 nm. Based on the obtained results, the species reacted significantly different in absorbing sound at the two frequencies. Impregnation with nano-suspension substantially decreased AC at the lower frequency of 250 Hz; it did not show any particular trend when AC was measured at the frequency of 500 Hz. Heat treatment significantly increased AC at the frequency of 250 Hz. ACs of mulberry tended to be similar at the two frequencies; in the other four species though, ACs were significantly different. High significant correlations were found in the hardwoods between the ACs measured at the two frequencies.
A Esmailpour, J Norton, H R Taghiyari, H Zolfaghari, S Asadi

Analysis of Wood Industrial Pollutants Based on Emission Coefficients
2017 - IRG/WP 17-50325
Accurate calculation and estimation pollutants is one of the basic tasks of environmental protection .The low carbon economy put forward However,low carbon economy data of wood industry is lack. The paper research on emissions and pollution of Chinese wood industry. The results showed dust emissions from much to least is: fiberboard, plywood and particle board; the amount of industrial waste gas and chemical oxygen demand (COD) in fiberboard are higher than that of plywood and particle board; By comparing the pollutant index change from 2007 to 2013, it is concluded that industrial waste water discharge amount proportion increase rapidly, the average increase for more than 5 times; dust as well as the COD and industrial waste gas by more than two times, and COD has less growth. In this study, the data of energy consumption and pollution emission based on LCA will provide for low carbon development of the wood industry in the world.
Chu Jie, Ma Ji, Zhangjing Chen

Hydrolytic stabilization of chemically modified Bambusa vulgaris Shrad ex JC Wendl
2018 - IRG/WP 18-40830
The main drawback which greatly limit the utilisation of bamboos is their high moisture intake, biodegradation and physical properties changes with environmental variations. To prevent excessive dimensional changes and improve moisture properties of bamboo, Bambusa vulgaris was chemically treated with acetic-anhydride without co-solvent. To evaluate the influence of acetylation on the moisture properties. The weight gain (WPG), Bulking coefficient (BC), Rate of reaction (RR), Volumetric Swelling (VS) and Anti-swelling Efficiency as well as changes in VS and ASE upon long term water soaking and weight loss to leaching (WL) were determined. The results indicated no significant effect of reaction temperature and time on the WPG, BC, VS and ASE of the acetylated bamboo while reaction time had significant influence on RR and WL. None of the bamboo samples had more than 3.67% WPG and 54.69 % ASE. The maximum values of ASE of acetylated bamboo was 54.69% at 2.785 WPG while the lowest 13.08% was recorded at 2.89% WPG. However, at the lowest WPG of 1.61 %, ASE of 35.88% was recorded while the highest WPG of 3.67% gave ASE of 32.84 %. ASE varied from 13.08 % to 54.69% the lowest being recorded at 140oC, 30 mins reaction time while the highest (54.69%) was recorded at 100oC, 90 minutes reaction time. Temperature had no influence on the initial and final volumetric swelling and final anti-swelling efficiency of the modified bamboo samples but reaction time had significant effect on initial ASE. Volumetric swelling of modified samples increased from 8.47 to 18.58% while the unmodified samples swelled from 9.42% to 43.22% within 7 days water soaking period. Acetic anhydride form chemical bonds that are stable to solvent extraction in B. vulgaris. Acetylating at 120°C for 30 and 60 minutes is suitable for B. vulgaris to positively influence its sorption properties.
N A Sadiku, S M Akintayo

Thermally modified timber treated with methacrylate
2018 - IRG/WP 18-40849
Thermally modified timber (TMT) from Scots pine sapwood similar to Thermo-D quality was impregnated with methacrylate resin by the hot-and-cold method and subsequently cured at elevated temperatures. The results showed that methacrylate resin could be used to reduce colouring of painted TMT wood during accelerated weathering probably by hindering the migration of extractives. The resin itself did not reduce greying of the unpainted wood. Hardness was only slightly improved by treatment with the resin probably due to a higher density of the material. Formation of blisters occurred but was reduced by treatment with the resin. Resistance to mould growth by a mixture of Aureobasidium pullulans, Cladosporium cladosporioides, Aspergillus versicolor, Penicillium purpurogenum was performed by applying EN-15457:2014. Treatment with methacrylic resin hindered the colonisation of the three last mould fungi.
O Karlsson, O Myronycheva, DJones, D Elustondo, D Sandberg