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Effect of medium-term degradation of beech wood by erosive (Phanerochaete chrysosporium) and lignin-selective (Ceriporiopsis subvermispora) strains of white rot fungi on its selected physical properties
2004 - IRG/WP 04-40292
At the Faculty of Wood Sciences and Technology a fungal delignification of normal and tension beech wood by erosive and lignin-selective strains white-rot fungi has been studied. The pre-treatment of both kind of wood samples was accompanied by partial delignification and apparent changes of their physical properties influencing the polar liquids penetration.
R Solár, S Kurjatko, M Mamonová, J Hudec


Changed permeability and surface properties of hornbeam wood due to its degradation by erosive strain of Phanerochaete chrysosporium
2004 - IRG/WP 04-40290
Specimens of hornbeam wood were submitted to a medium-term degradations by erosive fungus Phanerochaete chrysosporium. Biodegradations of specimens resulted in their apparent structural alterations, changes in permeability and increased intensity of interactions with polar liquids. Modified physical properties of biodegraded wood may significantly influence its penetration with polar media and chemical pulping
R Solár, S Kurjatko, L Reinprecht, M Mamon, V Vacek


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


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


Mechanistic aspects of the reactions of copper complexes with lignin in the presence of hydrogen peroxide and lipid hydroperoxide model compounds as proposed for white rot fungi
2001 - IRG/WP 01-10399
The structural principles and the oxidative reactions of the catalytic system consisting of copper, hydroperoxides, and copper coordination compounds that contain aromatic nitrogen atoms are similar to those of catalytic centers of oxidative enzymes involved in delignification reactions of white rot fungi. The system is capable of selectively degrading lignin and its low molecular weight would allow to react oxidatively also at sites of the wood cell wall, where enzymes cannot penetrate. Understanding the mechanisms of white rot would offer perspectives to develop targeted wood preservatives to inhibit these enzymatic and non-enzymatic reactions of wood decay. Studies on the mechanism of the copper/pyridine and 4-aminopyridine resp./hydrogen peroxide system that were carried out with 14C-labeled lignin and cellulose model compounds demonstrated the selectivity of the copper system for lignin structures and the ability of the system to oxidise even non-phenolic lignin. Product profiles of the reactions supported by ESR measurements suggested a non-radical reaction pathway involved in that case. However, when a lipid hydroperoxide model (cumene hydroperoxide, CHP) was used as peroxide source, a variety of free radicals derived from this peroxide could be detected in ESR. Selective staining of treated wood sections with safranin and astra blue showed degradation of softwood and hardwood lignin in the middle lamella and secondary cell wall. Besides its importance for developing targeted wood preservatives, the coordinated copper system has great potential for application for selective lignin degradation in the pulp and paper industry and could therefore replace environmentally problematic chlorine and chlorine dioxide based pulp bleaching stages.
K Fackler, P Lamaipis, E Srebotnik, M Humar, C Tavzes, F Pohleven, M Sentjurc, T Watanabe, K Messner


The relationship between preservative type and surface degrade in Pinus radiata
1980 - IRG/WP 3158
Samples of Pinus radiata D. Don were impregnated with one of two preservative types, a copper chrome arsenic salt and a light organic solvent preservative. The panels were exposed to the weather for 4-5 years at a site near Sydney, Australia. Macroscopic and microscopic examinations showed different rates and patterns of weathering between the samples treated with each preservative and an untreated control. The sample treated with copper chrome arsenic salt indicated reduced lignin and cellulose degradation when compared to the untreated wood and the lignin and cellulose breakdown was greatest in the wood impregnated with light organic solvent preservative. Adsorption of copper and chromium onto lignin and cellulose appears to have stabilised the wood treated with copper chrome arsenic salt and the organic solvent preservative appears to have solubilised the lignin and facilitated weathering.
R S Johnstone, R K Bamber


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


Decay resistance of wood-plastic composites reinforced with extracted or delignified wood flour
2014 - IRG/WP 14-40655
The moisture and decay resistance of wood-plastic composites (WPCs) reinforced with extracted or delignified wood flour (WF) was investigated. Three different extractions were preformed: toluene/ethanol (TE), acetone/water (AW), and hot water (HW). Delignification (DL) was performed using a sodium chlorite/acetic acid solution. All WPCs specimens were made with 50% by weight HDPE and WF, first compounded using extrusion followed by injection molding. After preconditioning in water at 70 °C for 5 days, the specimens were exposed for 12 weeks to the brown-rot fungus, Gloeophyllum trabeum in the AWPA D1413 standard soil block test. The WPC made with untreated wood flour had the highest overall weight loss (24.9 ±3.6%), followed by the HW (22.3 ±4.6%) and DL (16.4 ±3%). The TE (7.8 ±0.8%) and AW (7.7 ±2.3%) had the lowest weight losses. WPC moisture content was monitored before and after decay. Cracking was observed in some blends after the preconditioning, which may explain the differences in weight loss.
R E Ibach, Yao Chen, N M Stark, M A Tshabalala, Yongming Fan, Jianmin Gao