Die Verbesserung der Impraegnierbarkeit von Fichtenholz mittels chemischer und enzymatischer Vorbehandlung

Finely ground spruce ( Picea abies (L.) Karst. ) was incubated with different enzyme preparations. The enzyme concentration, incubation time, temperature and buffer concentration were varied. The nature and quantity of uronic acids and neutral sugars released from the cell walls were determined. The most effective enzyme preparations were shown to be those with a broad cellulolytic and hemicellulolytic spectrum of activity. Specific pectinases were found not to be particularly effective. Sapwood and heartwood were broken down in equal degrees. Enzymatic preliminary treatment of intact spruce improved the permeability of the timber. The extent of the improvement was dependent on the enzyme preparation applied, the enzyme concentration, the incubation time, the incubation temperature and the origin of the timber. Enzymatic preliminary treatment was more effective in sapwood than in heartwood. Scanning electron microscopy made it possible to demonstrate the decomposition of the torus and the margo of the bordered pits as well as the decomposition of the pits between tracheids and parenchyma. The compression strength and the modulus of elasticity were not reduced. Preliminary treatment of intact spruce with alkali, acids and chelating agents did not result in improved permeability

Termite resistance of DMDHEU-treated wood.

Four field trials were conducted with wood modified with dimethyloldihydroxy-ethyleneurea (DMDHEU) in contact with subterranean termites. Trials 1 to 3 were conducted with Coptotermes acinaciformis (Froggatt); 1 and 2 in south-east Queensland, and 3 in northern Queensland, Australia. Trial 4 was conducted in northern Queensland with Mastotermes darwiniensis (Froggatt). Four timber species (Scots pine, beech, Slash pine and Spotted gum) and two levels (1.3 M and 2.3 M) of DMDHEU were used. The tests were validated. DMDHEU successfully prevented damage by C. acinaciformis in south-east Queensland, but not in northern Queensland. It also did not protect the wood against M. darwiniensis. Except for beech in trial 4, DMDHEU led to reduced mass losses caused by termite attack compared to the unmodified feeder stakes. Slash pine (in trials 1 and 3) and Spotted gum (in trial 1) presented low mass losses. Modification of Scots pine was more effective against termite damage than the modification of beech

ДИНАМІЧНИЙ МОДУЛЬ ПРУЖНОСТІ ХВИЛЯСТО-ЗАВИЛЬКУВАТОЇ ДЕРЕВИНИ ABIES ALBA MILL.

To get deeper knowledge of wood quality as a practical stage of wood grading, which plays an engineering role in wooden construction and production of structural timber, dynamic module of elasticity of wave-grained wood was investigated. The main objective was focused on testing of Silver fir wood with straight-grained and wave-grained structures within stem radius and height. Altogether, 12 model trees were selected in the forest stand of Bukovyna Carpathians with geographical location of latitude of 48о06ʹ02.34ʺ N, longitude of 25о13ʹ02.46ʺ E and altitude of 985 m asl. Dynamic modulus of elasticity was defined on the Grindo Sonic device of the Department of Wood Biology and Wood Products of Georg-August-Universität Göttingen, Germany within the framework of COST Action FP1407: ModWoodLife. The differences of dynamic modulus of elasticity, damping coefficient and sound velocity between wave-grained and straight-grained wood of Silver fir were estimated. The variation of studied parameters within stem radius and height was graphically analysed. In the stems with wavy-grained wood structure, two wood quality classes were proposed, namely: the first one involved peripheral wood (40 % of the stem radius) and the second one ‒ the central (heart) wood. Wood damping varied from 6 to 10 for wavy-grained wood, and from 12 to 14 for straight-grained wood. The linear relationship between dynamic modulus of elasticity and wood density was estimated. Increasing of wood density caused an increase of the dynamic modulus of elasticity and was described by the linear equation of the first order (R²=0.69…0.72). The linear relationship between wood density and dynamic modulus of elasticity of wavy-grained wood was inversely proportional. The dynamic modulus of elasticity of straight-grained wood ranged from 5921 to 12995 Н∙mm-2, and wavy-grained wood ‒ 5053 to 12393 Н∙mm-2.Досліджено відмінності динамічного модуля пружності, коефіцієнта затухання та швидкості звуку хвилясто-завилькуватої деревини порівняно з прямоволокнистою деревиною ялиці білої. Графічно наведено варіацію досліджуваних показників у межах радіуса та висоти стовбура. У межах радіуса стовбура із хвилясто-завилькуватою структурою можна виділити два класи якості деревини, а саме: перший – периферійна деревина (40 % радіуса стовбура) та другий – центральна (ядрова) деревини. Структурне розміщення деревного волокна, зокрема хвилясто-завилькувате, істотно визначає фізико-механічні характеристики деревини та їх варіацію. Коефіцієнт затухання деревини змінюється: від 6 до 10 для хвилясто-завилькуватої деревини; від 12 до 14 для прямоволокнистої деревини. Встановлено прямолінійну залежність першого порядку між динамічним модулем пружності та об'ємною масою деревини. Збільшення об'ємної маси прямоволокнистої деревини зумовлює збільшення модуля пружності та описується рівнянням прямої (R²=0,69…0,72). Прямолінійна залежність між динамічним модулем пружності та щільністю хвилясто-завилькуватої деревини є інверсійною. Динамічний модуль пружності прямоволокнистої деревини знаходиться в межах від 5921 до 12995 Н∙мм-2, а хвилясто-завилькуватої деревини – від 5053 до 12393 Н∙мм-2

Evaluation of wooden materials deteriorated by marine wood boring organisms in the black sea

Marine borers can destroy wooden structures exposed to the marine environment and cause great monetary loss. In the region of Amasra of the Black Sea in Turkey, ships continue to be built from wood, mainly Castanea sativa (sweet chestnut) and Quercus petraea (sessile oak) and therefore are subject to destruction by marine borers. Copper-chromium-arsenic (CCA), used to be one of the most common wood preservatives used    in Turkey. However, in this area its efficacy against mari-ne borers is unknown.   The resistance of untreated and CCA-treated samples of chestnut, oak and Scots pine (Pinus sylvestris) was examined  and aft er twelve months evaluated in two ways, EN 275, and a non-destructive measurement for dynamic modulus of elasticity (MOE). Untreated samples, particularly Scots pine were severely attacked by Teredo navalis. Treated samples of oak and chestnut were moderately attacked while treated samples of Scots pine sapwood and heartwood were sound. Severity of wood boring attack determined using MOE showed a very good correlation with that de-termined by visual assessment in untreated wood, and a good correlation for treated wood. Dynamic MOE allows rapid on-site evaluation rather than measurements within a laboratory and also without causing damage to the structures being evaluated

Determination of fungal activity in modified wood by means of micro-calorimetry and determination of total esterase activity

Beech and pine wood blocks were treated with 1,3-dimethylol-4,5-dihydroxyethylen urea (DMDHEU) to increasing weight percent gains (WPG). The resistance of the treated specimens against Trametes versicolor and Coniophora puteana, determined as mass loss, increased with increasing WPG of DMDHEU. Metabolic activity of the fungi in the wood blocks was assessed as total esterase activity (TEA) based on the hydrolysis of fluorescein diacetate and as heat or energy production determined by isothermal micro-calorimetry. Both methods revealed that the fungal activity was related with the WPG and the mass loss caused by the fungi. Still, fungal activity was detected even in wood blocks of the highest WPG and showed that the treatment was not toxic to the fungi. Energy production showed a higher consistency with the mass loss after decay than TEA; higher mass loss was more stringently reflected by higher heat production rate. Heat production did not proceed linearly, possibly due to the inhibition of fungal activity by an excess of carbon dioxide

Microstructural and physical aspects of heat treated wood. Part 2. Hardwoods

Heat treatment of wood is an effective method to improve the dimensional stability and durability against biodegradation. Optimisation of a two-stage heat treatment process at relatively mild conditions (<200° C) and its effect on the anatomical structure of hardwoods were investigated by means of a light and scanning electron microscopic analysis. Hardwood species such as beech and poplar, were predominantly sensitive to collaps of the vessels and some deformation of the libriform fibres directly near the vessels. In treated beech and birch radial cracks were observed near the rays. Optimisation of the heat treatment process conditions including the application of a steam hydro thermolysis stage reduced such damages to a minimum. Broken cell walls perpendicular to the fibre direction resulting in transverse ruptures has been noticed in heat treated hardwood species. This contributes to abrupt fractures of treated wood as observed in bending tests which can lead to considerably different failure behavior after impact of mechanical stress. In some treated hardwood species maceration (small cracks between tracheids) was noticed after heat treatment. Heat treatment did not reveal damage to the ray parenchyma pit membranes, bordered pits and large window pit membranes; and the margo fibrils appeared without damage

Microstructural and physical aspects of heat treated wood. Part 1. Softwoods

Heat treatment of wood is an effective method to improve the dimensional stability and durability against biodegradation. Optimisation of a two-stage heat treatment process at relatively mild conditions (<200° C) and its effect on the anatomical structure of softwoods were investigated by means of a light and scanning electron microscopic analysis. Heat treatment did have an effect on the anatomical structure of wood, although this depends on the wood species considered and on the process method and conditions used. Softwood species with narrow annual rings and/or an abrupt transition from earlywood into latewood were sensitive to tangential cracks in the latewood section. Radial cracks occurred mainly in impermeable wood species such as Norway spruce, caused by large stresses in the wood structure during treatment. Sapwood of treated pine species revealed some damage to parenchyma cells in the rays and epithelial cells around resin canals, whereas this phenomenon has not been noticed in the heartwood section. Treated radiata pine resulted in a very open and permeable wood structure limiting the applications of this species. Broken cell walls perpendicular to the fibre direction resulting in transverse ruptures have been noticed in treated softwood species. This contributes to abrupt fractures of treated wood as observed in bending tests which can lead to considerably different failure behavior after impact or mechanical stress. In some treated softwood species maceration (small cracks between tracheids) was noticed after heat treatment. Heat treatment did not cause damage to the ray parenchyma pit membranes, bordered pits and large window pit membranes; the margo fibrils appeared without damage. Compared to the other softwood timbers tested European grown Douglas fir was the timber that stands heat treatment the best