Systematische Untersuchungen der Wirkung aggressiver Gase auf Fichtenholz

In extension of previously described chemical investigations on spruce wood treated with formaldehyde, ammonia, sulfur dioxide and chlorine, sorption experiments were made applying the same gases. The wood samples treated with gases were also tested in bending stress. Wood absorbs ammonia very quickly, but the gas is only slightly bound. The absorption of chlorine takes place only slowly, but chlorine is almost completely bound. In contrast to NH₃ and Cl₂ more SO₂ is absorbed with increasing moisture of wood. While treatments with formaldehyde and NH₃ cause an increase of wood strength, treatment with SO₂ causes a minor, treatment with Cl₂ a deep drop in strength respectively. All results of the chemical and physical investigations are finally compiled in a schedule giving an estimate of the effects of aggressive gases on spruce wood.     

Systematische Untersuchungen der Wirkung aggressiver Gase auf Fichtenholz

Samples of spruce wood treated with formaldehyde, ammonia, sulphur dioxide and chlorine for a longer time were studied in the scanning and transmission electron microscope. Samples derived from formaldehyde and NH₃ treatments show only minor changes in the compound middle lamella and S1. The treatment with SO₂ causes losses of substance across the whole cell wall. Severe changes in the form of loosening of the cell wall structure and fissures in the cell wall can be seen after a treatment with chlorine. In all cases the compound middle lamellae and the tissue structure remain. Loading of the wood samples during NH₃ treatment distorts the cell walls in the zone of pressure; during treatment with SO₂ and Cl₂ the cell walls break and rend in the zone of pressure.     

Systematische Untersuchungen der Wirkung aggressive Gase auf Fichtenholz

The investigations' objective was to give information about the chemical and structural changes in wood, caused by the influence of various aggressive gases. Small rods of sprucewood with different wood moisture contents were treated with formaldehyde, ammonia, sulphur dioxide, and chlorine over a period of 336 days. Decomposition products were removed in three extraction steps (water, ethanol-benzene, alkali), followed by the analyses of the extracts and the extracted wood residues. The present results reveal that wood is decomposed only slightly by formaldehyde and ammonia. The decomposition by sulphur dioxide is rather restricted, at least at room temperature. A strong decomposition of the wood components was found after treatment with chlorine.     

Untersuchungen zum Einfluss der thermischen Vergütung auf die Porosität von Fichtenholz

Ohne Zusammenfassung

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Untersuchungen zum Einfluss der thermischen Vergütung auf die Porosität von Fichtenholz

     

Untersuchungen zur Bestimmung der Poissonschen Konstanten an Fichtenholz

On spruce wood, the MOE in all three main directions (longitudinal, radial, tangential) and the six Poisson ratios were determined after climatisation at 20 °C and 65% rel. humidity using an incremental displacement transducer. The ratios of the different MOEs were calculated as E_T:E_R:E_L =1:2.43:25.4. The following Poisson ratios were determined: μ_RL=0.022, μ_TL= 0.015, μ_LR=0.376, μ_LT=0.420, μ_TR= 0.335, μ_RT=0.640.     

Einfluß der Nadelperforation auf die Biegefestigkeit von Fichtenholz

Battens and square timber of the dimensions 50 mm×80 mm up to 100 mm×120 mm made of spruce wood of grades I and II, DIN 4074, were incised to improve their treatability. The strength tests revealed that the bending strength of the different assortments was not reduced.     

Rasterelektronenmikroskopische Untersuchungen an Zugbruchflächen von Fichtenholz

The influence of temperature, wood moisture content, and duration of load on the ultrastructure of tension-fracture surfaces of bending-loaded spruce samples has been investigated by means of a high-resolution SEM with a field-emission cathode (PE-SEM). The main results are: The influence of the loading conditions—especially the load duration—on the tension strength and deformation of the microscopic fracture-surface of the cell tissue and the cell wall is clearly visible. Thus, brittle fractures of the cell wall are significantly distinguishable from ductile fractures. Heat and moisture increase the ductile character of the fracture surface.     

UV-mikroskopische Untersuchungen zur Herkunft des Milled-Wood-Lignins aus Fichtenholz

Ohne Zusammenfassung Mit Unterstützung der Deutschen Forschungsgemeinschaft     

Die Wirkung der Ammoniumpersulfat-Behandlung von Mehl auf den Methioningehalt des Brotes

Ohne Zusammenfassung