Untersuchungen zur Permeabilität von Faser-, Span- und OSB-Matten für Gase

After an explanation of the importance of mat permeability during wood-based panel manufacture the relevant literature is reviewed. Preparation of specimens and gas-permeability measurement methods are described. Darcy’s law can be applied to describe the gas flow in wood-based panel mats under the influence of a pressure gradient during the hot pressing process. The permeability parallel to the panel surface influences the rate of venting. The transverse permeability is important for the convective transfer of heat and moisture into the core layer. The permeability of fibre, particle and strand mats with densities varying from 200 to 1200 kg/m³ was determined. At lower densities, the parallel and transverse permeability of fibre mats and the transverse permeability of OSB mats are distinctly lower than the permeability of particle mats. Particle mats made from surface material are less permeable than those made from core material. At higher densities, fibre mats reveal highest permeability followed by surface and core layer particle mats and strand material. At higher densities, mat permeability decreases with increasing glue and moisture contents. The pressing temperature and the accompanying plastizisation of the mats does not influence the permeability.     

Untersuchungen zur Quellung und Wärmedehnung von Faser-, Span- und Sperrholzplatten

The swelling in plane and perpendicular to the plane as well as the thermal expansion in plane of diverse wooden materials (fibreboard, particle board, plywood) were investigated. A strongly reduced differential swelling of between 80% and 95% relative humidity in relation to the swelling of between 35% and 80% relative humidity was observed by all wooden materials which were investigated. The swelling also depended on the density within the diverse materials (plywood and particle boards). The different swelling of plywood parallel and perpendicular to the fibre of the face veneer depended strongly on the layer that was measured (⊥ or ||). The swelling perpendicular to the plane of the diverse particleboards depended on the density. With plywood, the swelling perpendicular to the plane was similar to the tangential swelling of solid wood, although the veneers are oriented radially in this direction. This can be explained by the mechanically restrained swelling in plane due to the adjacent plies. In all wooden materials the thermal expansion is very low (3.7 to 5.9· 10^-6 m/(m·K)). Plywood had the lowest thermal expansion and is similar to the value of solid wood in the longitudinal direction. The thermal expansion of particleboard and fibreboard is 1.5 fold higher than that of plywood.     

Vergleichende Untersuchungen zum thermischen Verhalten von Maisproteinen 2. Mitt. Untersuchungen an Prolamin und Glutelin des Maises

Comparative investigations on thermic reactions of maize proteins. Part 2. Investigations on prolamin and glutelin of maize Zein and Glutelin show in comparison to outgoing values a decrease in protein solubility, most probably due to cross-linking reactions, as proved by SDS-polyacrylamid-gelelectrophoresis investigation. The addition of D-glucose to the reaction-system increases the degree of aggregation due to nonenzymatic browning. This cross-linking reaction takes place in conjunction with decrease in glutamine, lysine and arginine amino acid residues of the investigated proteins.     

Untersuchungen zum Verhalten des Splint- und Kernholzes der Pappel bei der Herstellung von Zellstoffen

Poplar heartwood and sapwood of the clones of Muhle-Larsen and Oxford show distinct differences in fibre length and chemical properties. NSSC-pulps from sapwood are of higher degree of whiteness and tear resistance but of lower yield compared to heartwood pulps; however, no significant differences in the tensile and burst strength were observed between NSSC-pulps of heart- and sapwood. Strength properties of sulphate pulps prepared from both heart- and sapwood were significantly influenced by pulping conditions. Heartwood pulps are generally of higher yield and ash content than those made from sapwood. Definite differences in the degree of whiteness as well as in the strength properties between heart- and sapwood pulps were detected. Moreover, clonedependent differences in the properties of pulps from heart- and sapwood do exist.     

Untersuchungen zum Sorptions- und Quellungsverhalten von thermisch behandeltem Holz

Zusammenfassung Proben aus Radiata pine (Pinus radiata D. Don), Douglasie (Pseudotsuga menziesii Franco), Laurel (Laurelia sempervirens (R. et Pav.)Tul), Edelkastanie (Castanea sativa Mill.) und Eiche (Quercus robur L.) wurden im belüfteten Trockenschrank jeweils 24 h bei 100°C, 150°C bzw. 200°C) wärmebehandelt. Danach wurden das Sorptionsverhalten bei variabler Luftfeuchte und die Quellung in radialer und tangentialer Richtung bestimmt. Als Bezugsbasis dienten unbehandelte Proben. Je Variante wurden zehn Proben verwendet. Das Sorptionsverhalten wurde basierend auf den gemessenen Werten mit dem Hailwood–Horrobin-Modell berechnet. Je nach Holzart kam es bereits ab 100°C teilweise zu einer merklichen Reduzierung der Gleichgewichtsfeuchte. Bei 150°C und insbesondere bei 200°C war eine deutliche Reduzierung der Gleichgewichtsfeuchte und Quellung vorhanden. Mit dem HH-Modell konnte nachgewiesen werden, dass es dabei sowohl zu Änderungen der Porenstruktur als auch der Chemisorption kommt. Auch die Verkettung der Cellulosemoleküle ändert sich. Der Unterschied zwischen tangentialer und radialen differentialer Quellung steigt in der Reihenfolge Pinus radiata, P. menziesii, C. sativa, L. sempervirens und Q. robur. Die tangentiale differentielle Quellung ist allgemein empfindlicher auf die Wärmebehandlung als die radiale. Was die tangentiale differentielle Quellung anbelangt setzt sich Q. robur von den übrigen untersuchten Holzarten in den absoluten Werten deutlich ab. Mit Ausnahme von Pinus radiata tendiert der Anisotropie-Koeffizient bei 200°C dazu, leicht abzunehmen. Die Dichte sank bei allen Holzarten durch die Behandlung ab.

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Investigations on the sorption and swelling properties of thermally treated wood

Samples from Pinus radiata D. Don, Pseudotsuga menziesii Franco, Laurelia sempervirens (R. et Pav) Tul., Castanea sativa Mill. and Quercus robur L. were heat treated under air condition in each case during 24 h at 100°C, 150°C and 200°C. The sorption behaviour and swelling (tangential and radial) were examined in the hygroscopic range between RH 11% and 93% with untreated speciments as reference basis. For each variant ten samples were used. The sorption analysis was performed using the Hailwood–Horrobin sorption model. Depending on wood species, already starting with 100°C, a noticeable reduction of the equilibrium moisture content was observed. At 150°C and particularly at 200°C a distinct reduction of the equilibrium moisture content was measured. The sorption analysis according to the Hailwood–Horrobin model showed that changes in the void structure and chemisorption occurred. Also cross linking between cellulose molecules takes place. The difference between tangential and radial differential swelling increases in the order Pinus radiata, P. menziesii, C. sativa, L. sempervirens and Q. robur. The tangential differential swelling is generally more sensitive to thermal treatment than the radial swelling. The absolute swelling values of Q. robur are significantly higher than the values of the other wood species under study. With the exception of Pinus radiata the anisotropy coefficient tends to decrease slightly at 200°C. In all the examined wood species the heat treatment caused a decrease in density.

     

Zum Recycling von Span- und MDF-Platten

In part 1 of the work (Franke and Roffael 1998) investigations were carried out on the influence of thermal hydrolysis of UF-bonded particle- and medium density fibreboards (MDF). The degradation of UF-resins was followed up, the change of the pH-value in the water extractives, the yield and the pentosan content of the lignocellulosic material were also assessed. Due to thermal hydrolysis the pH-value of water extractives increases and their alkaline buffering capacity decreases? Moreover, it was shown that UF-resins have a relatively high resistance towards hydrolysis. In this part of the work investigations were conducted on the formaldehyde release at different test temperatures. Further, the influence of thermal treatment of the disintegrated baords on the ammonia release was assessed. Moreover, the change of the pH-value of the extractives was determined. For comparison particles from round pinewood were included in the investigation.     

Beitrag zum unterschiedlichen mikroskopischen Verhalten von Mark- und Schalerbsenst?rke

Zusammenfassung Es wird über das unterschiedliche mikroskopische Verhalten der Stärke der Schalund Markerbse berichtet. Die beiden Stärken weisen sowohl Unterschiede zwischen gekreuzten Polarisatoren als auch im Quellungsbereich und gegenüber Diastase auf. Während die Stärkekörner der Schalerbse eine gute Doppelbrechung geben, von Diastase abgebaut werden und sich der Quellungsbereich eindeutig bestimmen läßt, zeigen die Stärkekörner der Markerbse nur eine schwache Doppelbrechung, sind resistent gegenüber Diastase und der Quellungsbeginn und das -ende lassen sich schwerer bestimmen. Die Ergebnisse werden eingehend diskutiert.     

Untersuchungen zum Kriechverhalten von MDF und Spanplatten im Normalklima

Ohne Zusammenfassung     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

Zusammenfassung: In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden. Vibrio spp. konnte mit 60 Isolaten in 49 Proben (44%) nachgewiesen werden. Am h?ufigsten wurde Vibrio cholerae non-O1 non-O139 isoliert (n=34). Aus 14 Proben konnte Vibrio parahaemolyticus isoliert werden und in fünf Proben konnte Vibrio vulnificusnachgewiesen werden. Erstmals konnte Norovirus in Garnelen nachgewiesen werden. 21 (18,9%) der untersuchten Proben waren positiv. Sowohl Rotavirus als auch Hepatitis A-Virus konnten hingegen nicht nachgewiesen werden.

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In this study 111 samples of raw imported aqua-cultured shrimps have been examined for bacterial pathogens and for pathogen viruses. The samples originated from South-East Asia except for eight Latin-American samples. Most samples were taken from Bangladesh (n=40). The bacteriological quality of these samples was analysed in terms of aerobic plate count, Escherichia coli, Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Vibrio species. Rotavirus, norovirus and hepatitis A-Virus were detected by using a nested RT-PCR. The aerobic plate count was found to be in a range between 4,8×10² to 1,3×10⁹ cfu/g. Fourteen samples (12,6%) showed an aerobic plate count >10⁷ cfu/g. One sample was found to be contaminated with Escherichia coli at a level of 1,9×10³ cfu/g. Staphylococcus aureus was isolated from sixteen samples. Listeria monocytogenes was not detected in any of the shrimp samples examined. Salmonella spp. was found in eight samples. Salmonella Weltevreden was the most frequently isolated serovar. Forty-nine shrimp samples (44%) were positive for Vibrio spp. and 60 Vibrio-isolates could be extracted. Vibrio cholerae non- O1 non-O139 was isolated in 34 samples as the most frequent species. 14 samples contained Vibrio parahaemolyticus, Vibrio vulnificus was present in five samples. For the first time Norovirus could be detected in shrimps. 21 (18,9%) of all examined samples were positive. However, both rotavirus and hepatitis A-virus could not be detected.

Eingegangen: 21. November 2007     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden.     

Orientierende Untersuchungen zum Verhalten des Splint- und Kernholzes der Pappel bei der Zementbindung

Heart- and sapwood of poplar wood show different chemical properties, which affect their behaviour towards cement bonding. Water extractives of sapwood show a lower pH value and a higher puffering capacity towards alkali. Moreover, the content of water soluble carbohydrates is higher in sapwood than in heartwood Water extractives of sapwood delay the hydration of cement to a higher extent than those of heartwood. Differences related to the clone type have been also detected. Cement composites made from sapwood were, however, generally of higher strength properties than those made of heartwood. The difference in strength properties is still remarkable even after 8 weeks of storage. The pH value and puffering capacity of the composites made from sap-and heartwood showed no significant differences.     

Vergleichende Untersuchungen zum thermischen Verhalten von Maisproteinen 1. Mitt. Modelluntersuchungen an Maisalbumin

Comparative investigations on thermic reactions of maize proteins. Part 1. Model investigations on maize albumin Using a modelprotein (maize albumin) the influence of thermal process and interchanges with carbohydrates, especially D-glucose, were investigated. These reactions are combined with high losses of the amino acids lysine, arginine and proline and as such as asparagine and glutamine. The results show the formation of high molecular protein structures in the heated samples together with a decrease of subfractiones under 20 kD molecular weight, this being probably due to protein/protein and/or protein/D-glucose thermal aggregation.