Einfluß der Verkernung und des Baumalters auf die Eigenschaften von Spanplatten aus Kiefernholz (Pinus sylvestris)

The biological resistance of particleboards made from sap-and heartwood of Pine (Pinus sylvestris) from trees of different ages was investigated using the brown rot fungi Coniophora puteana. The particleboards were bonded with polymeric diisocyanate (PMDI), melamin-urea-phenolformaldehyde resin (MUPF-resin), phenolformaldehyde resin (PF-resin) and tanninformaldehyde resin (TF-resin). As reference particleboards from sap- and heartwood of Douglas Fir (Pseudotsuga menziesii) and Larch (Larix decidua) were investigated using the binders PMDI, MUPF-, PF- and TF-resin as well as particleboards from sapwood of pine containing a chemical wood preservative. Generally, MUPF- and TF-bonded particleboards made from heartwood were of higher biological resistance compared with those made from sapwood using the same binder system. In case of PMDI-bonded pine particleboards the influence of heartwood on the biological resistance was almost undetectable. TF-bonded particleboards made from heartwood of 126-year-old pine (samples without leaching) showed a very high resistance towards biological attack. Leaching of particleboards prior to testing decreased the biological resistance of TF-bonded pine boards from old trees. The difference between the biological resistance of untreated and leached particleboard samples was especially high in case of TF-bonded particleboards of heartwood from old pine, whereas leaching did not seem to have such effect on the biological resistance of TF-bonded particleboards of young pine and Douglas fir and larch, respectively. The resistance of MUPF- and PMDI-bonded boards remains unaffected by leaching.     

Einfluß der Verkernung und des Baumalters auf die Eigenschaften von Spanplatten aus Kiefernholz (Pinus sylvestris)

Chips from sap- and heartwood of 2-- and 126-year-old pine of the same site were chemically characterized. One-layer boards of 20 mm thickness were prepared from the chips using melamine-urea-phenol-formaldehyde resin (MUPF-resin), phenolformaldehyde resin (PF-resin), tannin-formaldehyde resin (TF-resin) and adhesives based on polymeric diisocyanate (PMDI). The physical and chemical properties of the boards were determined. Moreover, the influence of hot water extractives on the pH-value, viscosity and gelation time of the resins was assessed. The results reveal: Sap- and heartwood chips differ in their chemical properties and bonding behaviour. The age of the tree has also a dominant influence on the bonding characteristics of the chips. The addition of heartwood water extractives to PF- and MUPF-resin decreases the pH value and increases the viscosity, the attained viscosity of the resins remained unchanged for 6 h. In addition, water extractives of heartwood increase significantly the gelation time of TF-resin. Thickness swelling, water absorption and equilibrium moisture content of heartwood boards were always lower irrespective of the binder used than those of the corresponding sapwood boards. Moreover, bending and internal bonding strength of heartwood boards from 40-year-old trees were much higher than those produced from corresponding sapwood. The strength properties of the heartwood boards deteriorate, however, with increasing age of the tree. In addition, MUPF- and TF-bonded boards from heartwood were in general of lower formaldehyde release compared with boards from sapwood. The chemical properties of heart- and sapwood boards depend on the binder and the age of tree.     

Mikrobiologische Untersuchungen an frischem und gelagertem Holz von Bäumen aus Waldschadensgebieten und Prüfung der Pilzresistenz des frischen Holzes

Comparative microbiological investigations on the fresh wood of healthy and diseased Norway spruce trees show an increased occurrence of fungi and bacteria in the diseased trees. However, microorganisms in the wood do not seem to be a causal factor for the spruce decline; they are secondary pathogens which add further stresses to the wakened trees. Experiments on the storage of spruce logs with bark for 6 to 7 months yield a nearly equal attack by staining fungi of the wood of diseased trees as compared to the healthy ones. Decay experiments in Kolle flasks with wood samples of spruce and European beech trees do not show a different decay susceptibility towards wood destroying fungi between the wood of healthy and diseased trees.     

Zusammensetzung der Neutralteile des Balsamkolophoniums von pinus sylvestris L., Pinus nigra austriaca Endl. und Pinus pinaster Ait

From the nonvolatile neutral diterpene components of the pine rosins carbonyls and alcohols (primary and secondary) were separated and the various fractions were analysed by GC and GC/MS. Resin aldehydes and alcohols having the same structure as the pine resin acids are the main components. The remaining neutral components are complex mixtures of diterpene hydrocarbons, tertiary alcohols, and resin acid methyl esters.     

Bestimmung der Cellulose, des Lignins und Kutins in der Rohfaser

Ohne Zusammenfassung(II. Mitteilung.)     

Die Bestimmung der Cellulose und des Lignins in den Futter- und Nahrungsmitteln

Ohne Zusammenfassung     

Tanninformaldehydharze aus den Rindenextrakten von Fichte (Picea abies) und Kiefer (Pinus sylvestris)

Polyphenols (tannins) were extracted from the bark of indigenous pine and spruce using organic solvents as well as aqueous solutions of alkali, sulphite and/or catalyst such as mineral acids and other inorganic chemicals, respectively. As far as yield and extract properties are concerned, the favorable conditions were: extraction with water in the presence of 1...10% sodium hydroxide (o.d. bark) and extract modifications with sodium sulphite (spruce) or phenol under acid conditions (pine), respectively, and extraction with mixtures of water (2 parts) and ethanol (3 parts) in the presence of 2...7% sodium hydroxide (o.d. bark). Yield was about 26% for pine bark and 35% for spruce bark. About 50...60% of the extracts were reactive polyphenolic compounds.     

Tanninformaldehydharze aus den Rindenextrakten von Fichte (Picea abies) und Kiefer (Pinus sylvestris)

Bark extracts from sproce and pine obtained with water or organic solvents were used as adhesives partly as binder additives, for manufacturing wood based boards. For plywood the extracts replaced about 60% (pine extracts) or 80% (spruce extracts) of PF-resin. The addition of more than 20% of extract reduced the wet bonding strength. Extracts were further used together with cold setting PRF-resin as adhesive for solid beech boards. They could replace the resin up till 30% without falling the boiling-water-resistance below the minimum values of DIN 68602. The mechanical properties of partieleboards bonded with unmodified extracts were low. The addition of PF-resin of düsocyanate as fortifier increased the strength values and reduced thickness swelling.     

Die Verteilung der Extraktstoffe im Stammholz von Pinus sylvestris L.

Yield and composition of extractives from sapwood and heartwood ofP. sylvestris differ greatly. While neutral lipids dominate in sapwood, free resin and fatty acids are the main constituents in heartwood. The extractive content in heartwood decreases with increasing trunk height. Beside the lipophilic components in the petrol ether extracts, carbonhydrates, low molecular lignin precursors and stilbene phenols (from heartwood only) can be obtained with more polar solvents.