Distribution of extractives in Sitka spruce (Picea sitchensis) grown in the northern UK

The distribution of acetone soluble extractives in Sitka spruce (Picea sitchensis) grown in Northern Britain was determined. Neither yield class, latitude, longitude nor thinning were found to have an impact on the total amount of acetone soluble extractives. More extractives were present in heartwood compared to sapwood but there were no significant differences in extractive content with stem height. A spectroscopic method capable of medium to high throughput of samples was developed to assess the relative amounts of aliphatic, carbonyl and aromatic functional groups in wood extractives. Heartwood contained a higher relative amount of aromatics than sapwood. Again no significant influence of site factors or stem height was found in terms of extractive composition. The low and stable extractive content of Sitka spruce contributes to its outstanding pulping properties and makes the wood ideally suited for applications like interior cladding or shavings for animal bedding where volatile extractives are of concern.     

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.     

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.     

Extractives, acidity, buffering capacity, ash and inorganic elements of black locust wood and bark of different clones and origin

Chemical properties of black locust wood and bark from Greece, Bulgaria and Hungary (clones NY, U and J) were investigated. Disks at breast height were taken from 25 black locust trees (five trees per origin and clone) and were divided into separate biomass components (juvenile heartwood, mature heartwood, sapwood and bark). Hot water soluble (HWSE) and dichloromethane soluble extractives (DSE), acidity (pH), buffering capacity, ash content and inorganic elements were determined according to standard laboratory techniques. Bark had the highest extractive content for both HWSE (9.25–13.49%) and DSE (3.09–4.03%). Differences of extractive contents in wood were found to exist between trees of different origin and between the three clones and ranged in heartwood between 5.04–10.10% for HWSE and 0.53–1.83% for DSE and in sapwood between 3.33–6.76% for HWSE and 0.48–1.47% for DSE. The higher values of pH occurred in sapwood (4.92–5.35), while the differences between bark (4.44–5.12) and heartwood (4.35–4.92) were small. Acid (ABC) and base (BBC) buffering capacities from the initial to pH 10 for ABC and to pH 3 for BBC were greater in bark (ABC 0.0172–0.0219 ml/ml and BBC 0.0079–0.0141 ml/ml) than in the other wood components (for heartwood ABC 0.0069–0.0159 ml/ml and BBC 0.0022–0.0096 ml/ml and for sapwood ABC 0.00330.0066 ml/ml and BBC 0.00330.0049 ml/ml). The total ash content was greater in bark (7.24–8.56%) than in other biomass components (for heartwood 0.34–0.89% and for sapwood 0.72–1.24%). The content of the main inorganic elements (Ca, K, Mg, Na, P) were also found to be much higher in bark while sapwood values were greater than heartwood.     

Zum Verhalten des Splint- und Kernholzes der Lärche (Larix decidua) bei der Herstellung von feuchtebeständigen Spanplatten unter Einsatz verschiedener Bindemittel

Chips from sap- and heartwood of 20, 40 and 102-year-old larch (Larix decidua) were prepared and chemically characterized. From the chips one-layer boards of 20 mm thickness were prepared using melamine-urea-phenol-formaldehyde resin (MUPF-resin), phenolformaldehyde resin (PF-resin), polymeric diisocyanate (PMDI), and tannin-formaldehyde resin (TF-resin). 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. Sap- and heartwood chips are different in their chemical properties as well as in bonding behaviour. The age of the tree has also an influence on the bonding characteristics of the chips. Thickness swelling, water absorption and equilibrium moisture content of heartwood boards were always lower than those of sapwood boards. Moreover, bending and internal bond strength of heartwood boards made from 20- and 40-year-old trees are much higher than those produced from sapwood. The strength properties of the boards deteriorate, however, with increasing age of the tree. This applies for both heartwood and sapwood boards. The water extractives of heartwood boards are of lower pH-value and higher buffering capacity than the corresponding boards from sapwood. Moreover, the emanation of acetic acid from heartwood boards is much higher than that of formic acid. In addition, boards from heartwood are in general of lower formaldehyde release compared with boards from sapwood. The addition of heartwood extractives to MUPF-resin increases the viscosity and gelation time of the resin and decreases its pH-value, whereas in case of PF-resin no such increase in the gelation time was registered. The extracts of heartwood increase the viscosity and gelation time of TF-resin.     

Variation of certain chemical properties within the stemwood of black locust (Robinia pseudoacacia L.)

From the bottom, middle, and top of three mature 35 to 37-year old black locust tree discs were cut and analysed to determine the variation within the stem of certain chemical properties. Hot-water extractive content was greater in heartwood than in sapwood, while the reverse occurred for the dichloromethane extractive content. Vertical stem analysis of hot-water extractives showed that they increased in heartwood but decreasedin sapwood from the bottom to the top of the stems while the reversal occurred for dichloromethane extractive content of sapwood. At the bottom and the middle of the stems, ash content was greater in sapwood than in heartwood, but at the top no difference was found between heartwood and sapwood. Ash content of both heartwood and sapwood was found to increase in the axial direction with respective values of 0.36% (bottom) and 0.76% (top) for heartwood and of 0.65% (bottom) and 0.76% (top) for sapwood. Ash analysis showed that considerable variations were found for the inorganic elements K and P being greater in sapwood than in heartwood. Heartwood was more acid than sapwood except for the top of the stems. Acidity mean values were found to increase from the bottom to the top of the stems in heartwood while they slightly decreased in sapwood. Total buffering capacity of heartwood was greater than that of sapwood and total buffering capacity of sapwood exhibited an inverse relationship to height. Very small acid equivalent values were determined only in sapwood. At the bottom, lignin content in heartwood (25.73%) was greater than in sapwood (18.13%). Lignin content of heartwood decreased from 25.73% at the bottom to 18.33% at the top, while that of sapwood was 18.13% at the bottom, 21.42% at the middle and 19.64% at the top.     

Die natürliche Dauerhaftigkeit von vier chilenischen Holzarten

The natural durability of the wood of Coigüe, Tepa, Ulmo and Olivillo against Coriolus versicolor, Coniophora puteana and Gloeophyllum trabeum was studied on the basis of numerous representative samples, and the results were statistically analyzed. All the wood species examined posses only a low natural durability towards the fungi tested: thus deviations from these results found in the literature presumably have to be traced back to the insufficient number of samples previously used. Mycelium growth of Coniophora puteana, determined on culture media with extractives from the sapwood and heartwood zones of the above species, showed no general correlation between the absolute amount of extractives and natural durability, except for Coigüe heartwood near to the sapwood.     

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.     

Density and moisture content forecasting based on X-ray computed tomography

X-ray computed tomography (CT) technology was applied for log nondestructive testing. The heartwood and sapwood of Larix gmelinii (Dahurian Larch) were scanned by CT system. The appropriate mathematical formulas between wood density and CT number were established for heartwood and sapwood respectively, because of the close relationship between wood density and CT number. The formulas between moisture content and CT number for heartwood and sapwood were built through experiment. The results indicate that though the differences of density and moisture content between heartwood and sapwood of L. gmelinii were not obvious, heartwood and sapwood had different formulas of forecasting wood density and moisture content by CT. The fitted relationships were very strong (coefficient of determination R² > 0.94).     

Thermal stability of <Emphasis Type="Italic">Abies alba</Emphasis> wood according to its radial position and forest management

Most of the defects affecting heat-treated wood quality are often attributed to heterogeneous heat transfers in industrial kilns. Even if interspecific variability of wood has been reported to affect thermal degradation of the material, little has been reported on the effects of intraspecific variability. The aim of this work was to study the effect of intraspecific variability of silver fir (Abies alba Mill.) wood on its thermal degradation. For this purpose, wood samples were sampled along the radius of cross-sections to estimate the effect of radial position on wood thermal degradation. Sampling was carried out on discs of four trees, two resulting from dynamic growth stand and two from standard growth stand. The study was performed at different scales: at wood compartments scale involving juvenile and mature heartwood, transition zone between heartwood and sapwood and sapwood as well as at intra-ring scale. Wood samples were ground to sawdust and subjected to thermogravimetric analysis and chemical analysis. Juvenile heartwood was shown to be more sensitive to thermal degradation than other compartments. The thermal behavior of sapwood was not particularly different from that of heartwood, and the presence of extractives did not influence significantly thermal degradation. Earlywood was more sensitive to thermal degradation than latewood explaining the higher susceptibility of fast growing heartwood containing larger rings with higher contents of earlywood.     

Radial variation of total phenol content in beech (Fagus sylvatica L.) wood with and without red heartwood

A comparative study of the radial distribution of the total phenol contents has been carried out on two Beech (Fagus sylvatica L.) discs, one with red heartwood and the other without red heartwood. The wood disc samples were investigated immediately after felling and at the different stages of room-drying. In the disc without red heartwood the concentrations increased from the bark towards the pith. In the disc with red heartwood the total phenol concentration rose steeply in front of the colour boundary, but this could only be measured in the fresh tissues. This suggests, that in these tissues either the formation of phenols (accumulation) is more intense or that special phenols are also formed. Beyond the boundary the concentration decreased dramatically. After drying of the wood samples the concentration decreased in all wood parts of the discs, but the amount of this is the highest in the white tissues next to the red heartwood. The results prove that the transformation of the phenols in the white tissues next to the colour boundary takes place faster.     

Comparison between heat treated sapwood and heartwood from Pinus pinaster

Sapwood and heartwood samples of Pinus pinaster were treated in an oven at 190 and 200 °C for 2–6 h. Dimensional stability, measured as Anti Shrinking Efficiency (ASE) between 0 and 65 % relative humidity, durability against fungi, mechanical resistance (MOE and MOR), hardness and chemical composition were determined for treated and untreated sapwood and heartwood. Radial ASE reached 52 % for sapwood and 50 % for heartwood, while tangential ASE reached 50 and 40 %, respectively. MOE increased slightly at the beginning of the treatment, decreasing afterwards. No significant differences were found between sapwood and heartwood. MOR decreased by 50 and 30 % for sapwood and heartwood, respectively. A significant increase in durability against Rhodonia placenta was found for both heartwood and sapwood at the higher temperature (200 °C), but at the lower temperature (190 °C) only heartwood showed good results.     

Spectral and chemical analyses of mould development on Scots pine heartwood

Scots pine heartwood specimens were exposed to mould in controlled humid atmosphere (RH 95%, T?=20 °C) and the responses of electrical impedance and Fourier transform infrared spectroscopy (EIS and FTIR) methods were studied. The concentration of methanol soluble heartwood extractives and the emission of volatile organic compounds (VOC) were determined from the parallel samples. Results show that the spectral responses and VOC emissions were related to the mould development. According to this study, VOC emissions might be used for discriminating mould susceptible and resistant samples. FTIR spectra showed that the relation of amide (1655 cm^-1) and carbonyl peaks (1736 cm^-1) was significantly affected by mould. In the EIS analyses, there also were electrical parameters, which were significantly affected by mould. In conclusion, both spectral methods hold potential for non-destructive mould detection and monitoring of mould development.     

Relationships between drying defect parameters and some growth characteristics in kiln-dried South African grown Eucalyptus grandis poles

Eucalyptus grandis wood is susceptible to serious drying defects and all possible measures before and during kiln drying of poles need to be taken to minimize the defects. In order to identify factors that may affect drying quality of poles, the objective of this study was to assess relationships between surface check total length and depth, MC gradient, honeycomb percentage of pole cross section area, extent of collapse, sapwood depth, heartwood percentage of pole cross-sectional area, green MC and pole diameter. The defects were measured on 3 loads of 10?kiln-dried E. grandis poles, using a different drying schedule for each load. After measuring surface check length using a measuring tape and check depth using feeler gauges and a ruler, poles were cross cut at the theoretical ground line (TGL) 1.5?m from the butt end, to measure the MC gradient between the shell and core of poles. Digital image analysis of cross sections of discs cut at TGL was used to measure sapwood depth, and the areas of honeycomb, heartwood and disc cross section. Collapse was assessed using qualitative methods. Results showed that surface check total length was positively correlated with sapwood depth, and the average depth of surface checks was greater than the average sapwood depth. MC gradient between the shell and core was positively correlated with green MC while the transformed honeycomb percentage and collapse class were both positively correlated with heartwood percentage. It was concluded that pole drying defects are related to sapwood depth, green MC and heartwood percentage, and if pre-sorting of poles by these characteristics is done and appropriate kiln schedules are used, drying defects can be minimised.     

Vergleich der Extrakte und des Lignins aus frischem und gelagertem Kiefernholz (Pinus sylvestris L.)

The degradation processes of the extractives of pine wood caused by aging are only noticeable in the heartwood. In seasoned sapwood the percentages of the water extracts and the cyclohexane-ethanol extract increase compared with the green sample; the alkali extracts, however, do not vary. The contents of acid lignin as well as the UV and IR spectra of MWL do not show differences. The amount of OCH₃/C₉ is in all samples 0.96, but the degree of oxidation is higher in the seasoned wood than in the green one.     

Über die Tränkbarkeit von vier chilenischen Holzarten in Abhängigkeit von Standort und Holzeigenschaften

Several series of small samples of the economically important Chilean wood species Coigüe (Nothofagus dombeyi), Tepa (Laurelia philippiana), Ulmo (Eucryphia cordifolia) and Olivillo (Aextoxicon punctatum), from three different sites were treated with cold aqueous solutions and hot creosote. Excepting Coigüe-heartwood, all species could easily be treated longitudinally; the retentions were 500 to 700 kg/m³. The radial and tangential retentions in the sapwood as well as in the inner part of Tepa, which forms no heartwood, were between 7 and 18 kg/m³, the heartwood retention in Ulmo and Olivillo was between 3,5 and 7kg/m³. The tretability of Tepa depended significantly on the site of tree growth and the treatability of Coigüe and Ulmo on the individual trees. The retention values for heartwood were improved by dissolving extractives during treatment with hot creosote.     

Antioxidant and antifungal activities of extracts from 15 selected hardwood species of Malaysian timber

The antioxidant activities, total phenols and antifungal activities of 35 extracts samples from 15 species of Malaysian timber were investigated. The methanol extracts from Mangifera indica heartwood were found to have superior antioxidant activity with an EC₅₀ value of 4.71±0.89 μg/ml. Antioxidant activities correlated with total phenols contents. The methanol extracts from Neobalanocarpus heimii bark and Cinnamomum porrectum heartwood showed moderate antifungal activity against a brown-rot fungus, Gloeophyllum trabeum. The methanol extracts from Neobalanocarpus heimii bark and Endospermum malaccense inner wood showed the highest antifungal activity against a white-rot fungus, Pycnoporus sanguineus, at a minimum effective amount of 100 μg. The activities of these extracts were equal to the activity of the positive control, glycyrrhizic acid dipotassium salt, suggesting that they have great potential as a source of fungistats.     

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.     

Primer cure and adhesion after light organic solvent preservative treatment of Radiata pine

This study examined the effect of preservative treatment and wood drying history on paint primer cure and adhesion for New Zealand radiata pine (Pinus radiata D. Don). Double Vacuum LOSP treatments resulted in a significantly lower LOSP uptake than did Lowry treatments, for both sapwood and heartwood. Wood drying history had no effect on uptake by sapwood, but did affect uptake by heartwood; high-temperature-kiln-dried heartwood retained more solvent than air-dried or conventionally dried heartwood. For sapwood, LOSP treatment method and wood drying history did not significantly affect either primer cure or primer adhesion. For heartwood, primer adhesion in the early stage of cure was better with Double Vacuum treatments. Double Vacuum treatments also resulted in a higher cure of primer, two days after priming, than did Lowry treatment when either conventionally or high-temperature-kiln-dried heartwood was used, but no significant difference was found with air-dried heartwood. It was concluded that, for radiata pine heartwood, Double Vacuum treatment, combined with either air-drying or conventional drying, will reduce LOSP uptake and give better primer performance, so long as effective ventilated solvent removal is achieved before priming.     

The water absorption of sapwood and heartwood of Scots pine and Norway spruce heat-treated at 170 °C, 190 °C, 210 °C and 230 °C

Heat-treatment changes the chemical and physical properties of wood. Wood polymers are degraded, dimensional stability is enhanced, equilibrium moisture content is lowered, colour darkens and biological durability is increased. The properties of heat-treated wood have been researched considerably, but the differences between sapwood and heartwood have not been reported separately. In this research, water absorption differences between sapwood and heartwood of Scots pine and Norway spruce heat-treated at temperatures 170 °C, 190 °C, 210 °C and 230 °C were investigated. The results were compared to industrially kiln-dried reference samples. Water absorption was determined with a floating test based on the EN 927-5 standard. The heartwood of both wood species absorbed less water than sapwood. Heat-treatment evidently decreased the water absorption of spruce and pine heartwood. The higher the heat-treating temperature, the lower the amount of absorbed moisture. However, a very interesting exception was pine sapwood, whose water absorption actually increased with heat-treatment after the three lowest heat-treatment temperatures compared to the reference material. Water absorption did not decrease until the heat-treatment temperature was 230 °C.