Volume 66, Issue 2

With the aim of investigating kraft lignin as a raw material for carbon fibre production, different lignins have been stabilised in air at conditions varied according to a full factorial experimental design. The lignins under examination were purified kraft lignin powders originating from birch, spruce/pine and Eucalyptus globules , as well as lignin fibres originating from birch with 5% poly(ethylene oxide) (PEO) added as a plasticiser. The influence of temperature, time and heating rate on yield and glass-transition temperature (T g ) was investigated. The highest yield was achieved after stabilisation at 280°C during 2 h with a heating rate of 0.2°C min -1 . The T g of all lignin powders was increased when stabilisation occurred under harsher conditions. X-ray photoelectron spectroscopy analysis (XPS) of both the outer surface and the cleaved cross-section of individual lignin/PEO fibres showed a clear gradient in the degree of chemical modification, with the major change occurring on the surface resulting in the appearance of a skin-core structure after stabilisation. The behaviour of the lignin fibres during stabilisation is similar to that of pitch-based fibres, indicating good possibilities for lignin as raw material for carbon fibre production.

Galactoglucomannans (GGMs) are water-soluble polysaccharides released and accumulated in process waters in the production of thermomechanical pulp. The general trend in the forestry industry is moving towards bio-refineries, for example utilizing these hemicelluloses as bioactive substances. At present, there is no industrial use of wood-derived mannans. In this study, GGMs extracted from thermomechanical pulp, as well as further carboxymethyl-ated galactoglucomannans (CM-GGMs), were sulfated to increase their antithrombotic properties. The products were characterized with Fourier transform infrared spectroscopy, nuclear magnetic resonance and capillary electrophoresis. The carbohydrate composition and sulfur amounts were determined. The products’ total charges were determined by polyelectrolyte titrations and their antithrombotic effect was measured based on the activated partial thromboplastin time. The results showed a significant increase in the antithrombotic effect of the sulfated galactoglucomannans from spruce wood and thus a potential new use for wood-derived mannans.

The recycling potential of unbleached and bleached pulps of juvenile and mature wood of poplar (namely “eastern cottonwood”, Populus deltoides ) has been investigated. First, chemical and morphological characteristics of juvenile wood (JW), transition wood, and mature wood (MW) of the trunk were determined. Then, high yield and low yield pulps were produced separately from JW and MW by kraft pulping (KP), followed by bleaching of the low-yield pulp with a DED sequence. The obtained handsheet papers were subjected to five successive drying and rewetting cycles (as recycling simulation), and the properties of the corresponding pulps were characterized. The results show that JW is inferior with respect to chemical and morphological properties and resulted in low-yield KP. The bleached pulp obtained from JW required more bleaching chemical to achieve the brightness targets. The strength losses of pulps resulting from recycling were more significant in the first recycling cycle, and then the loss rate decreased with further cycles. The comparison between different pulps showed that the JW pulps were more susceptible to the effects of recycling than MW pulps.

Spruce samples, naturally aged for 200, 400 and 500 years, artificially aged by a hydrothermal treatment (at 180, 160 or 130°C, relative air humidities of 14%, 40%, or 60% and for treatment times between 1 to 50 h), as well as reference samples, were analysed by Fourier transform infrared spectroscopy (FTIR) attenuated total reflection (FTIR-ATR) and ultraviolet resonance Raman (UVRR) spectroscopy. Natural ageing mostly affected the hemicelluloses and lignin, as observed from the FTIR-ATR and UVRR spectra, respectively. The UVRR spectra of the same samples after acetone extraction indicated that lignin was partially degraded and quinone structures were possibly formed. Artificial ageing at 160°C showed a significant change in the lignin structure, a well-known effect in the thermal treatment of wood, whereas treatment at 130°C did not alter the wood structure to any significant extent. Principal component analysis of the UVRR spectra confirmed that the spectra of artificially aged wood up to 160°C are dissimilar to naturally aged wood and which are also dissimilar to unaged wood.

A method has been developed for the characterization of biologically active silver birch ( Betula pendula ) inner bark phenolics based on high-performance liquid chromatography/diode array detector (HPLC-DAD)/electrospray ionization-mass spectrometry (ESI-MS). It was demonstrated that the inner bark contains high amounts of flavonoids, arylbutanoids, diarylheptanoids, simple phenolic compounds, phenolic acids, lignans, and procyanidins. Altogether, 30 individual compounds were characterized based on their ultraviolet (UV) and MS data. Structures of 22 compounds were confirmed by nuclear magnetic resonance (NMR) spectroscopy. In addition to previously reported phenolic compounds, 12 compounds were identified in silver birch inner bark for the first time; two of them are novel compounds: 3- β -glucopyranosyloxy-2-hydroxy-1-(4-hydroxy-3-methoxy-phenyl)-propan-1-one and 1,7-bis-(4-hydroxyphenyl)-3-heptanol 3- O - β -ap-iofuranosyl-(1→2)- β -glucopyranoside.

In the present study, one sesquiterpene synthase gene in Eleutherococcus trifoliatus was identified and characterized. Full-length cDNA was obtained from stems. It contained an open reading frame of 1671 bp ( EtCop ) with a predicted molecular mass of 64.5 kDa. The amino acid sequence of EtCop contained the common terpene synthase family motifs RR(x) 8 W, RxR and DDxxD. The recombinant protein from Escherichia coli was incubated with farnesyl diphosphate in order to identify the function of EtCop . The product of EtCop could be identified as an α-copaene by means of gas chromatography-mass spectrometry analysis and comparison with an authentic standard.

Fungal degradation alters the microstructure of wood and its physical and chemical properties are also changed. While these changes are well investigated as a function of mass loss, mass density loss and changes in equilibrium moisture content are not well elucidated. The physical and chemical alterations are crucial when linking microstructural characteristics with macroscopic mechanical properties. In the present article, a consistent set of physical, chemical and mechanical characteristics is presented, which were measured on the same sample before and after fungal degradation. In the first part of this two-part contribution, elucidating microstructure/stiffness-relationships of degraded wood, changes in physical and chemical data are presented, which were collected from specimens of Scots pine ( Pinus sylvestris ) sapwood degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks degradation time. A comparison of mass loss with corresponding mass density loss demonstrated that mass loss entails two effects: firstly, a decrease in sample size (more pronounced for G. trabeum ), and secondly, a decrease of mass density within the sample (more pronounced for T. versicolor ). These two concurrent effects are interrelated with sample size and shape. Hemicelluloses and cellulose are degraded by G. trabeum , while T. versicolor was additionally able to degrade lignin. In particular because of the breakdown of hemicelluloses and paracrystalline parts of cellulose, the equilibrium moisture content of degraded samples is lower than that in the initial state.

Fungal decay considerably affects the macroscopic mechanical properties of wood as a result of modifications and degradations in its microscopic structure. While effects on mechanical properties related to the stem direction are fairly well understood, effects on radial and tangential directions (transverse properties) are less well investigated. In the present study, changes of longitudinal elastic moduli and stiffness data in all anatomical directions of Scots pine ( Pinus sylvestris ) sapwood which was degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks have been investigated. Transverse properties were found to be much more deteriorated than the longitudinal ones. This is because of the degradation of the polymer matrix between the cellulose microfibrils, which has a strong effect on transverse stiffness. Longitudinal stiffness, on the other hand, is mainly governed by cellulose microfibrils, which are more stable agains fungal decay. G. trabeum (more active in earlywood) strongly weakens radial stiffness, whereas T. versicolor (more active in latewood) strongly reduces tangential stiffness. The data in terms of radial and tangential stiffnesses, as well as the corresponding anisotropy ratios, seem to be suitable as durability indicators of wood and even allow conclusions to be made on the degradation mechanisms of fungi.

The off-axis Young’s modulus and off-axis shear modulus of wood were obtained by conducting a flexural vibration test under the free-free condition, and performing a subsequent numerical analysis on the test data. The relationship between the off-axis Young’s modulus and the off-axis angle was obtained. In contrast, the relationship between the off-axis shear modulus and the off-axis angle was discrepant from that predicted by the transformation rule based on the conventional hypothesis that Timoshenko’s shear factor is 1.2. When the dependence of the shear factor on the off-axis angle was taken into account, however, the off-axis shear modulus could be obtained properly.

Tracheid dimensions influence the quality of wood and that of pulp and paper. Both between- and within-ring variations are influenced by tree developmental stage, site, genetics, and forest management. To contribute to the knowledge in this regard, the radial and tangential tracheid dimensions on Norway spruce, defined as the lumens and double cell wall thickness, have been measured using a SilviScan device. Namely, 4947 annual rings from 35 trees from plantations in France, Norway, and Sweden were examined. Mixed-effects models were constructed concerning the radial and tangential tracheid widths for the total ring and in three within-ring compartments – earlywood (EW), transition wood (TW), and latewood (LW) – as functions of age, radius, height in the tree, and growth rate. Between-site and between-tree variations were also considered. The mean radial tracheid width was 34.2 μm (EW), 29.9 μm (TrW), and 22.1 μm (LW). The tangential tracheid width was on average 30.1 μm in all compartments. The radial and tangential tracheid widths in the rings and compartments increased from the pith to the bark and decreased with greater growth rates. Within a given ring, both properties decreased with height in the tree. The fixed part of the models of the radial tracheid width accounted for 68% (EW), 45% (TW), and 33% (LW) while for the models of the tangential fibre width it accounted for 42% of the variation in all compartments. Climate or hydraulic maintenance was hypothesised to be responsible for the variation of the radial tracheid width.

Tonewood for musical instruments is quarter-sawn and frequently quality-graded based on visual appearance, mechanical and acoustic properties. The assessment uses simple human (subjective) observation, and two “experts” can rate the same sample differently. This paper describes the application of integral transforms (Fourier and Radon) for automatic (objective) assessment of the visual appearance of 10 Sitka spruce ( Picea sitchensis ) sample images. This work considers surface classification on the basis of grain orientation, count, spacing, and evenness or uniformity.

Scots pine sapwood ( Pinus sylvestris L.) and European beech wood ( Fagus sylvatica L.) were treated with glutaraldehyde (GA) in aqueous solution in the presence of magnesium chloride as a catalyst to evaluate the durability improvement towards staining and rot fungi. The GA modified specimens were dipped in a spore suspension of the blue stain fungus Aureobasidium pullulans and incubated for 8 weeks. The growth on both pine and beech wood was restrained, when the weight percent gain (WPG) of the specimens was above 7%. Under this condition, GA-modified beech wood did not suffer any mass loss after incubation with the white rot fungus Trametes versicolor. The threshold to prevent decay of beech and pine specimens towards the brown rot fungus Coniophora puteana was at a WPG of only 3%. GA treatment to a WPG over 6% protected the Scots pine stakes from soft rot decay during 32 weeks’ exposure according to ENv 807 (2001).

Development of new wood preservative systems is a lengthy and expensive endeavor. This study examined soil block experiments with a longer incubation time than typical to make the test harsher, using commercial particulate copper azole (PCA), soluble copper azole (CA-C), and soluble alkaline copper quaternary (ACQ-D) systems. Both the CA-C and PCA systems performed poorly compared to ACQ-D with two copper tolerant fungi, even at retentions well above the specified ground-contact residential level, i.e., Use Category 4A (UC4A). With the one copper sensitive fungus examined, PCA and ACQ-D prevented decay at about half the UC4A retention. To compare these laboratory efficacy results, data from an outdoor accelerated post test with a copper tolerant fungus gave efficacies of ACQ > CA-C >> PCA, with PCA having significantly more decay than the two soluble copper systems. Further confirmation was obtained from recently published E7 stake data conducted at a site with extensive copper tolerant fungi, which suggested that ACQ performed better than PCA and CA-B after about 3 years of exposure in agreement with the harsh soil block results with the two copper-tolerant fungi. Conversely, results from four other sites without a history of extensive copper tolerant fungi are interpreted that all three systems generally performed adequately, which is compatible with the soil block test with the one copper sensitive fungus examined.

Scots pine ( Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in un-even distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

The effect of consolidation is proportional to the content of polymer in wood, i.e., to the ability of wood to absorb a polymer solution. One of the ways of increasing the absorption of the polymer solution is its modification by a surfactant. This article evaluates in detail the impact of non-ionic, anionic, and cationic surfactants on penetration of the ethylmethacrylate and methacrylate copolymer solution (Paraloid B72 in toluene) into lime wood by capillary rise. The impact of surfactants is evaluated on the basis of the solution surface tension, the contact angle of a sessile drop, and absorption of the solution by wood. Anionic and non-ionic surfactants based on polyoxyethylene had a positive impact on penetration of Paraloid B72 solution due to their ability to form inverse micelles in toluene. Fluorinated surfactants, polydimethylsiloxane-based surfactants, and cationic surfactants worsen its penetration.

Experiments were performed to find potential sources for enzyme production for the pulp and paper industry and for biological ethanol production by screening the cellulase, xylanase and β-xylosidase activities of 36 species of Penicillium isolated from various wood materials in Korea. Rice straw powder (RiceP), birchwood xylan (BirchX), and beechwood xylan (BeechX) were supplied as individual carbon sources for the Penicillium species. All Penicillium species tested in this study showed little cellulase activity, but some species exhibited remarkably high xylanase and β-xylosidase activities, as determined by a filter paper assay. P. oxalicum showed the greatest xylanase activity on RiceP (158.70 U ml -1 ). On the other hand, P. brevicompactum produced the highest active β-xylosidase on BirchX (6.25 U ml -1 ).

The densification of wood leads to better mechanical properties, e.g., an increased hardness and dimensional stability. However, densified or shaped wood in contact with water springs back into its original shape without fixation. Hence, the aim of this study was the development of a combined densification and fixation procedure. Beech wood samples ( Fagus sylvatica L.) were impregnated with a solution consisting of furfuryl alcohol and maleic anhydride. The compression of these impregnated samples to approximately 30% followed by a curing process in a heating press resulted in a significant increase of hardness and dimensional stability. The spring-back-effect was clearly reduced by the in situ polymerization of the furfuryl alcohol solution to furan resins.

No abstract available