Volume 69, Issue 5

The residual lignin (L R sample) was isolated from unbleached acid sulphite pulp from Eucalyptus globulus with kappa number 18.2 by acidolysis and structurally characterized by wet chemistry and NMR techniques. The main structural features of L R were compared with lignin isolated from sulphite spent liquor (L SSL sample) and dioxane lignin (DL sample) from eucalypt wood. L R contains less sulphonic groups (4.4%) compared to L SSL (11.3%), and its molecular weight (2200 Da) is very close to that of DL (2600 Da). A part of sulphonic groups is located at the benzylic carbon in β - O -4′ and β -5′ structures. L R revealed ca. 20% lower abundance of β - O -4′ structures than DL, but ca. 40% higher abundance of these structures than L SSL . The degree of condensation of L R was higher than that of DL but lower than that of L SSL . The condensed structures in L R mainly originate from C6-linked syringyl units. The structural peculiarities of L R consisted of the relatively high proportion of syringyl units compared to DL and the strong structural association with hemicelluloses via benzyl ether linkages. The differences in the structure of residual lignins from eucalypt sulphite and kraft pulps have been discussed.

Lignin can be converted into monomeric products with the aid of molten salt media. Molten zinc chloride (ZnCl 2 )/potassium chloride (KCl) mixtures are suitable for this purpose. The application of an eutectic mixture with low melting points leads to similar main products as are obtained by pyrolysis. The hydrogenolysis of an organosolv lignin in molten salts of ZnCl 2 /KCl was investigated as a function of reaction temperature, residence time, and lignin concentration, and the composition of liquid products and monophenols was analyzed by gas chromatography-mass spectrometry (GC-MS). The yields can be optimized by the proper selection of the reaction temperature. A longer residence time and higher lignin concentrations lead to increased formation of solid residues and gaseous products. The liquid products mainly consist of substituted phenols derived from lignins. Polymeric products are the result of condensation reactions (i.e., the formation of new C-C linkages in the course of secondary reactions).

An efficient, nontoxic, and solvent-free oxyalkylation of European beech wood organosolv lignin (OL) has been developed. Two approaches were studied: a direct reaction of lignin with propylene carbonate (PC) and a two-step reaction of lignin with maleic anhydride (MA) followed by oxyalkylation with PC. The structural analysis of lignin polyols was performed by 1 H NMR, 13 C NMR, 31 P NMR, and FTIR spectroscopy. It was demonstrated that PC was able to almost completely oxypropylate aliphatic and phenolic OH groups. Moreover, the carboxylic acid groups of maleated OL were fully oxypropylated by PC. This modification strongly facilitates the generation of a uniform lignin polyol applicable as a biobased component in polyurethanes and polyesters based on cyclic organic carbonates.

Lignosulfonic acid (LS) has been applied both as dispersant and dopant for chemical polymerization of 3,4-ethylenedioxythiophene (EDOT). EDOT is successfully polymerized in LS aqueous solutions, resulting in a water-dispersive poly(3,4-ethylenedioxythiophene) (PEDOT) conductive nanoparticle (PEDOT:LS). The structure, intermolecular interaction, and performance of the PEDOT:LS were investigated by ultraviolet-visible-Near-infrared spectrophotometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, dynamic light scattering, transmission electron microscopy, X-ray photoelectron spectroscopy, and surface resistivity tester. Results were interpreted in a way that PEDOT:LS is a polyelectrolyte complex, in which the highly hydrophobic PEDOT is in the inner part of the particle and the LS-rich layer with high hydrophilicity is on its surface. During oxidizing reaction of EDOT to PEDOT in LS, the water-insoluble PEDOT product is adsorbed on the surface of water-soluble LS by electrostatic attraction and forms PEDOT:LS polyelectrolyte complexes. In this process, excess LS is needed to be adsorbed on the surface of PEDOT:LS complexes. The process is driven by π-π interaction to increase the water solubility and contributes to a continuous polymerization. The PEDOT:LS as coating has a good conductivity, transparency, humidity resistance, water resistance, and thermal stability and can be used as high-performance antistatic agents.

The wood of Cryptomeria japonica D. Don was liquefied in ethylene glycol (EG) with sulfuric acid (H 2 SO 4 ) as a catalyst at 150°C for 60 min. The liquefied wood (LW)- and EG-based polyester polyols (EG-Poly est.-ol ) were synthesized by reacting LW and EG with adipic acid (AA), respectively. Polyurethane (PUR) resins were made by mixing Poly est.-ol with isocyanate. The results show that LW-Poly est.-ol is a suitable raw material for PUR. The PUR films prepared with LW-Poly est.-ol have higher tensile strength with less elongation at breaking point than that with EG-Poly est.-ol . According to dynamic thermomechanical analysis, the PUR films prepared with EG-Poly est.-ol have a homogeneous molecular structure, whereas a phase separation has been found for those made with LW-Poly est.-ol . Thermal gravimetric analysis showed that the thermal degradation of LW-PUR films only starts at higher temperature than that of EG-PUR.

Scots pine ( Pinus sylvestris L.) was subjected to relative humidity (RH) changes, and the dynamic strain field on the surface and in the bulk wood was monitored by digital speckle pattern interferometry and X-ray computed microtomography assisted by digital volume correlation. If a freely shrinking specimen was subjected to an RH decrement, earlywood (EW) and latewood (LW) at the surface layer were deformed in the opposite directions at the beginning of drying due to moisture gradient across the specimen. As a result, the surface and core behaved as independent sub-components, with the surface restrained in its response by the dimensionally unchanged core. With time, both LW and EW shrank as moisture content (MC) became uniform across the specimen. When an entire wood specimen was restrained from movement and desiccated in ambient RH, EW was stretched to compensate for the considerable shrinkage of LW. Knowledge about surface deformation at the annual ring level as a function of varying RH may be helpful to assess the risks associated with the damage of paint layers caused by fluctuations of ambient RH.

A newly developed thermo-hydro treatment (THT) for use in a one-stage heat treatment process was examined by focusing on the form stability-related properties of European aspen ( Populus tremula ), birch silver ( Betula pendula ), and gray alder ( Alnus incana ). In particular, wood specimens were subjected to THT in a saturated steam atmosphere in a pilot-scale autoclave heated between 140 and 180°C for 1–3 h. Several parameters of untreated and treated samples after several soaking and drying cycles were compared, namely, the changes in the volumetric swelling, swelling in the radial and tangential directions, cell wall total water capacity, and anti-swelling efficiency (ASE). Due to repeated wetting in the cyclic water submersion-drying test, the original ASE of 73% decreased to 65% (180°C for 1 h), and the original ASE of 33% decreased to 5% (140°C for 1 h). Wood modified at 170°C presented good results that were not significantly lower than wood treated at higher temperatures while consuming less energy to deliver ASE improvement and was selected as optimum. To increase the ASE by 1%, the amount of energy consumed was decreased by 41%, 39%, and 17% compared with the treatment regimes of 160°C for 1 h, 160°C for 3 h, and 180°C for 1 h, respectively. The new THT regime led to improved long-term dimensional stability due to the cross-linking of cell wall polymers, which resulted in increased cell wall rigidity.

The focus of this study is the variation of practical shrinkage strain, elastic strain, viscoelastic creep strain, and mechanosorptive creep characteristics of white birch ( Betula platyphylla Suk) disks caused by shrinkage anisotropy (ShrA) and its interaction with moisture content (MC) gradient. The rheological properties of white birch disks have been analyzed as a function of MC based on two different drying schedules at constant and increasing temperature. The drying conditions influence the strains remarkably. The stress characteristics and stress reversal mechanism under the conditions of increasing temperature are discussed based on stress analysis diagrams. Under both drying schedules, the wood disks are initially subjected to tangential tensile stress, and with decreasing MC, the tensile stress turns into compressive stress. Before stress reversal, the stresses of ShrA and MC gradient are aligned in the same direction and then point in opposite directions.

Picea glehnii is one of the most important plantation species in Hokkaido, Japan. Basic density (BD) and microfibril angle (MFA) of the S2 layer in latewood tracheid in 16 full-sib families and their six parental clones planted in Hokkaido were examined to clarify among-family and clonal variations of wood properties and their inheritance from parents to offspring. Mean values of BD and MFA in full-sib families and parental clones were 0.36 and 0.35 g cm -3 and 16.1° and 10.7°, respectively. Estimated repeatabilities of BD and MFA in juvenile wood (jW) were higher than those in mature wood. In addition, larger genetic coefficient of variation was detected for jW, indicating that improvement of jW properties is important to Hokkaido’s tree breeding program. Parent-offspring correlation coefficients were positive and significant in all properties. These results suggest that the influence of parental clones on wood properties is inheritable to offspring. Moreover, there were no significant differences between reciprocal crosses of wood properties, suggesting that plus-tree clones with good wood properties can be used as either female or male parents for producing offspring. There is a possibility of improving wood properties in P. glehnii by crossing clones with desirable properties.

The effects of exposing specimens of Oriental beech [ Fagus sylvatica subsp. orientalis (Lipsky) Greuter and Burdet] to the white-rot fungi Pleurotus ostreatus (Jacq.: Fr.) Kummer and Trametes versicolor (L.: Fr.) Pilát strain 325 have been studied concerning the mechanical properties and chemical composition in terms of carbohydrates, cellulose, and lignin. Biological decay tests were carried out in accordance with the EN 113 standard specifications for 30 and 120 days. P. ostreatus had nearly the same deteriorating effects on the mechanical properties and chemical composition as that caused by T. versicolor . High and significant correlations were found between some mechanical properties with chemical components; for instance, the correlation coefficient (R 2 ) between impact bending and carbohydrate content was about 0.96. The changes of components influence the various mechanical properties to a different degree. Incipient fungal decay caused severe changes for impact bending and carbohydrate loss. Several other properties declined at 120-day exposure time, such as the hardness, compression strength parallel to grain, and cellulose and lignin losses.

The development of appropriate chemical precursors that can covalently functionalize natural wood aims at efficient restriction of deterioration. Biological staining experiments were performed with veneer pieces made of sapwood of Scots pine ( Pinus sylvestris L.) that had previously been chemically modified with substituted benzoates. Based on the recently published protocol on esterification of wood by means of 1 H -benzotriazole activation, the quantity of covalently bonded organomaterials (QCOs), a recently defined advantageous value considering the individual molecular weight of the functionalizing organochemical groups, was obtained in the range of 0.9–1.5 mmol g -1 . The modified wood was analyzed by attenuated total reflection IR spectroscopy. Modification with three electronically different benzoates clearly reduced the colonization of the specimen’s surfaces by the blue stain fungus Aureobasidium pullulans but did not fully prevent it. The degree of colonization appeared to decrease with increasing QCO values of the modification agents but apparently did not strongly depend on the additional functionality of the benzoate.

Changes in structure and lignin chemistry were investigated in ash wood thermally modified (TMW) by the thermo-vacuum (Termovuoto) process for 3 h at 190–220°C by means of light, fluorescence, and transmission electron (TEM) microscopy combined with histo/cytochemistry. Variation in changes in native cell color in TMWs was positively correlated with differences in lignin content between cell types and cell wall regions in the reference wood. Histochemical staining showed increasing amounts of acidic groups in TMWs with different response to ethanol extraction between secondary cell walls and CML cc (compound middle lamella/middle lamella cell corner) regions. Fluorescence microscopy of TMWs and references showed a difference in intensity and color emission of lignin autofluorescence, reflecting modification of lignin in TMWs. Changes in histochemistry and fluorescence were prominent at and above 200°C. With TEM, increased intensity of lignin staining and distortion of fiber S 1 layers were detected in TMW treated for 3 h at 220°C (TMW 3 h, 220°C ). TMW 3 h, 220°C differed significantly in molecular ultrastructure of fiber cell walls compared to references, such as loss of the lamellar structure and size and distribution of lignin aggregates. The modification in CML cc structure in ash TMW 3 h, 220°C is different from that of softwoods.

Following structural and cytochemical studies (Part I) on thermally modified ash wood (TMW) by the thermo-vacuum (Termovuoto) process, changes in the distribution of noncellulosic polysaccharides have been investigated in TMW treated for 3 h at 220°C (TMW 3 h, 220°C ) by means of immunogold localization methods. Pectins (homogalacturonan, rhamnogalacturonan-I) and xyloglucan were significantly degraded in compound middle lamella (CML), including the middle lamella cell corner regions (CML cc ), of all xylem cells after thermal modification. Xylan and mannan degradation were also visible in fiber cell walls. In particular, degradation of mannan was very significant and showed variation between cell wall regions even within the same cell wall. The degradation of pectins was more significant than that of hemicelluloses. In summary, results suggest that each noncellulosic polysaccharide may have a different degradation process in ash TMWs.

This study investigates the effects of fiber dimensions on hardboard properties. Fiber size is determined by the amount of energy applied during refining, and fiber size affects board properties; that is, production cost and board performance are closely related. Therefore, in the present paper, the effects of fiber dimensions on hardboard performance have been investigated. To optimize the hardboard process, fiber size was varied via screening, and the screen fractions were further classified using a Bauer-McNett apparatus. Hardboards were produced with mixtures of classified fibers. Bending strength, internal bond, and thickness swelling of the final boards were evaluated according to EN 310, EN 319, and EN 317, respectively. The effects of fiber size on the investigated properties were analyzed by means of multivariate linear regression. Generally, a higher proportion of small fibers appears to improve board performance presumably due to the higher specific surface area of fibers, which facilitate interfiber bonding.

The dynamic water vapor sorption of untreated, acetylated (W ac ), and formaldehyde-treated (W FA ) Scots pine ( Pinus sylvestris L.) sapwood was studied in a dynamic vapor sorption apparatus to assess the effects of cell wall bulking and cross-linking. Both modifications resulted in a considerable reduction of reduced equilibrium moisture content (EMC R ), the corresponding equilibrium times, and hysteresis in the hydroscopic range of wood. Acetylation reduced the adsorption and desorption of water at each given relative humidity (RH) step from 0% to 95% RH, whereas formalization affected the sorption behavior of wood solely above 20% RH. From 20% to 95% RH, the EMC ratio of W FA to its control steadily decreased, whereas the EMC ratio of W ac was still constant in this RH range. Below 20% RH, the sorption behavior of W ac was governed by hydroxyl blocking, whereas that of W FA was hardly influenced compared with the control. Above 20% RH, the sorption behavior of W ac was solely determined by cell wall bulking, whereas that of W FA was governed by the increased matrix stiffness due to the cross-linking of cell wall polymers.

The antioxidant, anti-inflammatory, antivirus, uric acid decreasing, and hepatoprotective activities of Acacia confusa extracts were demonstrated in previous studies. However, there is no scientific evidence concerning the immune-regulatory activity of the heartwood extract of A. confusa . In this study, the effect of a methanolic heartwood extract (MHE) from A. confusa on dendritic cell (DC) activation and function was examined. A. confusa MHE significantly reduced the production of pro-inflammatory cytokine interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated DCs, and the effective concentration (25 μg ml -1 ) of A. confusa MHE did not affect cell viability. Additionally, the bioactive phytochemical from A. confusa MHE, melanoxetin, was isolated and purified by HPLC. This substance inhibited the production of pro-inflammatory cytokines (tumor necrosis factor-α, IL-6, and IL-12) in LPS-stimulated DC at a concentration of 12.5 μM. Moreover, the expression levels of co-stimulatory molecules such as CD40, CD80, and CD86 also remarkably decreased after treatment with melanoxetin at the same dose. These findings indicate that A. confusa MHE and melanoxetin have excellent immune-suppressive activity and may be potential candidates for further development of natural health supplements.

The mechanical performance of wood-based composites is determined by the mechanical properties of their individual components and the effective load transfer between these components. In laminated wood composites, this load transfer is facilitated by the adhesive bond. The experimental methodology developed in this study measures and analyzes the full-field deformation and strain distributions across the loaded wood-adhesive interphase at a micromechanical level. Optical measurements were performed based on the principles of digital image correlation by a stereomicroscopic camera system. This system allows the monitoring of in-plane deformations as well as out-of-plane displacements, providing full-field 3D surface strain maps across the adhesive bond. These measurements can be used to improve the understanding of the load transfer between the adherents and the contribution of the adhesive to the mechanical properties of the bulk composite and serve as a quantitative input for numerical modeling and simulations aimed at the improvement of the products.