Volume 70, Issue 6

The selective lignin degradation in a LCC was proceeded with the γ-TTSA method, which is a selective cleavage method for β-O-4 linkages in lignins, in order to obtain more precise information concerning LCC bonding sites. To this purpose, crude MWL from Eucalyptus globulus , containing lignin and xylan, was treated by the γ-TTSA method. This approach consists of four steps: (1) γ-tosylation, (2) thioetherification, (3) sulfonylation, and (4) mild alkali treatment. The degradation products were extracted consecutively with Et 2 O, EtOAc, and THF for the lignin removal, and thus the residue was enriched in LCCs. The residue was characterized by HSQC-NMR. Results indicated that the residue contained xylan and β-β substructures, although lignin was degraded. It can be concluded that the β-β substructures play an important role in the bonding sites between lignin and xylan of Eucalyptus globulus .

The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine ( Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na + ]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na + ] was controlled by the addition of either Na 2 CO 3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (M w ) of dissolved lignin increases gradually as function of cooking time. An increase of [Na + ] in the cooking liquor leads to M w decrement. Findings from cooks with constant and varying [Na + ] imply that the retarding effect of an increased [Na + ] on delignification is related to the decrease in lignin solubility at higher [Na + ].

Four common species of Dalbergia genus ( D. bariensis, D. oliveri, D. cochinchinensis, and D. retusa ), which are traded as “Rosewood” or “Hongmu” commonly throughout East and Southeast Asia, were extracted with ethanol-benzene and the extractives were analyzed by means of three IR spectroscopic methods aiming at their chemotaxonomic differentiation. Conventional FTIR and 2 nd derivative IR (SD-IR) showed defined spectral ranges, where the differences are pronounced. Two-dimensional correlation infrared (2D-IR) spectroscopy revealed significant auto-peaks suitable for reliable differentiation of the four Dalbergia species. The gas chromatography-mass spectrometry (GC-MS) evaluation of the extractives was also useful. It can be concluded that the analysis of the extractives is the best chemotaxonomic approach for identification of anatomically similar wood species.

Taiwania ( Taiwania cryptomerioides Hayata) is one of the economically important tree species indigenous to Taiwan. Hundreds of secondary metabolites have been identified from its wood, bark, root, and needles with lignans as the dominant ones. This substance group contributes a lot to the color, durability, and bioactivities of Taiwaniana. The present paper is dedicated to the quantification of radial and longitudinal lignan distribution. The extractives begin to accumulate largely in the transition zone (TZ), and reach a maximum after finishing the heartwood (hW) formation. Both dibenzyl-γ-butyrolactone type and arylnaphthalide type lignans were found in sapwood (sW) except for the compound taiwanin A. Clearly, the heartwood formation of Taiwania differs from the hitherto known hW formation types and it is suggested to be denominated as Taiwania-type hW formation, where the biosynthesis of extractives begins in the sW and where their accumulation is clearly elevated in the TZ. A generalized biosynthesis scheme of Taiwanin is presented showing the putative relationships among the most important dimeric lignans that lead to the formation of taiwanin type lignans.

To improve the solubility of cellulose at lower temperatures, several polar organic solvents were examined as cosolvents in imidazolium ionic liquid (IL). All tested cosolvents increased the solubilization efficiency of ILs at lower temperatures. Among these, N -methylimidazole, N -methyl-2-pyrrolidone, and dimethyl sulfoxide (DMSO) were notably efficient; in case of Avicel the solubility was increased, with 12–15% cellulose dissolution in 1-allyl-3-methylimidazolium chloride ([Amim]Cl) at 30°C. IR spectra of the regenerated celluloses from IL/cosolvent systems showed characteristic features of cellulose II and/or amorphous cellulose. Thermogravimetric analyses showed significantly higher thermal stability of regenerated cellulose from [Amim]Cl/DMSO compared with that without DMSO. Moreover, dimethylacetamide (DMAc) increased the solubility of filter paper pulp in 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), with 12% pulp dissolution at 30°C. No decrease in the degree of polymerization (DP) of cellulose was observed with [Emim]OAc/DMAc, whereas 8–9% DP decrease was observed with [Emim]OAc, even at 30°C. These results indicate that some cosolvents including DMSO and DMAc increase solubilization efficiency and have superior cellulose-protective effects during enhanced dissolution in ILs.

The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which the nanoparticulate titanium dioxide (TiO 2 ) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate (mWP) method, resulting in advancing and receding contact angles as well as sorption behavior of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behavior. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

This study is aiming at the simulation of wood compression (C) at a macroscopic level by means of a three-dimensional finite element analysis (3D-FEA) of solid wood and evaluation of the capability and limitations of this approach. C-Tests were carried out on Douglas fir according to ASTM D 143. The specimens included the 25×25×100 mm 3 cuboid bars for longitudinal (L), radial (R) and tangential (T) directions and the conventional 50×50×150 mm 3 blocks for the perpendicular to grain (⊥) direction. Two sets of wood parameters were developed and the 3D-FEA was implemented for the two types of specimens. The 3D-FEA worked successfully provided that the stress state coming from the total wood C was uniform. However, in case of the dominance of local compressive behaviour such as bearing, crushing and fibre shear, a microscopic-level modelling technique is needed for correction of the material parameters. More details on the limitations and difficulties of 3D-FE implementation for wood were discussed.

The viscoelasticity of Chinese fir ( Cunninghamia lanceolata [Lamb.] Hook.) during moisture desorption processes were examined at 30°C and two relative humidity (RH) modes: RH ramp-down mode from 85 to 0% RH, and RH isohume mode at 0, 30, and 60% RH, respectively. Dynamic viscoelastic properties were determined in a multi-frequency range of 1, 2, 5, 10, and 20 Hz. In both RH modes, desorption of water resulted in increasing stiffness and decreasing damping. The reduction in moisture content caused an unstable state in the cell wall due to the formation of free volumes in cell wall and rearrangement of hydrogen bonds within the polymer networks. Higher ramping rates resulted in greater destabilization, and the unstable state was more pronounced at a lower frequency. The ratio of storage modulus at 1 and 20 Hz remained unchanged during both RH modes. The ratios of loss modulus and loss factor at 1 and 20 Hz increased during the RH ramp-down and decreased during the RH isohume period. The changes of loss modulus or loss factor ratios at two frequencies were suitable for evaluation of the unstable state. The instability was aggravated with reducing RH and slightly recovered at constant RH.

The goal of the current study was to investigate the physical and mechanical properties of mycowood as a high quality tone-wood, obtained from Norway spruce by treatment of the white rot fungus Physisporinus vitreus as a function of the treatment time. In focus was the stiffness to weight ratio, which is often considered a main criterion for tone-wood selection. The vibro-mechanical properties were tested by non-destructive methods. The change of color and density were also measured after 4–12 months of fungal incubation. Density decreased up to 5% after 12 months of fungal treatment. Sound velocity was measured in small size specimens by means of the free-free vibration approach, while in large specimens the air-coupled ultrasound method was applied. The two techniques gave similar results and indicated that the sound velocity decreased in mycowood. Internal damping was increased in mycowood to a higher extent than the reduction in the specific modulus of elasticity (E/ρ) and thus the sound velocity in the material. The sound velocity was decreasing with increasing incubation times and scattering of data with this regard was larger in the transversal than in the longitudinal direction. The sound radiation coefficient and the characteristic impedance were enhanced in mycowood and its color was more brownish and richer in tone.

The static and fatigue bending behavior of wood-fiber-based tri-axial engineered sandwich composite panels (ESCP) has been investigated by four-point bending tests. Fatigue panels and weakened panels (wESCP) with an initial interface defect were manufactured for the fatigue tests. Stress σ vs. number of cycles curves (S-N) were recorded under the different stress levels. The primary failure mode in the fatigue tests was observed in the shear zone (epoxy debonding), which was different from face failure in the pure bending zone for the static bending test. For residual bending (RB) test, epoxy debonding failure occurred between the pure bending zone and shear zone. Macro cracks along the core/face interface developed as the number of cycles increased during the fatigue life. The crack propagation or damage for the panels submitted to fatigue test can be described as a three-stage damage process of first non-linear portion, followed by linear damage accumulation, and lastly non-linear accelerated damage. Bending stiffness degradation at the higher load level had faster degradation during fatigue life. The dissipated energy of the panels was small due to the high stiffness of the materials.

Vinyl ester of 4-carboxyphenylboronic acid has been synthesized and tested as reactive reagent for permanent fixation of boron in wood based on an improved approach described previously. The essence of the method is a covalent incorporation of the boron compound via transesterification between wood hydroxyl groups and vinyl ester containing boron. The synthesis of this vinyl ester was accomplished by exchange reaction of vinyl acetate with 4-carboxyphenylboronic acid. The obtained vinyl ester of carboxyphenylboronic acid was characterized by FTIR and 1 H-, and 13 C-NMR spectroscopy. The covalent fixation of boron to wood’s hydroxyl groups was achieved through potassium carbonate (K 2 CO 3 ) catalyzed transesterification of the vinyl ester containing boron. The transesterification was confirmed by weight percentage gain (WPG) calculation, curcumin staining, FTIR, and 13 C CP-MAS NMR spectroscopy. The efficiency of the reaction improved with increasing temperature and reaction time.

For decades, wood scientists and preservative formulators have employed the monocultured soil bottle assay to test efficacy of wood treatment in the laboratory as a rapid predictor of field performance. This study examines the effects of bicultured soil bottle assays on the decay by common wood decay fungi. Mycelial interactions were noted in early stages of colonization. With only two exceptions, a single fungus was apparent in each soil bottle, indicating dominance. The dominant fungi were not always the most efficient wood rots, and the rot type, white or brown, did not affect the dominance outcome on the preferred wood type.