Volume 68, Issue 1

Bioactive compounds of acetone-water extracts obtained from the root neck (RN) of Norway spruce ( Picea abies [L.] Karst.) have been studied for the first time. RN samples were divided into different zones and cut, and wood and bark were extracted separately with acetone-water. The extracts were analyzed by gas chromatography-mass spectrometry. The extractives have a tissue-specific distribution. Several lignans were identified in the heartwood. High concentrations (10%) of hydroxymatairesinol were found from the heartwood at the lowermost part of the RN. The inner part of the bark contained the highest concentrations of stilbene glucosides (20%), which were present in the outer bark only to a minor extent (0.2%). Pressurized hot water extraction was also applied and was found to be effective in separating lignans from biomass. Norway spruce roots and stumps are usually utilized for gaining bioenergy. The results presented here show that these abundant residual materials of forest economy may be a valuable source of highly bioactive compounds such as the lignan hydroxymatairesinol and stilbenes.

Some of the most important indoor wood-decay basidiomycetes were investigated in Erlenmeyer flask experiments, in which 50 Pinus sylvestris sapwood samples with moisture content (MC) of 16% were piled, in view of the parallel influence of wood moisture and temperature on decay in buildings. In the piles, the moisture flow from the liquid at the bottom was interrupted by a metal ring at layer 7. Laboratory incubations with Antrodia xantha , Coniophora puteana , Donkioporia expansa , and Gloeophyllum abietinum over the temperature range of 10°C–25°C showed that fungi are able to colonize, moisten, and thereafter degrade wood samples below fiber saturation, if a moisture source nearby is available. In extreme cases, mycelium grew on wood with 17.4% final MC, and wood mass loss of more than 2% occurred at 24.6% moisture.

Densification is a well-known method for improving the mechanical properties of wood. In the present study, unmodified and furfurylated wood samples were densified and submitted to cyclic water storage tests and cyclic alternating climate tests. Swelling coefficients and spring-back data were determined for the evaluation of the quality of densification. The study shows that results depend on the test method applied. Simple water storage tests do not reflect the behavior of densified wood in the high humidity range. The spring-back data of unmodified samples are more influenced by the testing method than those of the furfurylated ones.

Southern pine ( Pinus spp.) wood was impregnated sequentially with sodium montmorillonite (Na-MMT; in concentrations of 1%, 2%, and 4%) and didecyldimethylammonium chloride (in a concentration of 2%) in a two-step method to form organo-montmorillonite (OMMT) inside the wood. The impregnated samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses. Moreover, the water absorption, anti-swelling efficiency, compression strength, and surface hardness of the modified samples were investigated. In the first step, wood is impregnated with Na-MMT, and in the second step, Na-MMT is transformed to OMMT by in situ synthesis and the silicate layers of the clay are intercalated into the cell wall. As a result, the dimensional stability of the modified wood was improved as a function of increased clay concentration. The compression strength and surface hardness of OMMT-modified wood were also improved greatly compared with the untreated control.

Phenol (P) and phenol-liquefied wood (LW; Cryptomeria japonica , Japanese cedar) have been reacted with formalin and ammonium hydroxide as a catalyst to prepare alcohol-soluble phenol-formaldehyde (PF) resins named PF and LWPF, respectively. The resins prepared were dehydrated, diluted with ethanol, and impregnated into wood powders, filter papers, and cloths. The PF resin-impregnated matrix materials were then hot-pressed to form molding plates (MP) and their properties were tested. Differential scanning calorimetric (DSC) analysis shows that both PF and LWPF behave as hot-melting resins and are able to further condensation reactions to form a set resin. However, the maximal temperatures of LWPF are shifted to a higher temperature range compared with PF. MPs made with LWPF-impregnated materials have poorer performance than that of PF. However, the bending strength of MP with filter paper is 96.8 MPa, which fits the request of CNS 10559. The MPs made of filter papers have the best mechanical properties followed by MPs with wood powders and cloths.

Poplar wood ( Populus euramericana cv. “I-214”) has been impregnated by pulse dipping at 0.7–0.8 MPa for 30 min with a mixture of methylolurea and sodium silicate, and the sol modifier has been cured within the wood micropores by in situ gel polymerization by kiln drying, so that a Si-O-Si framework was formed. The treated wood acquired higher mechanical strength and its hygroscopicity was lowered. It was demonstrated by X-ray diffraction that sodium silicate crystallized within the interfibrillar region of the cell wall. Fourier transform infrared spectra showed that reactions occurred between the wood-OH, Si-OH, and N-CH 2 -OH from methylolurea to form C-O-Si and C-O-C bonds. As visible by scanning electron microscopy (SEM), the Si-O-Si framework was embedded in the pretreated wood. Moreover, SEM-energy-dispersive X-ray spectroscopy analysis revealed that the modifier formed layers from various thicknesses ranging from a thin layer on the cell walls up to big amounts filling the lumen.

In papermaking, the formation of bonds between single pulp fibers is influenced by the hardness of the fibers in their wet state. In this work, transversal hardness and modulus of pulp fibers have been studied via atomic force microscopy-based nanoindentation in dependence on relative humidity (RH). Additionally, the change in hardness of cellulose and xylan/cellulose model films was also investigated as a function of swelling in the presence of water and calcium chloride (CaCl 2 ) solution. The hardness of pulp fibers is decreasing slowly from 240 MPa at 5% RH to 90 MPa at 80% RH and exhibits a distinct decrease to 2.7 MPa at the fully wet state. The hardness in water is reduced by a factor of almost 100 compared with the dry state; therefore, a form change is easily possible and facilitates the formation of hydrogen bonds on the fiber surfaces. The investigations on the model films reveal that pure cellulose hardens in the CaCl 2 solution, compared with distilled water, whereas xylan on cellulose is becoming softer.

Wood is relatively transparent to terahertz (THz) radiation with wavelengths in the submillimeter range. This radiation has a high potential for sensing and imaging wood with a good spatial resolution. THz is especially sensitive to moisture content, fiber alignment, and density – all of which are critical in the manufacturing of wood products. In this work, a systematic study was undertaken on 46 very different wood species by means of THz time-domain spectroscopy with density determination in focus. The dielectric response of wood was modeled based on the Maxwell-Garnett effective medium theory. The dielectric function of the cell wall material was found to be extremely consistent over this large number of species with very different properties. This renders possible to determine wood density by THz time-domain spectroscopy. A strong correlation between the measured and predicted densities has been observed for all the samples investigated.

A fiber bundle composed of hollow fibrils is secreted from protoplasts of white birch ( Betula phatyphylla Sukatcher var. japonica Kan No. 8) leaves callus and the secretion is more efficient in an acidic medium containing high concentration of Ca 2+ . The influence of the Ca 2+ concentration and pH has been investigated concerning the number of cells secreted. The secreted hollow fibers were very thin. The 13 C nuclear magnetic resonance spectra indicated that the fibers are composed of linear (1→3)-β-glucan without branches (callose). The potential utilization of such unique callose fibers and their optimized production needs more investigation.

This work is aiming at the preparation of new bioactive compounds from α-pinene as starting material. To this purpose, the intermediates (disubstituted phenyl acylamino thioureas, class G ) were cyclized to dithiadiazoles (class H ). The intermediates and target compounds were analyzed by Fourier transform infrared, 1 H nuclear magnetic resonance (NMR), 13 C NMR, and electrospray ionization-mass spectrometry and elemental analysis. The bioassay experiments showed that the compounds G and H have herbicidal, fungicidal, and plant growth-regulating activities. The compounds 2,2′-dimethylphenyl thiadiazole and 3,3′-dimethylphenyl thiadiazole exhibited a growth inhibition activity of 72% and 68% against the root of rape ( Brassica campestris L.) at a concentration of 100 μg ml -1 (60–79% inhibition level). The compound 4,4′-dichlorophenyl acylamino thiourea displayed an inhibition activity of 75% against Physalospora piricola at a concentration level of 50 μg ml -1 (60–79% inhibition level).

The distribution of aluminum (Al) and other inorganic elements has been mapped at the cellular level in the mature xylem of maple by means of time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging. This method permits to image inorganic elements along with organic molecular species with high spatial resolution, and it was demonstrated that Na, K, Ca, and Mg are almost uniformly distributed in several contiguous growth rings of the air-dried wood sample. In contrast, Al was accumulated heterogeneously and intensely in the cell walls of the secondary xylem, including several growth rings, despite the long-term air-drying during storage. These results are interpreted that Al is immobilized within the cell wall, or it is closely interacted with the components of the secondary xylem. TOF-SIMS mapping also shows that Al has a tendency to be localized around vessels in the inner rings.

The objective measurement and subjective estimation of the surface quality by the consumers are important issues for furniture production and marketing. The objective of the present study is to find suitable (objective) roughness parameters that are linked to human sensation. Maritime pinewood and medium-density fiberboard (MDF) made from the same species are in focus. The roughness was measured by means of a 3D confocal profilometer and 13 independent 3D roughness parameters were computed. The quality of surfaces was modified through sanding, whereas the grit size of sand papers ranged between P60 and P320. The applied pressure and sanding time were controlled. The subjective estimation of the surface aspects was performed by several individuals through sensorial analysis. Biplots of several roughness parameters versus tactile rank revealed in the case of MDF a significant correlation to arithmetical average roughness S a and valley material component S r2 . For pinewood, the parameters arithmetical average roughness S a and texture aspect ratio S tr correlated best to tactile rank.

Polyelectrolyte (PE) complexes (PECs) are formed by the electronic interaction between cationic and anionic PEs, and a number of factors influence the forming pattern and characteristic of the PECs. In this work, a guanidine-based polymer with high cationic charge density (CD) and low molecular weight (MW) was applied for interacting with anionic carboxymethylcellulose (CMC) with low CD and high MW. To reveal the self-assembly pattern of the PEC, the turbidity of PEC and layer-by-layer (LBL) film, along with its adsorption on cellulose fibers, was characterized. The antimicrobial activity of the handsheet containing the PEC was also investigated. The charge ratio of anionic PE to cationic PE was found to be critical to the PEC stability. The roughness of the LBL film was increased and then decreased with more bilayers assembled. The isothermal adsorption indicated that the amount of adsorbed cationic PE on cellulose fibers was increased significantly by interacting with anionic CMC. The inhibition of the cationic PE on bacterial growth was not impaired by the formation of the complex. The CMC with high MW in the complex could maintain or even improve the antimicrobial efficiency of the guanidine-based polymer in handsheet.

The hygroscopic behavior of wood has a strong influence on its mechanical performance, yet the moisture gradients within the growth ring structure have not been sufficiently investigated. The main challenge is that moisture variations are coupled with strong sample deformation, which complicates the spatial referencing of moist and dry states. In this work, neutron imaging (NI) for the detection of water and digital image correlation (DIC) for the detection of local deformation were combined to calculate the local gravimetric moisture content (MC grav ) and the volumetric moisture content (MC vol ) within single growth rings. Specimens of Norway spruce [ Picea abies (L.) Karst.] were exposed to an adsorption-desorption cycle, with relative humidity (RH) steps varying from 0% (oven dry) up to 95% RH. After each acclimatization step, neutron transmission and DIC images were acquired. The local deformations determined by DIC were used to assign the corresponding dry density in the undeformed state to the compartment in a moist state and thus to calculate its MC by NI. No significant MC gradients could be found between earlywood (EW) and latewood (LW) within ±0.5% accuracy. However, strong density gradients between EW and LW can be directly correlated with MC vol . It appears that the MC in the cell wall is constant regardless of the particular growth ring position.

Local climate conditions have a major influence on the biological decomposition of wood. To examine the influence of different temperature regimes on wood decay caused by the brown rot fungus Postia placenta in wood with differing natural durability, sapwood (sW) and heartwood (hW) of Scots pine, inoculated mini-blocks were incubated for up to 10 weeks at temperatures conducive or above optimal to wood decay. We profiled mass loss (ML) and wood composition, and accompanying changes in wood colonization and transcript level regulation of fungal candidate genes. The suppressive effect of suboptimal temperature on wood decay caused by P. placenta appeared more pronounced in Scots pine hW with increased durability than in sW with low decay resistance. The differences between sW and hW were particularly pronounced for cultures incubated at 30°C: unlike sW, hW showed no ML, poor substrate colonization and marker gene transcript level profiles indicating a starvation situation. As brown rot fungi show considerable species-specific variation in temperature optima and ability to mineralize components that contribute to wood durability, interactions between these factors will continue to shape the fungal communities associated to wood in service.

Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments and numerical simulations by finite element modeling (FEM) concerning the TSt and fracture behavior of Norway spruce under various climatic conditions. Thin log disc specimens were studied to simplify the description of the moisture flow in the samples. The specimens designed for TS were acclimatized to a moisture content (MC) of 18% before TSt tests at 20°C, 60°C, and 90°C were carried out. The maximum stress results of the disc simulations by FEM were compared with the experimental strength results at the same temperature levels. There is a rather good agreement between the results of modeling and experiments. The results also illustrate the strong decrease of TSt with increasing temperature at a constant MC level.

Thermoplastic polymer composites reinforced with short plant fiber are worldwide in focus of research activities. Interfacial shear strength (IFSS) is an important indicator for evaluating the bonding quality between the fiber and the matrix polymer. However, the direct measurement of IFSS is especially difficult in the case of short fibers. In the present article, a method is proposed to this purpose, which is related to the known “fiber pulling out” methodology. In the case of single bamboo fibers, the IFSS in a polypropylene (PP) matrix was on, an average, of 5 MPa, which can be considered as weak. Scanning electron microscopy images revealed a rough inner surface in PP cavities left after fiber pulling out. This is direct evidence that a mechanical interlocking mechanism is active in the interphase between the hydrophilic fibers and the hydrophobic matrix.