Volume 71, Issue 9

Kraft lignin (KL) isolated from the black liquor of pulping has some antifungal potential. For investigation of this effect, KL was treated with laccase to form covalent bonds to green wood and the critical parameters for enzymatic grafting have been evaluated. The biocidal properties of KL could be confirmed. Growth inhibition of over 50% was found with lignin concentrations equal to or higher than 10 g l −1 . The change of wood color was evaluated based on the CIE L*a*b* color system and the data served for evaluation of the effectiveness of the KL binding to wood. The grafting reaction time was the most important variable in the impregnation process. Significant degrees of grafting were achieved in 10 min when samples were left to air dry after impregnation. The color loss was 30% after wood extraction with acetone. Higher temperatures and enzymatic pre-activation did not have a significant effect. As a conclusion, the most suitable procedure for enzymatic grafting of KL onto wood is by air-drying of the impregnated materials.

Enzymatic grafting of kraft lignin (KL) on wood surfaces is presented as a non-leachable wood protection treatment. Scots pine and European beech mini-blocks were treated with KL solution in the presence of laccase isolated from Myceliophthora thermophila and the formation of a stable interaction between wood and lignin was observed. Furthermore, the same strategy was employed to graft KL with the simultaneous entrapment of copper in the polymeric net formed. Enzymatic treatment diminished the leachability of the compounds in accordance with the EN 84 standard. The durability of the leached wood blocks was evaluated by accelerated decay tests. Samples with grafted lignin on the surface lost their antifungal activity in long-term exposure at the concentration tested. This observation is in contradiction to the preliminary tests, where KL seemed to have some biocidal activity. On the other hand, KL grafting in combination with copper entrapment improved the decay resistance and the copper leaching was reduced.

Tree barks, residues in forestry and the pulp industry, could be a rich source of novel biologically or pharmaceutically active substances. In the current work, chemical constituents of extracts obtained from stem barks of Pinus massoniana have been analyzed. A novelty is the isolation of a new ursane-type triterpene saponin, which was characterized as ursolic acid 3-O-[ β - d -glucopyranosyl (1′′→6′)]- β - d -glucopyranoside-28-O- β - d -glucopyranoside ( IV ). Moreover, three already known triterpenoid compounds ursolic acid ( I ), oleanolic acid ( II ) and oleanolic acid 3-O- β - d -glucopyranoside ( III ) are described. The elucidation of chemical structures of the isolated extractives was carried out mainly by a combination of 1D 1 H, 13 C and various 2D NMR experiments as well as by IR, UV and MS spectroscopic techniques. It is the first report about four triterpenoids found in bark of P. massoniana .

The norlignan (NorL) content in extractives of sugi ( Cryptomeria japonica ) shows a decreasing tendency from the outer to the inner part of the heartwood (hW). The hypothesis, that this effect may be due to polymerization, which aggravates NorL extraction, has been explored in the present study. To this purpose, samples were collected and extracted from the outer, middle and inner parts of the hW. Fractionation procedures of NorL-oligomers by LH-20 column chromatography were established, and the fractions were characterized by advanced analytical methods such as HPLC-SEC and HPLC combined with electrospray ionization ion trap mass spectrometry (HPLC-ESI-ion-trap-MS). Agatharesinol and sequirin C were the most abundant compounds. Several individual NorL-dimers and -trimers were detected for the first time, and four kinds of NorL-dimers and seven kinds of NorL-trimers were semi-quantitatively analyzed by HPLC-ESI-MS combined with selected ion monitoring (SIM). The oligomer contents show an increasing tendency from the outer part toward the middle and inner part of the hW, which accounts mainly for the monomeric NorL decrement in the same direction.

The mechanical properties of timber can be estimated from wave propagation velocity by measuring wave time-of-flight (ToF). However, a time-lag complicates the measurements, which produces an apparent velocity dependency on length and this species and instrument dependent property is also influenced by knottiness. This research is dealing with time-lag determination by different sensor positioning in situ ToF measurements. ToF longitudinal measurements were conducted on 120 90 mm×140 mm specimens of the coniferous species radiata pine, Scots pine, laricio pine and maritime pine. The following commercially available acoustic devices were used: Sylvatest Duo, USLab, and Microsecond Timer. The sensors were arranged for the measurement types “end-to-end”, “on the same surface” and “on opposite surfaces”. ToF data were obtained from the full-length (4 m) specimens and then from the same specimens shortened to 3 m, 2 m and 1 m in length. The in situ procedures of ToF are applicable for a reliable length determination independently from the time-lag (tL) and velocity. The differences observed by end-to-end measurements, with respect to velocity, are below 4.4%. A velocity correction factor can be deduced for each instrument, which is independent of species.

The development of phosphate bonded composites with properties comparable with those of current Portland cement bonded products has been investigated. More precisely, the focus of the study was the optimization of calcium phosphate cements in combination with wood processing residues slash pine ( Pinus elliottii Engelm.) planer shavings, Black wattle ( Acacia mearnsii De Wild.) residues, Blue gum ( Eucalyptus globulus Labill.) residues, hemp ( Cannabis Sativa L.) hurds and dried crushed sugarcane bagasse ( Saccharum officinarum L.) as well as pulp mill sludge and waste paper. A central composite design (CCD) for the response surface methodology (RSM) was applied for selection of the proper parameters. Mechanical tests were conducted on the composite products and the effect of the processing variables was evaluated based on the Pareto analysis of variance. The density of the wood-based panels ranged from 0.68 to 1.21 g cm −3 , that of the agricultural fibers from 0.59 to 1.15 g cm −3 and that of the paper pulp panels from 0.81 to 1.21 g cm −3 . The modulus of elasticity (MOE) data of the panels ranged from 1.63 to 4.92 MPa for wood, from 0.37 to 3.28 MPa for agricultural fibers and from 0.65 to 3.87 MPa for paper-pulp-based fibers. The physical properties of the composite products met the requirements for Portland-cement-bonded particleboards (EN 634-2, 2007).

Molecular simulation has been successfully applied to sorption and hysteresis studies of various nanoporous materials, revealing underlying mechanisms that neither theoretical nor experimental approaches can achieve. In this work, the grand canonical Monte Carlo approach is used in a simplified wood-water system to simulate sorption isotherms and hysteresis at 25°C and 40°C. Wood is represented by a cell wall model composed of a solid substance and evenly distributed independent cylindrical nanopores with diameters in the range of 0.6–2.2 nm. Polysaccharides and lignin pore-wall compositions are considered. Hydroxyl groups are modeled as negative energy pits attached to walls and water is represented by the extended simple point charge model. Capillary condensation in the wide hygroscopic range and metastable states are well demonstrated in the simulations, thus supporting the independent domain model discussed in the first paper of this series. The size of simulated hysteresis loops increases with pore size, less hydrophilic lignin composition and reduced temperature. The trends shown by the model are consistent with experimental findings. The larger hysteresis can be explained by more metastable states due to weaker wall-water interaction or smaller thermal fluctuation.

Lignin-based electrospun nanofibers (eNFs) were prepared and thermally stabilized at 250°C and subsequently carbonized at 1400°C. The starting blend was prepared in dimethyl formamide (DMF) solution with lignin and polyacrylonitrile (PAN), while a lignin-grafted-PAN (L-g-PAN) copolymer served as compatibilizer. The viscosity was highest of the DMF solution with PAN, and decreased for the lignin/PAN blends and additionally in presence of L-g-PAN. The uniform eNFs with clean surfaces dispose of diameters between 400 nm and 1 μm. The average diameter of eNFs decreased by the thermal treatment and at higher lignin contents in the blends. Remarkable shrinkage by carbonization was observed in all nanofibers. The successful carbonization of all electrospun carbon nanofibers (eCNFs) was confirmed by Fourier transform-infrared (FT-IR) spectroscopy. The specific tensile strength and elastic modulus of the eCNF mats from lignin/PAN blends were improved by the addition of L-g-PAN, and it can be safely concluded that it acts as a compatibilizer between lignin and PAN.

Research has been conducted on the biotic activity of eight chiral ionic liquids (CILs) with a natural component in the form of (−)-menthol with the configuration (1 R, 2 S, 5 R ) against Basidiomycetes and Fungi imperfecti. Optically active imidazolium salts were tested as follows: several asymmetric 3-alkyl-1-[(1 R ,2 S ,5 R )-(−)-menthoxymethyl]imidazolium chlorides with various alkyl substituents (from methyl to dodecyl) and one symmetric 1,3-bis[(1 R ,2 S ,5 R )-(−)-menthoxymethyl]imidazolium chloride containing two (1 R ,2 S ,5 R )-(−)-menthol substituents. Mycological tests were carried out with brown-rot and white-rot fungi, as well as with filamentous fungi, i.e. mold fungi and blue stain fungi. The new, optically active compounds demonstrated diverse effectiveness of fungicidal activity, which was dependent on the chemical structure of the functional groups. The natural (−)-menthol component, introduced as a substituent in ionic liquids, turned out to be an optically active compound with activity against wood-destroying fungi. (1 R, 2 S, 5 R )-(−)-menthol was especially active against the fungi tested. The fungicidal value of imidazolium chloride with two (−)-menthol substituents against Coniophora puteana ranged from 1.8 to 2.9 kg m −3 . The adsorption processes on Scots pine wood and resistance to water leaching were examined. The sorption properties of symmetric salts with two optical active (−)-menthol substituents fitted very well with the Freundlich adsorption model. Attenuated total reflection-infrared (ATR-IR) spectra confirmed that methylene groups of the aliphatic substituent, the ring of the heterocyclic imidazole, as well as the ether bridge of the natural (−)-menthol component were fixed in the structure of the impregnated pine wood ( Pinus sylvestris L.). The positive results encourage further investigation of the potential application of novel functional CILs (Figure 1) for wood protection.

Soil chemistry is known to have a major effect on the degradation of treated wood by basidiomycete fungi in laboratory and exterior ground-contact exposures. However, this topic received little attention from a soft-rot (SR) decay perspective. In the present paper, laboratory SR tests were performed with two different types of forest soils, which were also modified. Test samples, made of Pinus glabra (Walt.) (pine) were treated with four commercial copper/organic waterborne preservatives. In addition, soluble or particulate copper and the organic co-biocides quarternary ammonia compound or tebuconazole, were individually examined. After 19 months of soil bed exposure, moderate to severe degradation was observed in all treated samples in both soils. Surprisingly, microscopic examination showed minimal SR decay. Samples in the neutral soil had extensive tunneling bacterial deterioration and the best performance was observed with both copper/quaternary commercial formulations. Samples in the acidic soil appeared to have some white-rot and bacterial deterioration and all four commercial copper/organic formulations showed good statistically equivalent efficacy. For samples treated with only copper, the particulate copper samples performed statistically equivalent or slightly better than amine copper, while samples treated with only the organic quarternary or tebuconazole performed poorly in both soils.