Volume 72, Issue 9

Cercidiphyllum japonicum is a deciduous tree that grows in East Asia, where its raw extracts have long been used in folk medicnes to treat various disorders or diseases. In the current work, extracts from C. japonicum twigs were studied for the first time. Seven individual compounds were isolated from the extracts, including a new galloylflavonol glycoside, namely 8-methoxykaempferol-4′- O -galloyl-3- O - α -L-rhamnopyranoside ( VII ), and six known phenolics [two anomeric galloyltannins (3,4,6-tri- O -galloyl- β -D-glucopyranoside ( I ) and 2,2′,5-tri- O -galloyl- α/β -D-hamamelose ( III )), one anomeric ellagictannin, pedunculagin ( II ), one flavonol, kaempferol ( V ) and two flavonol derivatives (kaempferol-3- O - α -L-rhamnopyranoside ( IV ) and 8-methoxykaempferol ( VI ))]. Structural elucidation of I – VII was conducted mainly on the basis of their spectroscopic [ultraviolet (UV), infrared (IR), nuclear magnetic resonance (NMR), mass spectrometry (MS)] and physicochemical analysis, as well as by comparison of the analytical data with those in the literature. Compounds I , II , IV and VI have not yet been reported in the genus Cercidiphyllum. Compound VII , a previously undescribed flavonoid, was isolated and elucidated in this work for the first time.

Low-cost precursor fibers (PFs) were prepared from blends of a wheat straw lignin (WSL) and a commercial textile-grade polyacrylonitrile (PAN) by wet spinning, and then the precursors were converted into carbon fibers (CFs) by thermal stabilization and carbonization. The PFs were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The lignin content in the blends was found to play an important role in the PF structure, which was closely related to the change of intermolecular forces in the spinning solution. The lignin, acting as the carboxylic acid comonomer, had significantly promoted the thermal stabilization of the lignin/PAN blend PFs, which helped to further decrease the production cost of CFs. With increasing lignin contents, the carbon content of CFs remained at about 95%. The carbon of lignin could be utilized for the preparation of CFs.

Fibers of four tree species, moso bamboo and wheat straw were modified in situ with organo-montmorillonite (OMMT). The characterization of the physical and mechanical properties of the resulting composites showed that OMMT can be synthesized in situ within the fibers’ matrix. Some individual OMMT layers were clearly observed, while some agglomeration was seen on the fiber surface. After blending with poly(lactic acid) (PLA), redistributions of OMMT in the PLA matrix occurred and most properties of the composites were improved. The modification effect of Chinese fir was the best while that of moso bamboo and straw wheat was rarely poor because of their different chemical components, anatomical structures and densities. In short, a higher lignin content, large diameter of pits and lower density contributed to the improved properties of the wood plastic composites (WPCs) with the participation of OMMT.

Phenol formaldehyde (PF) resin is a well-tried adhesive for manufacturing laminated veneer lumber (LVL). PF has a high bonding strength, good cold pressing property and contributes a lot to the high production efficiency of LVL. In the present paper, PFs were synthesized at three different alkaline condition levels with a molar formaldehyde to phenol (F/P) ratio of 2.25. The bonding strength of PFs was not influenced by the alkalinity. Compared with PFs synthesized under alkalinity of 1 and 4%, PF with 8% alkalinity formed a resin with a high mole mass (MM), uniform mole mass distribution (MMD) and a high cross-linking density. With PF 8% , the cold pressing property could be shortened from 30 to 12 min in the winter time. Cured PF 8% had a higher cross-linking density than PF 1% and PF 4% . PF 8% has a high potential for industrial production of LVL.

Liquid condensates collected during drying of lumber, sawdust or wood powder are usually discarded. The objective of this study was to investigate the potential utilization of such condensates from oak, beech and walnut, focusing on those obtained in a 7.8 MHz vacuum dryer. The condensate was replaced with the deionized water (5%) in the production of urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) resins in the reactor. The technical properties of the resins and chemical properties of the liquid condensates were determined. Particleboards (PB) and middle density fiberboards (MDF) were produced from the control and modified resins. The technical properties of both modified resins were between the limit values of commercial UF and MUF resins used in the wood-based panel industry. The formaldehyde (F) emission from PB and MDF decreased significantly by incorporation of the condensates into the UF and MUF resins.

Uncured and cured urea-formaldehyde (UF cured ) resins prepared with formaldehyde/urea (F/U) mole ratios of 1.0 and 1.2 and at the catalyst levels of 1, 2 and 3% NH 4 Cl were hydrolyzed for 5, 15 and 30 min and the degradation products were evaluated using gel permeation chromatography, Fourier-transform infrared (FTIR) and liquid carbon-13 nuclear magnetic resonance ( 13 C-NMR) spectroscopies. The molar masses of the degradation products, their functional groups and structures were determined. An extended hydrolysis time and higher catalyst levels resulted in compounds with higher molar masses. Similar functional groups and distribution of chemical species were found by both FTIR and 13 C-NMR spectroscopies in the hydrolysates of UF cured , indicating water hydrolysis of hydroxymethyl groups and then methylene linkages. Methylene linkages and mono- and tri-hydroxymethyl ureas were mainly responsible for the liberation of formaldehyde from UF cured during hydrolysis. The indicated compounds are believed to contribute to the long-term release of formaldehyde from the resins. This is the first systematic report on the composition of UF cured hydrolysates.

Holes contribute to the non-homogeneous nature of solid wood and shift the neutral axis of wood beams away from the centroid. Based on the plane-section assumption and idealized trapezoidal distribution, new calculating formulas will be presented in terms of the location of neutral axis for clear beams and wood beams with a hole at the center, compression zone and tension zone. To verify the results of theoretical analysis and formulas, four-point bending experiments of wood beams were performed by a digital image correlation (DIC) technique. There is a reasonable agreement between calculated and experimental results with a hole at the center or in the compression zone of the beams. Concerning a hole in the tension zone, on the other hand, the calculated locations of neutral axis are not in agreement with the experimental results, due to the plastic behavior on both the compression and tension zones of the beams in the inelastic stage.

Bamboo sliver (BS) is a potential elementary unit for multidimensional bamboo-based composites (MBBCs). Axial tensile and flexibility characteristics of thin radial (R) and tangential (T) BSs (BS R and BS T with a thickness of 0.5–2.0 mm) have been studied. Axial tensile strength (AxTS) and modulus of elasticity (AxMOE) were positively correlated with the vascular tissue ratio (VTR), and the tensile properties of slices with 43–51% VTR increased more rapidly than in the VTR range of 20–36%. In axial tensile tests, cracks propagated along a V or Z route in BS R , while fibers were pulled out in the central section in case of BS T . AxTS and AxMOE values increased with decreasing moisture content (MC) at 6.2–16.6% below 75°C. Flexural flexibility (FF) was enhanced with increasing MC and VTR, and the effect of MC on FF was amplified with MCs below the fiber saturation point (FSP). In situ scanning electron microscope (SEM) observation during flexural tests revealed a deformation resistance of vascular tissue (VT) and the deformation disposition of parenchyma.

A near-infrared spatially resolved spectroscopy (NIR-SRS) system, also called the hyperspectral imaging system, was applied in a line scanning model combined with a concentrated halogen light source (Ø 1 mm), and spatially resolved reflectance images of Douglas fir [ Pseudotsuga menziesii (Mirb.) Franco] wood were obtained. The samples with various densities, grain directions and thicknesses were observed in the NIR range of 1000–1600 nm. Then, a nonlinear curve-fitting algorithm was applied based on the steady-state diffusion theory model to estimate the absorption coefficient ( μ a ), and reduced scattering coefficients (μ′s${\mu '_s}$) both parallel and perpendicular to the grain direction at each measurement position. The absorption scattering coefficients at 1457 nm and two kinds of reduced scattering coefficients at 1002 nm were highly correlated with wood densities measured by an X-ray densitometer. The correlation coefficients were 0.953 and 0.987 for 3 mm and 5 mm samples, respectively, while three optical profiles were combined. It can be concluded that NIR-SRS is a fast and simple method for measuring the optical characteristics of softwood, although it has a non-homogeneous cellular structure. Sub-surface density and grain direction could be predicted with satisfactory accuracy based on a few key wavelengths without relying on multivariate statistical analysis.

Thermal modification (TM) of wood at high temperatures can lead to significantly improved decay resistance against white rot (WR) fungi, but little is known about the mechanism of this improvement at the cellular level. As a contribution to this topic, hardwoods (HWs) (ash, beech) and softwoods (SWs) (spruce, fir) were submitted to the Termovuoto ® TM process at 220°C for 3–4 h (shortly TMW 220°C ) and were degraded by the WR fungus Pycnoporus sanguineus. The results were studied using microscopy techniques. Decay occurred preferentially via cell wall delignification prior to the removal of cellulose and hemicelluloses. Concerning this effect and fungal colonization, there were no essential differences between TMW 220°C and the unmodified reference of all wood species. TMW 220°C , however, showed a number of characteristic changes in decay morphology. Narrow and distinct concentric transition zones were observable in decayed fiber and tracheid cell walls, which demark the lignified and delignified regions. Moreover, cell wall separation by preferential delignification of compound middle lamellae (CML) was not seen in decayed tracheids. It can be concluded that the Termovuoto TMW 220°C process has an impact on the delignification process of P. sanguineus at the cell wall level, which slows down the decay.

The growth of oyster mushroom ( Pleurotus ostreatus ) on pulp and paper industry wastes was studied. Specifically, the question was investigated whether solid-state fermentation of P. ostreatus on paper-mill deinking sludge and primary sludge substrates is appropriate for production of enzymes, relevant to the pulp and paper industry. Following fermentation, extracellular protein was extracted and the specific activities of four enzymes were determined, namely, the cellulase, xylanase, lipase and peroxidase. Furthermore, the effects of the pH of the extraction buffer on these enzyme activities were determined, along with the effects of the incubation time. The data show that P. ostreatus can grow on solid wastes from the pulp and paper industry, which could help to minimize the waste volume and to decrease the ecological impact. Furthermore, the solid wastes in focus are good substrates for the production of commercially interesting enzymes.