Volume 75, Issue 5

The establishment of agroforestry systems (AFS) is a consistent strategy to integrate sustainable supply of wood, food and environmental services in a single land plot. Teak ( Tectona grandis Linn. F.) is an interesting option for the tree component in AFS, though there is a lack of information on its potential. This study aimed to characterize the quality of teak wood produced in an AFS regarding its technological characteristics and best end uses. Wood was sampled from a multi-stratified AFS located in the midwestern region of Rondônia state, Brazil, more specifically in a formerly deforested area of Amazon rainforest. The AFS is composed of double-ranked perennial crops and the forest component has growing space of 5.0 × 2.5 m. Physical-mechanical properties of teak wood were assessed and the results indicated its medium to high dimensional stability along with mechanical performance very close to that determined for wood from either homogeneous plantations or natural forests. Specific strength was significantly higher than some tropical wood species with higher densities. Teak wood from the AFS reached the minimum requirements for structural applications, with suitable properties to be used in the manufacture of decks, partitions and, residential flooring.

Although visible and near-infrared (Vis-NIR) spectroscopy can rapidly and nondestructively identify wood species, the conventional spectrometer approach relies on the aggregate light absorption due to the chemical composition of wood and light scattering originating from the physical structure of wood. Hence, much of the work in this area is still limited to further spectral pretreatments, such as baseline correction and standard normal variate to reduce the light scattering effects. However, it should be emphasized that the light scattering rather than absorption in wood is dominant, and this must be effectively utilized to achieve highly accurate and robust wood classification. Here a novel method based on spatially resolved diffuse reflectance (wavelength range: 600–1000 nm) was demonstrated to classify 15 kinds of wood. A portable Vis-NIR spectral measurement system was designed according to previous simulations and experimental results. To simplify spectral data analysis (i.e., against overfitting), support vector machine (SVM) model was constructed for wood sample classification using principal component analysis (PCA) scores. The classification accuracies of 98.6% for five-fold cross-validation and 91.2% for test set validation were achieved. This study offers enhanced classification accuracy and robustness over other conventional nondestructive approaches for such various kinds of wood and sheds light on utilizing visible and short-wave NIR light scattering for wood classification.

Young’s modulus in the longitudinal direction was measured by a longitudinal vibration (LV) test on western hemlock specimens with various length/width ratios. The effects of the configuration and orthotropy of the specimen on the measurement of Young’s modulus was investigated through subsequent finite element (FE) calculations. The experimental results suggested that Young’s modulus could not be obtained accurately when the length/width ratio of the specimen was in a certain range. The FE calculations revealed that Young’s modulus in the transverse direction and Poisson’s ratio in the length-width plane, as well as the length/width ratio, affected the Young’s modulus value. However, the results showed that when the length/width ratio of the specimen was larger than 10, Young’s modulus could be measured accurately with the LV test with a reduction in the effect of orthotropy.

Anisotropic shrinkage is a typically feature in wood, which is of critical importance in wood drying. In this study, the shrinkage strains over each growth ring were determined by a full-field strain measurement system during moisture content (MC) loss. Color maps were used to visualize the full-field distribution of displacement and shrinkage strain under different MC conditions. The variation of tangential and radial shrinkage strain from pith to bark, as well as the anisotropic shrinkage in heartwood and sapwood were studied. Both of the displacement and strain values increased as the MC decreased. From pith to bark, the tangential strains were higher at two poles as compared to the center, showing a parabolic distribution below fiber saturation point. While for radial shrinkage strain, a minor difference was observed except for the MC of 10%. An intersection between tangential and radial shrinkage ratio curve was observed at the MC of 28%. Both expansion and shrinkage in tangential direction were larger than radial counterparts, and the transformation from expansion to shrinkage occurred at the MC region of 32–28%. In addition, the shrinkage in heartwood was larger than sapwood, whereas anisotropic shrinkage in sapwood was more pronounced as compared to heartwood.

The purpose of this study was to determine the applicability of methyl methacrylate (MMA) and MMA–styrene in treating batai ( Paraserianthes falcataria ) wood. The effectiveness of the treatment was evaluated based on Fourier transform infrared spectroscopy (FTIR) analysis, physico-mechanical properties of the treated wood, and moisture sorption isotherm using dynamic vapour sorption (DVS) apparatus. Physico-mechanical properties of the modified batai wood were improved. The MMA-treated batai wood showed better improvement in terms of physical and mechanical properties compared to the MMA–styrene-treated batai wood. The equilibrium moisture content (EMC) for untreated batai wood was higher than that of treated samples. At 95% RH, the EMC for untreated batai wood was 20.7%, whereas the EMC for MMA- and MMA–styrene-treated samples was 7.9 and 8.8%, respectively. The findings indicate that the modified batai wood absorbed less moisture compared to the untreated batai wood. Moreover, the untreated batai wood had larger hysteresis loop than the treated batai wood. The highest hysteresis value was observed at 80% RH for untreated batai wood (3.8%), followed by MMA–styrene-treated batai wood (1.7%) and MMA-treated batai wood (1.2%). Both MMA and MMA–styrene proved to be effective treatments for batai wood because they reduced its hygroscopicity.

Esterified phenolics occur as γ -linked lignin acylations in many plant taxa but little is known about the distribution or function of such groups. In the family Salicaceae, p -hydroxybenzoate groups are present in the lignin of poplars ( Populus spp.) and willows ( Salix spp.). In this study, the distribution of cell wall-bound p -hydroxybenzoate was examined in different tissue and cell types of poplar and willow trees. This analysis showed that p -hydroxybenzoate groups were most prevalent in juvenile stems, and were elevated in tension wood and following nitrogen fertilisation. Closer examination of stem cross-sections using time-of-flight secondary-ion mass spectrometry (ToF-SIMS) directly showed that p -hydroxybenzoate groups occur predominantly in the cell walls of fibres and are largely absent from vessel elements. These results point to a role for ester-linked groups in modifying the syringyl-rich lignin of fibres, perhaps to strengthen the cell walls of these structural elements or to increase lignification rates.

Lignin nanoparticles (LNPs) from lignocellulosic biomass are expected to become promising basic building blocks for various applications in the development of multifunctional nanocomposites. Facile green preparation of LNPs and their application in polyvinyl alcohol (PVA) composite films were studied in this paper. LNPs were produced by performing fractionation of wheat straws at less than 80 °C with a recyclable hydrotropic, aqueous p -toluene sulfonic acid ( p -TsOH). The dissolved lignin could be simply separated as LNPs by diluting the spent liquor (SL) to below the minimal hydrotropic concentration (MHC) of 11.5%. The resulting LPNs exhibited an oblate spheroid morphology and a uniform particle size distribution. After introducing the available LNPs into the PVA matrix at 6% loading, the nanocomposite products could block 100 and 95% of UV light at 315 and 400 nm, respectively, and exhibited 80% antioxidant activity. In addition, the respective maximum TS and TM were 59.7 MPa and 2.07 GPa, respectively, which were increases of approximately 36 and 104% compared with those of pure PVA film. The LNPs/PVA nanocomposite films displayed improved UV resistance, mechanical properties, thermal stability and antioxidant activity and could be used as additional multifunctional agents in the fields of biodegradable plastics, tissue engineering and UV-protective biobased materials.

Mass loss (ML) of wood caused by thermal degradation is one of the most important features of the thermal treatments and referred to as an indicator of intensity and quality of the process. The ML is proportional to the quantity of the effective heat power exchanged during the treatment process, represented by the area of the temperature profile versus time during the process. In this paper a model for the ML prediction based on the relative area was discussed. The model proposed an analytical solution to take into account the non-linear trend of ML when plotted versus temperature and time as observed in isothermal experiments. The model was validated comparing calculated and measured final ML of samples treated during thermal modification tests with different temperature profiles. The results showed that the relative area calculated in a transformed time-temperature space improves the correlation with the measured ML.

The dimensional instability and inferior mechanical strength of radiata pine ( Pinus radiata D. Don) limit its use in musical instruments. To improve its properties, a two-step treatment by furfuryl alcohol (FA) and tung oil (TO) were used involving impregnation of FA precursor solution into the wood matrix, forming a highly cross-linked resin, followed by a modification with TO. Examination using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy revealed that FA resin was attached in cell walls and lumens, and the solidified TO in cell lumens and occluded pits. The incorporation of FA resin reduced the wood swelling coefficient by over 70% and the hydrophobic solidified TO decreased wood water uptake by over 80% enhancing wood dimensional stability. Although FA resin improved the modulus of elasticity and hardness of the wood, the modulus of rupture and impact bending strength were reduced. However, the additional TO impregnation step improved the modulus of rupture, impact bending strength, and wear resistance of the furfurylated wood. The performance of FA and TO treated radiata pine wood was better than that treated with FA or TO alone, and could meet the performance requirements of wood used for fretboard of string instruments.

With the growing popularity in digital systems and electronic communication equipment, there is an urgent need to develop lightweight, green, and efficient electromagnetic interference (EMI) shielding materials to handle the increasingly serious problem of radiation pollution. Herein, Ti 3 C 2 T x (MXene)/natural wood (NW) composites were prepared using a vacuum-pulse impregnation method and characterized by Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS) analysis, and EMI shielding performance. As demonstrated, Ti 3 C 2 T x nanosheets were successfully inserted into wood matrices, and hydrogen bonding between Ti 3 C 2 T x nanosheets and cellulose nanofibers induced the fabrication of Ti 3 C 2 T x /NW composites. Ti 3 C 2 T x /NW composites exhibited excellent EMI shielding effectiveness (SE) values of 28.2 dB at the X-band frequency.