Volume 73, Issue 2

The objective of this study was to understand better the cutting forces and chip formation of Scots pine ( Pinus sylvestris L.) with different moisture contents (MCs) and machined in different cutting directions. To that end, an orthogonal cutting experiment was designed, in which Scots pine was intermittently machined using a tungsten carbide tool to produce chips. The cutting forces were measured and the chip shapes were quantitatively described. Four conclusions can be drawn: (1) with increasing MC, the average cutting forces initially decreased and then stabilized, while the angle between the direction of the main and the resultant force continuously decreased. (2) The average cutting forces in the 90°–0° cutting direction were lower than the same forces in the 90°–90° cutting direction. (3) During machining, the dynamic cutting forces fluctuated less in the 90°–0° case. However, the dynamic feeding forces showed a decreasing trend in both the 90°–0° and the 90°–90° cases. (4) The process applied produced granule chips and flow chips, while less curly flow chips with a higher radius of curvature were more easily produced from samples with high MCs in the 90°–0° cutting direction.

In Ireland, most structural timber from Sitka spruce ( Picea sitchensis [Bong.] Carr.) is machine graded into C16 strength class. However, timber from early thinnings is mostly used for non-structural applications. There is an increased demand for structural timber, and timber from young trees could contribute to wood supply. However, this timber has lower mechanical properties than mature timber. In order to pre-sort the resource for structural application of wood from thinning, the possibilities of acoustic and density (D) measurements on young trees and logs have been investigated. The stress wave velocity (SWV) and pin penetration depth (PD) were measured on standing trees, which were then felled and cut into 10-m-long logs and subsequently into 3-m-long logs. Fundamental frequency was measured on logs. Finally, the logs were processed into boards, which were tested in accordance with EN 408 to obtain modulus of elasticity (MOE) in bending, bending strength (BStr) and D. The results showed good relationships between timber properties and acoustic and D measurements. Models for predicting grade properties of timber from thinnings are presented. Pre-sorting of young Sitka spruce trees and logs helped obtain higher C16 yields.

Natural resistance of eight wood species from Caatinga, an exclusive Brazilian biome, was evaluated according to [ASTM Standard (2005) D 2017-05. Standard test method of accelerated laboratory test of natural decay resistance of woods.]. Samples were exposed to white rot (WR) and brown rot (BR) fungi, namely to Trametes versicolor (WR), Pycnoporus sanguineus (WR) , Gloeophyllum trabeum (BR) and Gloeophyllum striatum (BR). Weight loss, specific gravity and extractive content of each wood species were evaluated. Diptychandra aurantiaca , Pterodon abruptus and Terminalia fagifolia were classified as “highly resistant”, while T. fagifolia was “resistant” to T. versicolor only. Machaerium acutifolium was resistant to all fungi. Aspidosperma multiflorum was resistant to WR fungi and Combretum glaucocarpum to a BR fungus. The species Pityrocarpa moniliformis and Swartzia psilonema were moderately resistant.

The quality of wood composites is dependent on the bondlines’ performance and their moisture resistance. The effect of moisture intrusion into bondlines is the focus of this study. The strain profile in the bondline during loading was investigated and the effects of weathering on the bondline were quantified by digital image correlation (DIC), while load deflection data were collected from lap-shear tests (LShTs). A total of 75 LShTs were evaluated including four different adhesive types with Douglas-fir wood, out of which 39 served as controls and 36 as substrates for weathering. The effect of weathering on failure load was not statistically significant. Only the bonded surface and adhesive type have significant effects on failure load, as well as the three-way interaction between the bonded surface, adhesive, and weathering, as revealed by three-way analysis of variance (ANOVA). The average effective shear moduli for the weathered samples were significantly lower than those for the control samples.

The ongoing preference for dark colours in parquet and furniture is a driving force for colour modification of bright wood species. The treatment of oak wood with gaseous ammonia (fuming) leads to dark colours, but residual ammonia in the wood may lead to bonding failures with resins, odour nuisance and thus customer complaints. The focus of the present paper is the determination and emission of remaining ammonia in fumed oak. A fast and convenient approach based on Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was developed to replace the currently applied time-consuming and complex determination procedures. The integrated area of the infrared (IR) region between 1575 and 1535 cm −1 shows a relationship with the coefficient of determination (R 2 =0.76) to the residual ammonia content determined by the micro-chamber/thermal extractor (μCTE) method. The prediction accuracy was further improved by partial least square regression calculations. Promising models with high R 2 (0.85), low root mean square error of cross-validation (RMSE-CV=1.08%) with five principal components were established and already integrated successfully into the production as input control. FTIR-ATR spectroscopy proved to be a simple and fast predictive method to estimate residual ammonia in fumed oak.

The basic properties of moso bamboo (MB) were determined according to the International Organization for Standardization (ISO) standards and its rheological behavior was studied by dynamic mechanical analysis (DMA) in the tensile torsion stress mode after plasticization with ethylene glycol (EG). Results show that the density and the apparent lignin content of MB increases and the degree of crystallinity decreases with increasing age. Storage modulus (G′) increases from 1- to 3-year-old MB, and then decreases again with age. When the bamboo culm with the inner and outer surface planed off was divided into three layers in the radial direction, the G′ of the outer layer was always higher than that of the middle and inner layers. The glass transition temperature (Tg) of MB plasticized with EG is about 10°C lower than the water plasticized ones, and the Tg of the outer and inner layers was nearly 1–2°C higher than that of the middle layer. The overall trend of basic properties and rheological behaviors seems to exhibit a discontinuity at 3 years, which might reflect the growth of MB and mainly the thickening of cell walls.

A new approach to the formation of “fullerene-like” carbon-nitrogen carbogels based on the interpolyelectrolyte complex lignosulfonate-chitosan (IPEC LSNa-CT) was developed. It was established that carbogel maintained the morphology of the precursor complex, i.e. the spherical geometry and the particle size of its main fractions (40–55 nm) were stored in the carbonizate. The influence of pyrolysis (Py) temperature was studied in the range of 500–1000°C on the structure of carbonizate. Carbogels obtained under different processing conditions have a well-developed microporous structure. The specific surface area of carbogels reduced with increasing Py temperature according to their nitrogen content. The maximum specific surface area (438.3 m 2 g −1 ) corresponds to the carbogel obtained at 600°C, while the maximum nitrogen content of this sample is 4.4%. The internal porosity of the material and the volume of supermicropores are reduced with increasing Py temperature due to the accumulation of double and triple carbon bonds in the carbogel. Apparently, the structure-forming N-atoms participate in the formation of condensed nitrogen-containing and cyclic structures as a donor of the electron pair and as such they accelerate the carbonization process.

No clear picture has yet been elaborated concerning the mechanism of lignin growth, and thus this topic is the focus of the present paper. Namely, the enzymatic dehydrogenative polymerization (DHP formation) of coniferyl alcohol (CA, as a monolignol) and three dilignols and their reaction kinetics were investigated. The dilignols [guaiacylglycerol-β-coniferyl ether ( I βO4 ), dehydrodiconiferyl alcohol ( II β5 ), and pinoresinol ( III ββ )] and CA as a monolignol [(3-OCD 3 )-coniferyl alcohol ( CA OCD3 )] were synthesized and subjected to enzymatic DHP formation. The dilignol derived from CA OCD3 could be identified by its higher molecular weight in comparison with the starting dilignols ( I βO4 , II β5 , and III ββ ). Based on the observed consumption rate of the CA and its dilignols, it was proposed that a radical transfer system exists between the dilignols, which is generated from the CA and the starting substrates.

Taiwania ( Taiwania cryptomerioides Hayata) is an indigenous conifer species of Taiwan. Various secondary metabolites of Taiwania with diverse bioactivities have been identified, and lignans are especially abundant in the heartwood (hW). In the present study, the wood of this species was separated to cambium (Cam), sapwood (sW), transition zone (TZ) and hW and their transcriptomes were sequenced. Three pinoresinol-lariciresinol reductases ( PLR s; designated TcPLR1 , TcPLR2.2 and TcPLR3 ), which are responsible for lignan biosynthesis, were cloned and their expressions in wood tissues were detected. TcPLR s had higher expression levels in Cam and sW in RNA-seq and reverse transcriptase-polymerase chain reaction (RT-PCR) results. Liquid chromatography-mass spectrometry (LC-MS) analysis of the reaction products of TcPLRs revealed that TcPLR1 can reduce (+)-pinoresinol to lariciresinol, and both TcPLR2.2 and TcPLR3 could reduce (+)-pinoresinol to lariciresinol and secoisolariciresinol.

The East Indian sandalwood, Santalum album L., is known for its fragrant heartwood and extractive oils. The increasing demand for the valuable sandalwood products has led to illegal and excessive logging, and there are other Santalum species in the commercial market as substitutes (adulterants). Improved tools for the identification of Santalum species are needed to control this situation. In this study, four chloroplast DNA (cpDNA) regions were screened ( mat K, psb A -trn H, trn K and trn L) on 35 vouchered specimens covering five Santalum species, i.e. Santalum acuminatum , S. album , Santalum lanceolatum , Santalum murrayanum and Santalum spicatum . The goal of this study was to test the species discrimination ability by means of both the TaxonDNA and neighbor-joining (NJ) methods. The results indicate that the combination of psb A -trn H +trn K gave the best performance for discrimination (100%) of the studied Santalum species concerning the discrimination ability and recovery rate. Meanwhile, six unvouchered wood specimens were retrieved and accurately identified at the species level based on the recommended DNA barcodes. The DNA barcode method is now ready for application in the monitoring of the trade of this valuable resource, and provides an effective approach for wood species identification and product authentication.

Tree stems deviating from the vertical position react by the formation of tension wood (TW) or compression wood (CW), which are called in general as reaction wood (RW), in which the cells are modified chemically and anatomically. The focus of the present work is the mechanical behavior of TW in five 37-year-old Eucalyptus species, which were grown on a planting area with an average slope of 28% leading to decentralized pith in the trees, which is an unequivocal indication of the presence of RW. TW and opposite wood (OW) samples were isolated and subjected to a compression-parallel-to-grain test. It was observed that TW is less resistant and less stiff than the OW.