Volume 79, Issue 2-3

Silvicultural practices, particularly planting density (PD), significantly affect the wood quality of plantation-grown trees by influencing the age of transition from corewood to outerwood. Determining transition age (TA) is challenging. Near infrared hyperspectral imaging was used to assess the age of transition from corewood to outerwood in Douglas-fir ( Pseudotsuga menziesii ) grown under different PD. Wood samples were taken from permanent research plots with six PD ranging from 2,990 to 248 stems/hectare. Twenty trees were destructively sampled at age 25, and wood discs were collected at 10 % of total tree height. Pith-to-bark radial strips obtained from each disc were scanned using a compovision hyperspectral imaging system (1,002–2,350 nm). Partial least square discriminant analysis (PLS-DA) models were fitted to approximate TA using hyperspectral data representative of corewood and outerwood. PD influenced TA and the duration over which it occurred. Average age of transition was estimated to vary from 10 (closest spacing) to 14 years (widest). Closely spaced trees exhibited an abrupt transition, while widely spaced trees had a more gradual transition. However, PLS-DA likely underestimated the transition duration for widely spaced trees, as their average ring densities did not yet match those typical of outerwood based on X-ray densitometry data.

This study developed wood composition analysis by integrating nonlinear techniques, the first derivative as a mathematical pretreatment, and a Box-Behnken design to reduce the sample size for predictive models in downed timber characterization. Utilizing 15 out of 176 core samples subjected to a year of natural degradation, models exhibited comparable efficiency to full set models reported in the literature. Spectral pretreatment highlighted the efficacy of the first derivative and smoothing, achieving a balanced distribution of explained variance. Support vector machines (SVM) models, particularly the polynomial kernel, demonstrated competitive performance compared with other reports in the literature. Coefficients of determination ( R 2 ) and root mean square errors (RMSEC and RMSEP), revealed the performance of the cellulose, hemicellulose, and lignin models. The cellulose model exhibited the best performance, followed by hemicellulose and lignin. The best-performing kernel was the polynomial kernel with R 2 values of 0.92, 0.77, and 0.74 (cellulose, hemicellulose, and lignin, respectively). The RMSEC were 1.21, 0.94, and 1.43, respectively. The RMSEP were 2.22, 1.31, and 0.47, respectively. Utilizing a reduced sample size and spectral pretreatment yielded competitive results, showcasing its potential for efficient wood composition prediction. These findings open avenues for streamlined, resource-efficient wood characterization, with implications for biorefineries and the circular economy.

Determining the creep compliances of orthotropic composite materials requires experiments in at least three different uniaxial and biaxial loading directions. Up to date, data respecting multiple climates and all anatomical directions are sparse for hygro-responsive materials like Norway spruce. Consequently, simulation models of wood frequently over-simplify creep, e.g., by proportionally scaling missing components or neglecting climatic influences. To overcome such simplifications, an automated computer-controlled climatized creep rack was developed, that experimentally assesses moisture-dependent viscoelasticity and mechanosorption in all anatomical directions. The device simultaneously measures the creep strains of three dogbone tension samples, three flat compression samples, and six Arcan shear samples via Digital Image Correlation. This allows for ascertaining the complete orthotropic compliance tensors while accounting for loading direction asymmetries. This paper explains the creep rack’s structure and demonstrates its use by determining all nine independent creep compliance components of Norway spruce at 65 % relative humidity. The data shows that loading asymmetry effects amount up to 18 %. Furthermore, the found creep compliance tensor is not proportional to the elastic compliance tensor. By clustering the compliance components, this work identifies four necessary components to represent the full orthotropy of the compliance tensor, obtainable from not less than two experiments.

Partial sealing of surfaces of test specimens is essential for determining direction-dependent water absorption of wood. Preliminary tests with existing sealants showed limited applicability particularly for standardisation. The objective was to find new sealer material. The suitability of four different materials (bitumen, polyurethane acrylic resin, liquid rubber spray, aluminium tape) was investigated. Their sorption capacity and water vapor tightness were determined with an automated sorption balance. The experiments revealed that most of the used sealers were not diffusion-tight or showed outgassing. Only the aluminum tape seems to be suitable.

Heat-treated wood is widely used for outdoor furniture manufacturing. However, it is susceptible to against physical degradation such as cracking and discoloration. This study involved heat-treated wood at three different temperatures of 180 °C, 200 °C and 220 °C was acetylated using vacuum-pressure impregnation methods to enhance photostability, dimensional and thermal stability. The laboratory chromaticity data indicated a substantial enhancement of the photostability of the acetylated heat-treated wood. The color difference was reduced from 11.89 to 10.08 for the 180 °C treatment, then from 10.24 to 9.02 for the 200 °C treatment, and from 8.31 to 8.11 for the 220 °C treatment compared to unmodified wood at the same temperature. The microstructure analysis and chemical composition study suggested that the hydroxyl groups were greatly reduced, rendering the microstructure and chemical composition of wood relatively stable. In addition, the results of water contact angle, water absorption, swelling and shrinking data show that acetylated wood exhibits lower hydrophilicity and greater dimensional stability. Thermo-gravimetric analysis reveals that acetylated wood maintained better thermal stability, as evidenced by the greater maximum temperature for thermal degradation. The weathering resistance of heat-treated wood was significantly improved by acetylation treatment.

This study aimed to evaluate the preservative potential of extracts from teak wood industrial waste against artificial weathering and decay fungi. Teak extracts were obtained in hot water, acetone, ethanol and methanol and tested against brown-rot ( Rhodonia placenta , Gloeophyllum trabeum , Neolentinus lepideus ) and white-rot fungi ( Irpex lacteus ). Aging tests included the leaching test and artificial weathering in a QUV accelerated weathering tester. The chemical analysis of the extracts was carried out by gas chromatography-mass spectrometry (GC-MS), and the compounds were compared with the cited literature. The extracts were characterized as quinone derivatives (35 %), mainly tectoquinone (28 %), followed by squalene (8–12 %) and other phenolic compounds (6 %). Lapachol, although found in proportions of 0.7–0.9 %, plays an important role in wood durability and biocidal activity in teak extracts. The results obtained by the chemical analysis indicated that the main compounds identified in this study can act synergistically on the resistance of wood impregnated. Teak extracts ensured high resistance to the decay fungi tested and results showed better performance of acetone extracts. In view of the results obtained, it is recommended to carry out other tests (soil bed and field tests) to verify the long-term effects of the extracts.

Electric double-layer capacitors (EDLCs) are promising devices for sustainable energy storage. However, EDLC components, such as separators and electrodes composed of activated carbon and conductive additives, are derived from fossil resources. To reduce this dependency, an EDLC was assembled using a separator and electrodes derived from hardwood kraft lignin, while still relying on fossil-based carbon black (CB) as the conductive additive. To achieve more sustainable EDLCs, this study developed all the conductive carbon, separator, and electrodes from softwood kraft lignin (SKL). When SKL was carbonized at 900 °C, it showed poor electrical conductivity and was unsuitable as a conductive additive. The carbon structures became more ordered with higher temperatures, and SKL-carbons prepared at 1,300–2,000 °C showed comparable conductivity to CB. The EDLCs with 1 wt % of these SKL-carbons exhibited higher capacitance and energy density than reference EDLCs with 1 and 5 wt % CB. Furthermore, a turbostratic (T) structure formed at 2,500 °C, enhancing conductivity and EDLC performance. SKL-carbon prepared at 2,800 °C exhibited a graphite structure in addition to the T structure, achieving the highest conductivity (0.54 S cm⁻ 1 ), but the resulting EDLC showed low power density. Thus, SKL-carbon prepared at 2,500 °C was the best conductive additive for EDLCs.