Abstract To supplement data on the parallel-to-grain tensile properties of aged timber under different loading rates, non-standard small-sized specimens were prepared from 300-year-old Tibetan Populus cathayana . Tensile tests were conducted on specimens sawn in radial and tangential directions at loading rates from 0.25 to 6 mm/min. The effects of loading rate on tensile strength, modulus of elasticity (MOE), and Poisson’s ratio were systematically analyzed. Results indicated that loading rate had a generally minor effect on MOE and tensile strength, with both exhibiting low coefficients of variation. MOE was insensitive to loading rate within 0.25–6 mm/min. Although mean tensile strength showed little overall difference, it fluctuated only slightly and non-significantly as rate increased, with a local maximum at 0.75 mm/min and a minimum at 1.25 mm/min. The tensile strength of tangential specimens was significantly higher than that of radial specimens, while MOE and Poisson’s ratio showed no significant difference between the two orientations. The obtained parameters provided basic reference data for research on Tibetan ancient timber structures.
Abstract Changes in the viscoelastic properties of wood in the intermediate-humidity range during moisture sorption have been attributed to hemicellulose softening, primarily based on the softening behavior of isolated hemicellulose. This study examined whether the loss modulus ( E ″) peak observed in this humidity range corresponds to frequency-dependent mechanical relaxation of cell-wall polymers and aimed to identify the components involved. The effects of drying history, conditioning period, measurement frequency, wood species, and component-removal treatments on E ″ during the moisture sorption process were investigated. The E ″ peak in the intermediate-humidity range was shown to be a superposition of two relaxations: (1) frequency-dependent relaxation occurring at higher humidity (approximately 60 %RH at 0.1 Hz), in which the molecular state altered by drying history persists as equilibrium is approached; (2) relaxation occurring at lower humidity (approximately 40 %RH) that disappears with time after drying. The latter relaxation remained after hemicellulose removal but was altered by delignification, suggesting the involvement of lignin.
Fast-growing hardwoods are increasingly used in Japan. However, their early deterioration under outdoor weathering conditions remains poorly understood. This study investigates the initial microscopic anatomical changes and surface color variations in Toona sinensis, Choerospondias axillaris, and Alnus japonica after outdoor exposure. Weathering was conducted from September 28 to December 11, 2020, with specimens installed facing south at a 45 degrees angle. Low-vacuum scanning electron microscopy (LV-SEM) was used to observe transverse, radial, and tangential surfaces. Color changes were quantified using CIELAB parameters (L*, a*, b*), while chemical and structural changes were evaluated by ATR-FTIR and X-ray diffraction. The key novelty is the LV-SEM-based comparative observation of the same anatomical positions before and after exposure, without coating or ion sputtering, thereby avoiding high-vacuum artifacts. Results showed consistent surface deterioration across species, with species-dependent differences in cell separation, deformation, and micro-cracking. ATR-FTIR and XRD analyses confirmed chemical degradation of amorphous cell-wall components. All species exhibited a decrease in L*, while variations in a* and b* reflected differing chemical degradation pathways. These findings clarify species-specific early-stage weathering mechanisms and provide baseline information for future long-term outdoor durability studies.
Abstract This study examines the impact of precipitation conditions, specifically pH and temperature, on the production of Eucalyptus kraft lignin from black liquor, focusing on the resulting chemical properties. Additionally, the process of hydroxymethylation of lignin during precipitation in a single step was investigated. Lignins were characterized using wet chemical analyses, which included the determination of phenolic hydroxyl group content, carboxylic group content, syringyl-to-guaiacyl ratio, molecular weight distribution, and glass transition temperature. Additionally, ATR-FTIR spectra were recorded, and prediction models between these spectra and lignin descriptive parameters were established: phenolic OH content, carboxyl group content, S/G ratio, glass transition temperature, and molecular weight distribution. The results demonstrate that the properties of the precipitated lignin are influenced by both pH and temperature during precipitation, with the precipitation yield exhibiting the most pronounced variation. The study also concludes that lignin activation during precipitation is achievable, with the most favourable outcomes observed at pH 9 and 80 °C.
Abstract TiO 2 was magnetron-sputtered on wood to achieve ultraviolet (UV) resistance and photocatalysis. In this study, Populus tomentosa Carr was used as the substrate. The wood was treated with either polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS), then deposited nano-TiO 2 films onto their surfaces via magnetron sputtering to fabricate nano-TiO 2 -coated wood. The microstructure, surface morphology, ultraviolet aging resistance, and photocatalytic performance of the nano-TiO 2 -coated wood samples were systematically characterized. The results show that after 90 min of magnetron sputtering, smooth, continuous, and dense amorphous nano-TiO 2 films were formed on both TiO 2 /PVA/wood and TiO 2 /PDMS/wood surfaces, with Ti mass fractions surface were 35 wt% and 38 wt%, respectively. After 110 h accelerated UV ageing, the total color differences (Δ E* ) of TiO 2 /PVA/wood and TiO 2 /PDMS/wood were 6.43 and 3.79, corresponding to 76 % and 87 % reductions compared with unsputtered sample, indicating excellent light stability. After 120 min of UV irradiation, methylene blue was catalytically degraded to 65 % and 48 % of its initial concentration, demonstrating good photocatalytic activity. In summary, magnetron sputtering deposition of nano-TiO 2 onto wood produces functional wood materials with enhanced UV aging resistance and photocatalytic properties. This work provides new insights for wood functional modification, indoor air purification, and green building material applications.
