Volume 79, Issue 7

In Africa, the forestry industry generates significant waste that remains underexploited. Studies have highlighted the presence of active biomolecules in durable wood species. This study characterised the extracts of three durable tropical woods: Nauclea diderrichii , Mansonia altissima , and Milicia excelsa . Moreover, we estimated their insecticidal potential. Once the wood powders samples were prepared, the extractions were carried out by cold maceration for 2 h in a hydroethanolic solvent in a 50/50 (v/v) ratio of ethanol and water. The yields for aqueous extractions (0.9 ± 1.2 % to 1.3 ± 0.1 %) were lower than those for hydroethanolic extractions (4.3 ± 0.7 % to 5.2 ± 0.8 %). Aqueous extracts contained alkaloids, tannins, quinones, polyterpenes, sterols, polyphenols, flavonoids, anthocyanins, and saponins, while hydroethanolic extracts contained the same compounds but in higher proportions. Total polyphenol and flavonoid contents of the aqueous extracts were 2.2 mg GA Eq/g and 0.6 mg QEq/g, respectively, compared to the hydroethanolic extracts with contents of 93.4 ± 0.1 a mg GA Eq/g and 97.0 ± 1.1 a mg QEq/g ( p  =  0.005 ). The antioxidant activity of the aqueous extracts was 8.2 ± 0 c  µmol Trolox Eq/L, while that of the hydroethanolic extracts was 60.6 ± 0.3 a  µmol Trolox Eq/L ( p  =  0.005 ). These results suggest that the wood extracts studied contain bioactive molecules with potential applications in sustainable control of crop pests.

The aim was to evaluate the potential of the stem bark of Byrsonima spicata , Croton matourensis , Myrcia splendens , Tapirira guianensis and Vismia guianensis as a source of value-added macromolecules to contribute to the bioeconomy in the Amazon. The barks were collected from secondary forests in the state of Pará, Brazil, and analysed for the first time for anatomical and chemical composition. High-performance microscopic images showed the presence of a rhytidome composed of one to seven layers of periderms. The bark had a significant presence of extractives soluble in ethanol and water (from 29.3 to 46.1 %). Lignin content ranged from 19.0 to 33.4 %. The optical emission spectrometer showed a rich mineral composition, particularly in calcium (2.9–20.6 g kg −1 of bark). High tannin content was quantified, especially in B. spicata (19.1 %) and M. splendens (29.9 %). The composition of the bark suggests that it can be used to obtain potentially valuable phenolic compounds with chemical functionalities and bioactivities. After this extraction, the lignin-rich solid residue is suitable for a thermochemical valorisation , while the high nutrient levels make soil amendment an interesting application. A sustainable bark removal may therefore generate local income and contribute to the conservation of these Amazonian species.

This study investigates the rheological mechanisms underlying changes in the mechanical properties of wood during moisture adsorption and desorption. To approximate the net molecular momentum at a specific humidity and time, an index was established by dividing the loss tangent value under equilibrium conditions at each humidity by the loss tangent value at each time point. This approach linked the unstable microstructural behavior associated with adsorption and desorption to the stabilization of the structure over time and molecular mobility at specific conditions. This metric enabled effective tracking of molecular mobility during humidity changes and provided insights into the mechanisms driving changes in mechanical properties. During adsorption, wood transitions from a glassy state far from the rubbery state toward one closer to the rubbery state, while desorption shows the opposite trend. Results also indicated an energy barrier near the medium humidity (30–60 %RH), unrelated to lignin. Instead, the softening of hemicellulose and changes in amorphous polymer states within the cell wall likely play critical roles in these mechanical property changes.

Differences in characteristics between sapwood and heartwood of short-rotation teak are a significant obstacle to valorize mixed boards containing both types of wood. Chemical and thermal modifications are attractive methods to improve the quality of short rotation teak wood allowing homogenization of both sapwood and heartwood properties like decay resistance, dimensional stability and color. However, no data are available on the difference in density between sapwood and heartwood of short-rotation teak, as well as on the effect of such treatments to achieve homogeneity. Density profiling is important to assess the homogenization of the modification process of chemically and thermally modified wood. The objective of this study was to determine the effect of chemical and thermal modification on the density profile of sapwood and heartwood of short rotation teak from pith to the bark using X-ray computed tomography (XCT). The chemical and thermal modifications applied were furfurylation (FA), thermal modification at 150 and 220 °C, and a combination of glycerol-maleic anhydride (GMA) impregnation and thermal modification at 150 and 220 °C. XCT was used to investigate the density variation of short rotation teak wood before and after chemical and thermal modification. A registration process using Avizo software was applied to overcome the deformation effects due to chemical and thermal modification treatments. The results show that the vessel diameter increased after FA treatment due to polymer-induced swelling, while it decreased after GMA220 treatment due to vessel collapse caused by thermal effects. FA treatment increased the density of short rotation teak wood, and the density profile changes were rather uniform. There was a decrease in density due to thermal and GMA treatments, with a significant difference in density changes between sapwood and heartwood. The density profile allowed to observe the homogeneity of sapwood and heartwood density according to the applied treatment. Chemical and thermal modification showed weak effect on the homogenization of the density profile between sapwood and heartwood.

In this study, thermally modified Scots pine ( Pinus sylvestris L.) was impregnated with DMDHEU (1,3-dimethylol-4,5-dihydroxyethyleneurea) monomers combined with a flame retardant (FR) based on monoguanidine phosphate salt. Fire performance was assessed using ignitability tests (ISO 11925-2, 2020), mass loss calorimetry test (ISO 13927, 2015), and single burning item (SBI) tests (EN 13823, 2020). Results showed enhanced flame retardancy, reaching Class B in the SBI test. Small-scale ignitability tests revealed minor differences in flame spread across samples, unlike the SBI results. Fire growth rate and ignition time from mass loss calorimetry strongly correlated with burning suppression in the SBI test.