Volume 77, Issue 10

Natural durability is one of the most rated features in wood end-use applications. In fact, several precious native tropical wood species produce timber of high natural durability, which is also related to long service life even for the highest hazard classes. However, selective logging is driving the existing volume of this group of species to near extinction. The remainder of the alternative species produces perishable timbers, which require synthetic chemical protection to prolong their service life but with detrimental effects on humans and the environment. Therefore, transferable durability has emerged as an alternative to gradually substitute traditional wood preservatives. From this approach, extractives from naturally durable wood species are removed and transferred to the non-durable wood species as an alternative environmental-friendly option for wood protection. Indeed, extractives from durable wood species have proven to have a deterrent effect on fungi, bacteria and termites and could be used to protect perishable wood species. Thus, this review aims to assess the prospects of developing environmentally friendly wood preservatives based on extractives sourced from highly natural, durable wood species to treat and add value to the group of perishable timbers. A step-wise analysis offers insights and challenges on (i) potential sources of extractives; (ii) effective extraction methods; (iii) extractive-based preservative formulation; and (iv) effective treatment methods for better preservative fixation for better wood protection. Accounts about the way forward for the development of extractive-based wood preservatives are also presented.

Flame-retardant impregnation and densification are two major modification techniques to improve the fire safety of wood. Here, these two techniques were combined to prepare flame-retarded wood, aiming at further fire hazard reduction. The delignated Pinus sylvestris L. was impregnated with boric acid (BA) and graphene oxide (GO) solutions, then densified to prepare densified flame-retarded wood named BGO-DW sample. The results revealed that the BGO-DW sample obtained a limiting oxygen index (LOI) value of 47.4 %. Its backside temperature after 1200 s heating was 49 % lower than that of unmodified wood. Besides, the peak heat release rate (PHRR) and total heat release (THR) values of BGO-DW sample were 72 and 62 % lower than those of unmodified wood due to its shorter pyrolysis interval and lower peak mass loss rate (PMLR), as supported by thermogravimetric (TG) analysis. The flame retardancy of BGO-DW sample could be attributed to the formation of compatible char containing C=C aromatic structure, C–O–C cross-linked structure, and boron trioxide (B 2 O 3 ) structure. These features of BGO-DW sample offer a new method to improve thermal stability, heat insulation, and flame retardancy for wood and wood-based products.

A lignin-based gel prepared by the chemical crosslinking of hardwood acetic acid lignin (AL) with poly(ethylene glycol) diglycidyl ether has been reported to shrink in water and organic solvents but swell specifically in aqueous binary solutions. In this study, the AL-based gel was also found to swell in lithium-salt-containing organic solvents, namely, liquid electrolytes. The uptake of salt solutions reached five times the dry weight of the gel. The ionic conductivity of the gel swollen with 1 M LiBF 4 in propylene carbonate or a mixed solution (1:1, v/v) of ethylene carbonate and dimethyl carbonate exceeded 1 mS cm −1 at room temperature (25 °C), suggesting that this gel can be applied as a gel electrolyte for lithium-ion batteries (LIBs). A prototype LIB was assembled with the AL-based gel electrolyte and LiCoO 2 /graphite-based electrodes and exhibited low bulk and charge transfer resistances of 4.1 and 9.7 Ω, respectively. Moreover, its initial specific capacity reached 104 mAh g −1 at a current density of 28 mA g −1 , which is comparable to that of a reference LIB assembled using a commercial polyethylene separator. These results indicate the significant potential of this lignin-based gel for application in energy storage devices.

The combination of computer technology and non-destructive testing technology can facilitate the development of forestry in a more intelligent direction. In this paper, a Shapley additive explanations (SHAP)-based method is used to analyse the importance of band features in the near-infrared spectrum of black walnut wood, which ranges from 900 to 1650 nm. The spectral data from the SHAP analysis are fed into an integrated framework of machine learning algorithms based on four different theories. In the comparison tests, three different pre-processed NIR spectral data are entered into the integrated framework. The result of the SHAP analysis shows that the wavelengths that are positively correlated with the air-dry density of black walnut are 1354.59, 1400.23, 1341.51, 1426.26, 1413.25 nm. The model predictions show that the SHAP-treated spectral data outperformed the other two treatments for each model. For the SHAP-treated spectral data, the KNN model gives the best results with an R 2 of 0.947 and an MSE of 0.0010.