Volume 13 Issue 3

The efficiency of surface pretreatment with natural essential oils relative to the weathering performance of Norway spruce wood was examined. This study investigated the combination of this pretreatment increasing biological resistance and oil-based coating with protection against ultraviolet light and hydrophobic topcoat with silicon nanoparticles during natural and artificial weathering. The coating systems were exposed to 24 months of natural weathering in climatic conditions of Central Europe and 2,016 hours of artificial weathering. The synergistic effect of a coating system based on safflower with essential oils and commercial oil-based coating was the most efficient. The application of one layer of an oil-based coating in a wet state of surface pretreatment exhibited results comparable to the application of two layers in a dry state. For all coating systems, increasing changes of colour, roughness, and surface wettability were observed, which differed according to the weathering method. Weathering performance of transparent coating systems was evaluated during both weathering tests by exact measurements, laser scanning microscopy and visual evaluation as well. Total colour difference did not prove to be a sufficient evaluation criterion to indicate coating performance during weathering.

Currently, the bending properties of glulam made from fast-growing poplar barely meet the requirements for application. In this study, the bending properties of glulam made from preservative alkaline copper quaternary (ACQ)-treated and phenol-formaldehyde resin reinforced poplar in different laminate configurations were full-scale tested via a four-point bending method. Theoretical models including stiffness model and rigidity model under different loading modes were founded based on the mechanical analysis of composite materials to predict the Young’s modulus of bending and bending strength. The Young’s modulus and bending strength of modified fast-growing poplar glulam was greatly enhanced compared with untreated ones, which can meet the standard requirements for symmetrical mixed-grade composition glulam grade E85-F255. The Young’s modulus was predicted with the rigidity model with high accuracy. The relative error was below 12%. The modified stiffness model with correction factors for normal stress and interlayer tension shearing stress can also accurately predict the failure mode and bending strength.

To elucidate the origin of shrinkage anisotropy of wood during the drying process, wood from three tree species, Quercus sp., Juglans nigra, and Pometia pinnata, was analyzed using thin cryomicrotome sections and sequential drying on a micro-scale. The data on shrinkage, based on the transverse direction, were calculated using Image Pro Plus software to measure the thickness of the cell wall of fibers. The results showed that: (1) In the tangential direction, the shrinkage of wood fibers were all in the “smallest-bigger-smaller (-bigger-smaller)” pattern from A to C (A: The cells closest to the wood rays; C: The cells in the middle between the wood rays) and fibers next to the rays always have the minimum shrinkage at different moisture contents; (2) the width of the rays has no negative correlation with the shrinkage of wood fibers; and (3) the rays have the same effect on the shrinkage of wood fiber cells in both latewood and earlywood. In addition, the shrinkage of latewood is more severe than that of earlywood, which leads to tangential shrinkage.

According to published studies, certain nonaqueous solution-based treatments can be highly effective for prolonging the useful lives of bound volumes, within which the paper had been formed under acidic papermaking conditions. Such treatments, which typically use reactive alkoxide-based organometallic compounds dissolved in low-surface-tension liquids, have been shown to decrease the tendency of the paper to become brittle during long storage or during accelerated aging. This article reviews published evidence concerning the underlying mechanisms of such treatments. Evidence suggests that dissolved alkoxides and related carbonated alkoxide-based compounds are able to react directly with acidic species within acidic paper during treatment of books. Such reactions help explain the demonstrated effectiveness of nonaqueous solution-based deacidification treatments.

To meet increasing demands for alternatives to fossil-based chemicals, environment-friendly and renewable energy materials are of great importance. Biomass-derived 2,5-bis-(hydroxylmethyl)furan (BHMF) has the potential to partly substitute petroleum-based aromatic diols during polymerization. This paper summarizes recent research on the synthesis of BHMF by the reaction of hydrogen from biomass-based 5-hydroxymethylfurfural through different reduction routes, including the Cannizzaro reaction, catalytic hydrogenation, and catalytic transfer hydrogenation. Applications of BHMF as a direct material and intermediate in fabricating polyurethane, self-healing materials, resins, and more, which utilize ring-opening, double-bond addition, and oxidation reactions, are discussed briefly. Additionally, the challenges and opportunities in the formation and application of BHMF in the future are discussed.

In recent decades, fungal roles in bioremediation of toxic contaminants such as potentially toxic elements (PTEs) residing in soil, waste water, and landfills have been studied. Bioremediation is an alternative way to deal with toxic contaminants in the environment. Some decay fungi are able to remove metals by producing metabolites, such as oxalate, which can react with metal ions and generate insoluble forms of metal:crystal complexes. Brown-rot fungi have the ability to produce extracellular oxalate in significant amounts, and this is closely related to chelation of copper by precipitating to copper oxalate crystals. Copper-tolerant brown-rot fungi have a potential role in a bioremediation system by depolymerizing the structure of wood treated with copper-based wood preservatives and adapting to copper through increased oxalate production and formation of copper oxalate crystals. The focus of this review is to suggest that copper-tolerant brown-rot fungi could be a viable option for use in future mycoremediation practices.