Volume 76, Issue 4

Wood fire residues can be found in various stages from less damaged material, pyrolysis products (a char) to deeply damaged material (ash). Moreover, wood burning can be influenced by fire accelerators and/or flame retardants. This paper provides a brief description and evaluation of conventional and comprehensive variants of analytical techniques with examples of their various applications at analyses of wood materials and wood fire residues. They include specificities of sampling, elemental chemical analysis, thermal analysis, extraction of compounds from fire debris, chromatographic methods and mass spectrometry, spectroscopic methods, chemometrics and quality assurance.

Studies linking wood properties of the southern pines to climate parameters and/or irrigation treatments have generally used seedlings or mid-rotation age trees, the latter comprised primarily of juvenile wood. To investigate possible drought-induced effects on mature wood physical properties, densitometry data from 50-year-old slash ( Pinus elliottii Engelm.), longleaf ( Pinus palustris Mill.), and loblolly (taeda L.) pine trees were matched with annual soil moisture values. Each of two growth ring groupings per increment core had a two-year period of ample moisture followed by a two-year period of drought; these were centered at ages of 20 and 38 years. For slash pine, the latewood width was 30% lower ( p  = 0.011) for the drought period at age 20. Seemingly similar results were obtained for longleaf pine, but the probability ( p  = 0.051) just exceeded the threshold for significance ( α  = 0.05). No differences were observed for either earlywood or total ring widths. Ring specific gravity (SG) values that were 11% lower for slash pine and 7% lower for longleaf pine can be attributed to drought-related reductions in latewood formation. Unlike other studies with younger trees, both percent latewood and ring SG values for mature loblolly pine were unaffected by drought.

Bloodwood ( Haematoxylum campechianum L.) native to Central America has been known as dye source since the prehistoric times by the Maya. Nowadays, bloodwood is increasingly used for plantations but its use for furniture, flooring, or fencing is only of regional importance. The reason is seen in lacking knowledge of its properties. To expand that knowledge, this Part 1 of the two-part study series investigated the anatomy and the discolouration due to leaching of heartwood of H. campechianum . Anatomical characteristics were described qualitatively and quantitively using scanning electron microscopy and X-ray micro-computed tomography. Detailed wood anatomical data are presented, together with numerical analyses of cell parameters. Apart from wood anatomy, colourimetric analyses were obtained after 10 leaching cycles. The colour change of the wood due to water exposure was determined measuring in CIE L * a * b * colour system. In addition, the extinction of the leachate was determined spectrophotometrically after each leaching cycle. The resulting colour change was evaluated according to colour change after each cycle. The most prominent change in colour was observed for the first cycle due to leaching. Because of the extensive leaching of extractives, further investigation might address the effect of leaching of water-soluble extractives on adhesion properties of bloodwood.

Haematoxylum campechianum is most prevalently used as dyewood; its use for furniture, flooring, or fencing is only of regional importance, which might be due to lacking data about its technological properties. Therefore, small specimens were cut from H. campechianum stems from plantations in the lowlands of the Usumacinta delta in Mexico. The latter were subjected to laboratory decay and moisture studies. Water vapour sorption, liquid water uptake, and swelling of H. campechianum appeared much lower in comparison with most European grown wood species and similar to tropical hardwoods such as Tectona grandis . After removal of water-soluble ingredients, water vapour sorption of H. campechianum specimens further decreased, which assigned such ingredients a somewhat hydrophilic character. Mean mass losses (ML) due to decay by white, brown, and soft rot fungi in laboratory tests were <5%. On the basis of a dose-response model, wetting ability factors and ML values from decay tests predicted an outdoor performance similar to T. grandis and Intsia bijuga . Based on this preliminary property profile, H. campechianum can be recommended for both outdoor (e.g. fencing, outdoor decking, railing) and indoor applications (e.g. flooring, manufacturing of furniture, wall and ceiling panels, decoration artwork).

Japanese larch ( Larix kaempferi ) is an important plantation species in Japan as well as in Europe. The inheritance of wood color ( L *, a * and b *), mass loss by a white-rot fungus ( Trametes versicolor ) and a brown-rot fungus ( Fomitopsis palustris ), and polyphenol content (as the taxifolin equivalent) in heartwood were examined for 75 trees in 15 full-sib families of L. kaempferi. The mean values of all trees were 74.5 in L *, 8.4 in a *, 23.0 in b *, 18.3 and 26.0% in mass loss by T. versicolor and F. palustris , and 0.045 µmol/mg in polyphenol content. The narrow-sense heritability ( h 2 ) showed higher values in heartwood color ( h 2  = 0.70–0.87), but mass loss and polyphenol content showed relatively lower values ( h 2  = 0.00–0.33). Significant negative correlations were found between polyphenol content and mass loss by white-rot and brown-rot fungi. In addition, the polyphenol content of heartwood was significantly correlated with the color of heartwood. Similar results were obtained in genetic correlations. Thus, it is concluded that parents with lower L * and higher a * and b * in heartwood could produce progenies with higher polyphenol content in heartwood, thereby leading to higher decay resistance.

Photodegradation and decay may happen simultaneously on wood under many exposure conditions. The aim of this study was to explore the effect of photodegradation on fungal colonization during initial stage of brown-rot decay of wood. For this purpose, southern pine ( Pinus spp . ) wood was exposed to accelerated UV weathering for different durations, and then decayed by a brown-rot fungus ( Gloeophyllum trabeum ). The changes in wood microstructure, chemical composition, surface color, crystallinity, fungal colonization pathways, and photodegradation products after weathering and decay were evaluated and characterized. The results showed that both weathering and decay led to obvious color change on wood surface. The photodegradation of wood resulted in the formation of cracking in cell wall, thus creating new voids. The photodegradation products, which mainly consisted of phenols, diterpenoid acids, and other lignin derived compounds, appeared in the cell lumen. During the initial stage of brown-rot decay, fungal hyphae invaded into wood through inherent voids such as ray cells, axial tracheids, and pits, and completed the initial colonization after 20 days. After photodegradation, hyphae could also invade wood from the new voids, and the acidic photodegradation products promoted the non-enzymatic degradation process of brown-rot. However, lignin derived compounds seemed to inhibit the further activity of decay fungi.

While wood substances that contain water have shown a dielectric effect, they have never been directly proposed as a microwave absorption material to reduce artificial electromagnetic pollution. In this study, the microwave absorption efficiency of wood that contains water was investigated based on its dielectric properties in the microwave frequency range to optimize the parameters of wood unit cells, including the orientation, moisture content (MC) and thickness. Subsequently, inspired by the design concept of electromagnetic metamaterials, single-layer wood unit cells containing moisture were directly integrated into double epoxy resin layers. This procedure formed a natural wood-based metamaterial (NWM) with a simple periodic Sandwich structure without the need for further chemical modification and/or high energy consuming processes. Such design strategies allowed the NWMs to overcome the limitation of inherent dielectric properties of natural wood and present significantly enhanced microwave absorption performance, as well as different absorption behavior. NWMs at a MC ≤ 70% displayed a selective absorption mode, while NWMs at MC ≥ 85% showed a broadband absorption mode. Both absorption modes could achieve the peak absorptivity > 98%. Particularly, the NWM in the broadband absorption mode possessed an effective absorption (absorptivity > 90%) bandwidth of 9.04 GHz, which was 7.6 times that of natural wood (1.19 GHz). The NWMs performed well when irradiated by microwaves with different angles and directions. Also, the thickness of NWMs was only 7 mm, allowing easy incorporation of the materials in engineering designs. The use of sustainable materials, impressive performance, high stability, practical thickness, and the facile and cost-effective production technique demonstrated NWMs with great potential in designing green buildings.

In order to explore the application of furfurylated wood as engineering material, polyvinyl alcohol (PVA) was proposed as a toughening agent to incorporate with furfuryl alcohol (FA) to form FA/PVA precursor and impregnate wood in a one-step method. After in situ polymerization upon heating, a hydrophobic network composed of polyfurfuryl alcohol (PFA) and PVA was formed within the wood scaffold. The impact toughness, as well as some water-related properties of modified wood including the contact angle, water absorption, moisture adsorption, and dimensional stability were investigated in this study. The results showed that the impact toughness of wood significantly decreased after furfurylation. The incorporation of PVA could alleviate the reduction, and this effect was more obvious for highly furfurylated wood. PVA could penetrate and bulk the wood cell wall to a certain degree, but increased concentration of PVA may negatively influence the penetration of FA in wood cell wall. PVA showed only slight influence on water-related properties of FA modified wood, and it depended on both concentrations of PVA and FA. All results indicate that incorporation of PVA in FA system is a promising approach to enhance the toughness of FA modified wood.

Two new phenolic rhamnosides ( 1 – 2 ) and 12 known phenolic compounds ( 3 – 14 ) were isolated from the ethanolic extract of Cinnamomum camphora barks by repeated column chromatography. The structures of all isolated compounds were identified by comprehensive spectroscopic data analysis such as high-resolution electrospray ionization mass spectra, nuclear magnetic resonance, optical rotatory dispersion and chemical method. In vitro assay revealed that compound 8 showed strong inhibitory activity against tyrosinase, and compounds 1 ,  3–7 ,  8–9 , 13 showed obvious acetylcholinesterase inhibitory activity.