Volume 71, Issue 3

Cinnamomum micranthum (Hayata) Hayata is a tree species that is often confused with Cinnamomum kanehirae Hayata, which is an endemic species in Taiwan and the sole natural host of the valuable medicinal fungus Antrodia cinnamomea. However, the two species are highly similar in morphology and difficult to distinguish based on traditional vegetative structures or wood anatomical methods. The aim of the present study was to identify of these two species by DNA and chemical analysis. The complete chloroplast genome of C. micranthum has been determined and compared with that of C. kanehirae . The leaf methanol extracts of these species were also analyzed by ultra-performance liquid chromatography (UPLC). The length of the C. micranthum chloroplast genome was 152675 bp, i.e. 25 bp shorter than that of C. kanehirae . In phylogenetic analysis, C. micranthum was more closely related to C. kanehirae than other six Lauracea species. Six validated insertion/deletions of bases in the DNA (InDels) are suitable for differentiation of the two species. Moreover, high amounts of linalool and sesamin were present in the leaves of C. kanehirae , but not in C. micranthum . Overall, this study provided new insight for distinguishing the two species on the basis of the chemical composition of the leaves and the InDel markers.

Isolation and analysis of lignin and lignin-carbohydrate complexes (LCCs) were performed to understand the better delignification ability of prehydrolysed wood chips. Lignin analysis showed that prehydrolysis led to a slight depolymerisation and an increase in free phenolic group content. The yield measurement and composition analysis of LCCs of mixed softwoods (SWs) and mixed hardwoods (HWs) revealed essential differences. In the case of SW, the amounts of lignin and xylan involved in LCCs were significantly lowered, whereas in the case of HW, less cellulose, glucomannans, and xylans were detectable in the residual LCCs. The molecular mass distributions of glucomannan-lignin and xylan-lignin fractions were not changed significantly.

Heat treatment (HT) enhances various properties of wood (W), but it takes a relatively long time and W HT is a source of fire hazard. To improve the properties of W HT , Populus beijingensis W. Y. Hsu wood was impregnated with nitrogen-phosphorus (NP) fire retardant (10% aqueous solution) and the effects of the combined NP treatment and HT were observed. Control groups included native wood and samples from W HT200°C, 120 min and W HT220°C, 120 min . The surface color, dimensional stability, and combustion properties of the treated samples were examined. NP pre-treatment intensified the effectivity of HT 150°C , where the treatment time decreased by 75%. The decomposition and catalytic dehydration of NP treatment enhanced the dimensional stability and darkened the wood surface. After HT, the NP fire retardant was transformed from dispersive particles into a uniform layer on the inner surfaces of wood. The heat release rate (HRR) decreased by 60.3% and the residual mass (RM) increased by 61.1% in W NP, HT compared to normal W HT200°C poplar.

In continuation of the previous study concerning the effects of a combined treatment of wood with nitrogen-phosphorus (NP) fire retardant and heat treatment (HT), the hygroscopicity, leachability, thermal stability, Fourier transform-infrared (FT-IR) spectra, and X-ray diffraction (XRD) properties of Populus beijingensis W.Y. Hsu have been investigated. The wood samples were impregnated with 10% NP fire retardant solution and exposed to HTs at 140°C–160°C for 30 min. HT of NP treated wood reduced the moisture absorption and enhanced the leaching resistance of NP and improved the thermal stability. The HT decomposes the NP and the acidity of these degradation products has a dehydration effect on the wood polysaccharides, and the number of hydroxyl groups in wood decreased substantially. The crystallinity index of the NP-impregnated and heat-treated wood also increased. The post low-temperature HT enhanced the fixation of the NP fire retardant and hydrophobicity of the NP-treated wood.

Poly(vinyl) alcohol (PVA)/nanosilica (SiO 2 ) based electrospun nanofibers has been deposited on wood substrate by means of the roll electrospinning process. The nanofibrous coating was hydrophobized by self-assembled monolayers of octadecyltrichlorosilane (OTS) via a sol-gel dipping process. The PVA/SiO 2 nanofiber coating and OTS hydrophobized coating were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDXA). All methods confirmed the formation of OTS monolayers on hybrid coatings. The adhesive strength and resistance to scratch of nanofibers coating was also evaluated.

Wood-SiO 2 composites (WSiO 2 Cs) were prepared by means of the sol-gel process with methyltrimethoxysilane (MTMOS) as a reagent, and the physical properties, structure and thermal decomposition kinetics of the composites has been evaluated. The dimensional stability of the WSiO 2 Cs was better than that of unmodified wood, especially in terms of the weight percent gain (WPG), which achieved values up to 30%. The 29 Si-NMR spectra show two different siloxane peaks (T 2 and T 3 ), which supports the theory about the formation of MTMOS network structures. Thermal decomposition experiments were also carried out in a TG analyzer under a nitrogen atmosphere. The apparent activation energy was determined according to the iso-conversional methods of Friedman, Flynn-Wall-Ozawa, modified Coats-Redfern, and Starink. The apparent activation energy between 10 and 70% conversion is 147–172, 170–291, 189–251, and 192–248 kJ mol −1 for wood and WSiO 2 Cs with WPGs of 10, 20, and 30%, respectively. However, the reaction order between 10 and 70% conversion calculated by the Avrami theory was 0.50–0.56, 0.35–0.45, 0.33–0.44, and 0.28–0.48. These results indicate that the dimensional and thermal stability of the wood could be effectively enhanced by MTMOS treatment.

In contact with soil, copper (Cu) formulations as preservatives are expected to inhibit wood decay by fungi and other soil-borne microorganisms. However, Cu-resistant brown-rot (BR) fungi lead to premature failures of utility poles at some sites. In this study, the service lives of 111 utility poles of Norway spruce ( Picea abies (L.) H. Karst) (73 from Switzerland and 38 from Germany) impregnated with Cu-based wood preservatives were investigated. Three segments of each utility pole were analyzed. The severity of decay was dependent on the preservative formulation. BR fungi and in particular Antrodia species were predominantly isolated from utility poles that were not treated with a co-biocide, e.g. boron (B). Cu-sensitivity of several isolated BR fungi was confirmed in studies on Cu-amended medium and in Cu-treated wood. Isolates of Fibroporia vaillantii and Serpula himantioides showed a higher Cu-tolerance than the highly Cu-tolerant Empa isolate Rhodonia placenta (Empa 45) or Antrodia serialis .

Boric acid (BA) effectively controls wood-rotting fungi and termite attack but is readily leached out in outdoor exposure. A newly developed tannin-boron (TB) complex has been investigated to reduce BA leaching and to preserve beech plywood from biological attack. Wood veneers were impregnated with different TB solutions and then bonded with a melamine urea formaldehyde (MUF) adhesive for bond class 2 applications. The formation of a solid hydrophobic TB network on the veneer surfaces partially decreased the tensile shear strength of plywood but the prepared panels met the requirements for bond class 2. The plywood samples made from veneers treated with only BA solutions showed fair resistance against white rot fungus and termite attack, but the durability decreased even after mild leaching tests. The panels made of treated veneers with TB formulations showed instead a high resistance against biological attack after mild leaching and to some extent after severe leaching tests. This depended on the concentration of tannin and BA in the solutions. Favorable results were obtained with 20% tannin in the formulation. The results of the termites feeding choice test were more positive than those obtained by a forced feeding test. The control samples were attacked faster and showed higher weight loss when alternative samples included TB formulations.

A bacterial mixture of Pseudomonas putida and Pseudomonas fluorescens has recently shown the potential to completely reduce monoterpenes within pine wood particles on a laboratory scale. This bacterial combination was then applied onto pine wood strands to obtain emission-reduced oriented strand boards (OSB) produced on a technical scale. Laboratory tests with bacterial inoculated strands were carried out to optimise parameters such as aeration and incubation time. Residual terpene emissions were measured by solid-phase microextraction/ gas chromatography-mass spectrometry (SPME/GC-MS) analysis. Daily aeration, specific pre-cultivation, and increased inoculum size eventually resulted in a reduction of the major softwood terpenes α-pinene, β-pinene, and Δ3-carene by 60, 70, and 40%, respectively, after only 2 days of incubation. Based on these results, OSB were manufactured from strands after bacterial pre-treatment for 2 or 4 days. As expected, terpene emissions from OSB decreased with increasing incubation time. However, even after only 2 days of incubation, α-pinene and β-pinene emissions were appreciably reduced by 40 and 70%, respectively. The method developed here thus appears to be feasible for industrial application although a further reduction of pre-treatment time would be advantageous. The inoculation step will also have to be adapted for technical implementation into the OSB production process.

Light layer honeycomb panels could replace traditional wood materials, if their stiffness and strength properties could be improved. The aim of this research was to design and determine elastic properties of sandwich panels (SPs) based on a dual corrugated HDF core. Stiffness matrix values of elements were determined by a numerical method. The 3D calculation results were compared with those of the homogeneous model. The calculation results were collated with those of experimental investigations. It was demonstrated that the linear elasticity modulus as well as the modulus of rupture of the SPs were comparable with mechanical properties of a particle board with identical thickness, while the SP has a 1/3 lower density. The panel core exhibited significant orthotropic properties. In the xy plane it could be characterized as an auxetic structure. The homogeneous model leads to results similar to those achieved from the 3D model and observed in experimental tests.