Volume 16 Issue 2

This work presents a study on the preparation of recycled wood fibre using different types of grinding equipment. It is also concerned with fibre preparation in an aerodynamic environment and describes the possibilities of using the material in various finished products. The authors used bio-rejects from the production of composite board materials, e.g. fibreboard and medium density fibreboard (MDF), in the form of lump scraps, as research material. In order to evaluate the efficiency of woodfibre waste recycling using various grinding equipment, the authors analysed the qualitative characteristics of the resulting semi-finished woodfibre materials and mathematically calculated the primary technological and design parameters of the grinders. The results of the study provide a scientific basis for the efficiency of a fundamentally new recycled wood fibre dry preparation method and system.

The physical and mechanical properties are key indexes for determining the quality of particleboards. For this reason, a study on evaluating the physical and mechanical properties of particleboard via a new method has considerable value. Thus, a method based on principal component regression (PCR) analysis and random forest (RF) is proposed in this paper. First, the problems requiring resolution are described after analyzing the production process parameters as well as the physical and mechanical properties of particleboard. Then, an analysis and prediction models based on the PCR and RF method is established. On the basis of the PCR method, the key process parameters that affect various physical and mechanical properties are determined. Based on the RF method, the analysis and prediction model are built from the previously determined process parameters of the physical and mechanical properties. Finally, through experimental analysis, the effectiveness of the analysis and prediction models based on the PCR and RF method are verified. This work was able to determine the relationship between the process parameters and the physical and mechanical properties, which can help improve practical industrial manufacturing effectivity.

Oil was produced from sugarcane leaves hydrolysate (SLH) in the newly isolated oleaginous yeast Cyberlindnera subsufficiens NG8.2, using a two-stage cultivation method. The SLH contained sugars derived from both the dilute acid pretreatment of leaves and subsequent enzymatic hydrolysis (16.6 g/L of glucose and 15.87 g/L of xylose). The Cyberlindnera subsufficiens NG8.2 produced oil containing 18.73 wt% of palmitoleic acid, with a 0.99-g/L oil yield when grown in the SLH. Removal of phosphate from the SLH by Ca(OH)2 treatment (SLH-P) resulted in an increased oil yield of 1.38 g/L, but the palmitoleic acid content of the oil decreased to 12.45 wt%. Supplementation of the SLH-P with 3.12 mM of Mg2+ increased the palmitoleic acid content in the oil to 15.80 wt% and the oil yield to 1.58 g/L, with a palmitoleic acid yield of 2.09 mg/g sugarcane leaves. Thus, sugarcane leaves are a promising feedstock for palmitoleic acid production using Cyberlindnera subsufficiens NG8.2.

Transparent wood (TW), a new type of composite material with good optical transmittance and excellent mechanical properties, has attracted great interest in recent years. In this study, a hydrogen peroxide strategy was used on rubber wood (Hevea brasiliensis Muell. Arg) to eliminate lignin and hemicellulose. Subsequently, delignified wood was combined with each of three impregnants of refractive index similar to that of cellulose to obtain transparent wood (TW). Impregnation with polyvinyl-pyrrolidone (PVP), polyvinyl alcohol (PVOH), and methyl methacrylate (MMA)) resulted in transparent woods, which were named PVP-DRW, PVOH-DRW, and PMMA-DRW, respectively. The micromorphologies, chemical compositions, thermal stabilities, chemical functional groups, optical transmittance, and mechanical properties of the raw RW and of each processed sample were characterized. The results showed that the optical transmittance of PVOH-DRW (76.6%, λ = 600 nm, d=0.70 mm) was similar to that of PVP-DRW (73.4%, λ = 600 nm, d = 0.74 mm) and higher than that of PMMA-DRW (64.6%, λ = 600 nm, d = 0.73 mm), but PMMA-DRW had a higher mechanical strength (fracture strength of 230.14 MPa). Therefore, the preparation of transparent wood with RW as the substrate is expected to be a potential material candidate for high-strength composites.

This study investigated the synergistic effect of temperature and ultrasonic field on seawater modification of wheat straw fibers via orthogonal design. Based on orthogonal results, physicochemical and thermal properties of wheat straw fibers were also reported. The results indicated that a 120 min seawater modification of the fibers at a 70 °C heating temperature and 90 W ultrasonic power increased water absorption. The increase was attributable to the removal of the waxy layer and non-cellulosic materials, which, in turn, decreased the silicon elemental content and hydrogen bonding, as well as increased surface roughness, crystallinity, and thermal stability. The physicochemical and thermal characterization showed that this modification method has potential to be a viable industrial application.

Microwave (MW) pretreatment was used to increase the impregnability of Oriental spruce sapwood (Picea orientalis (L.) Link.). Wood samples with moisture contents of 55% and 83% were subjected to different MW energy treatments (1156 MJ/m3 and 1542 MJ/m3). Additionally, the mechanical properties of the treated wood samples were tested to determine the degradation caused by exposure to the MW radiation. According to the test results, the average preservative material retention rates increased by 47.5% and 70% for the samples with initial moisture contents of 55% and 83%, respectively, compared to the reference samples. The mechanical properties of the MW pretreated wood samples decreased within the range of 1.7% to 2.9% in the case of the compression strength; changed within the range of (+)1.9% to (-)6.1% in case of the bending strength; and changed within the range of (+)0.9% to (-)6.2% in case of the modulus of elasticity (MOE). The application of MW energy at different power settings on the samples with similar moisture levels was determined to have no impact on the mechanical properties of treated wood.

An alkali-mediated hydrothermal approach was optimized for partial extraction of high-purity hemicellulose (xylan) from a timber waste product (unbleached eucalyptus sawdust). The extraction process was: a) extractives removal using sequential solvent extraction; b) alkali-mediated hydrothermal extraction of hemicellulose; and c) purification of the isolated hemicellulose fraction. Biomass was extracted in an autoclave at a fixed temperature of 121 °C while varying the extraction time (1 h to 2.5 h) and alkali concentration (10%, 15%, and 20% w/v). Using this simple approach, high purity polymeric hemicellulose with molecular mass (21 to 30 kDa) was recovered in yields of 35 to 37%. The isolated hemicellulose can be chemically transformed into high-value commercial products such as prebiotics (xylooligosaccharides), surfactants, hydrogels, and food packaging materials. The purified residue can be utilized in existing kraft pulping processes. The integration of hemicellulose extraction into existing pulping process represents additional valorization of timber resources.

Tannins and their toxic effects against various decay organisms have been interrelated for centuries. As natural products have gained more interest, waste from several production fields abundant in tannins has yielded promising components for wood preservation. In this work, the main approach was to split condensed tannins into smaller fractions by chemical hydrolysis and evaluate their suitability for beech wood impregnation. Commercial extract from black wattle was treated with mineral acid of low concentration. The volatile hydrochloric acid was completely removed after reaction by evaporation in the course of freeze-drying. The modified extract was then applied as aqueous solution into beech wood. The water resistance of the modified beech wood was not increased significantly, and scanning electron microscopy (SEM) showed no evidence of tannin successful bonding within wood cells. Nevertheless, after strong leaching cycles, part of the extract accumulated in fibers. Moreover, lyophilization was found to be a suitable technique to eliminate volatile acids from temperature-sensitive extracts, such as tannins. These findings could help in the development of water-borne tannin formulations for wood protection, while using phlobaphene formation as a potential natural pathway of tannin autocondensation.

Wood is a material commonly found in nature and is widely used in all professions and industries. Because wood has varied growth cycles and physical properties, there are large differences in its usage and commercial price. In addition, some woods are nationally protected species. Therefore, it is of great importance to accurately identify the type of wood. Traditional wood recognition methods rely on experts and specialized equipment. To facilitate wood recognition, this paper proposes an approach for wood recognition using images. Next, a transfer learning technology was used to extract the textural features of wood, and a global average pooling (GAP) layer was used to reduce the number of features. Finally, the extreme learning machine (ELM) was used for classification. The recognition accuracy of this approach for the Wood Species Dataset was 93.07%, which was higher than the method used by the data provider. This approach had a higher recognition accuracy and a more stable recognition performance than previous approaches.

The degradation of wood changes various properties; these changes can favor its usage in particular instances, e.g., as an insulation material. Knowledge of the moisture content and movement of moisture in building materials is crucial. The primary focus of this paper is the diffusion coefficient and equilibrium moisture content of three wood species after degradation via Trametes versicolor. Values for the diffusion coefficients were determined under different conditions: a temperature of 20 °C ± 2 °C; and 3 relative air-humidity settings, i.e., 30% ± 3%, 60% ± 3%, and 96% ± 3%. The differences in the longitudinal and transversal directions were statistically significant for all conditions, while the differences in the diffusion coefficients were non-significant for the first two relative-air-humidity settings. A portion of the diffusion coefficient calculation data was used to develop a sorption isotherm for all wood species. The equilibrium moisture content of the degraded wood was determined for each condition. Duncan’s multiple-range test showed that the wood species was a significant factor; therefore, the isotherm had to be plotted for each wood species. The number of sorption sites in the monolayer in degraded spruce wood was different from the number in degraded beech and oak wood.