Research Articles

The effects of a three-layer structure and age on the mechanical properties of moso bamboo were investigated. The ages of 1-, 3-, and 5-year-old bamboo were chosen to make test samples, and specimens from each age of moso bamboo were divided into three groups (raw bamboo, bamboo removed from outer layer, and bamboo removed from inner layer) for evaluation of modulus of rupture and parallel-to-grain compressive strength. The regression analysis was completed to evaluate the relationship between mechanical properties and bamboo age. The results showed that the age of moso bamboo was positively correlated with the flexural and parallel-to-grain compressive strengths. The mechanical strength of moso bamboo increased with the increased age of moso bamboo. For the moso bamboo with same age, the flexural and parallel-to-grain compressive strengths decreased for the samples without bamboo outer layer. However, for the samples without bamboo inner layer, the parallel-to-grain compressive strength remained unchanged, but the flexural strength increased. The outer layer of bamboo with high toughness and flexibility played an important role during bending. However, the inner layer of bamboo is relatively brittle, which has negative effects on its flexural strength. These results provide an important basis for the bamboo used in engineering.

By structurally and practically analyzing the use of Nd: YAG laser for cutting black walnut veneer, this study considered practical and environmental concerns regarding the global warming protection measures. A numerical model of laser wood veneer cutting was based on the relation between process parameters and the material thickness. A pulsed Nd: YAG was used to cut black walnut veneer of 0.3 mm thickness under different machining conditions regarding laser power and cutting speed to study the cut kerf width. An analysis of variance was conducted to test the significance of machining parameters. The parameters studied were laser power, cutting speed, kerf width, cut surface, safety, and eco-friendliness. The results showed that the kerf width decreased significantly with increased cut speed and, inversely, by laser output power. An efficient cut with a narrow kerf, clean and smooth, with less burn, was possible at laser cutting speeds of 2.5, 5.0, and 5.5 mm/s with kerf widths of 0.544, 0.69, 0.62 mm, respectively. As multiple factors affect the micro-thin wood laser cutting process, finding the optimal process parameters is crucial for successful machining with no burn effect.

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.