Research Articles

The appropriate diameter ratio of log top and butt ends when using a round bar (cylinder shape) as a log model for estimating the density and Young’s modulus of a log was investigated. Square timbers of Japanese cedar (Cryptomeria japonica D. Don) with a length of 1200 mm were used as specimens and were machined into circular truncated cones. A longitudinal vibration test was performed to obtain the Young’s moduli of the square timbers and the circular truncated cones. The Young’s moduli were calculated using the circular truncated cone model and the round bar model. The density and Young’s modulus calculated by the circular truncated cone model were similar to those of the square timbers. Hence, it is considered that the circular truncated cone was effective for estimating the densities and Young’s moduli of logs. The density and Young’s modulus calculated by the round bar model differed from those of the square timbers when the diameters of the top ends were small. However, it is considered that the round bar can be used as a log model for actual logs.

Several potential approaches were evaluated to improve the physical and mechanical properties of 3 mm HDF panels used as door-skins. Six different composition recipes were applied by varying the ratio of hardwood-to-softwood fibers and the addition of bark. The density, surface absorption, bending strength, modulus of elasticity, and internal bond of the HDF panels manufactured on an industrial line were determined. The best performance was obtained for the recipe with 20% hardwood fibers, 80% softwood fibers, and less than 5% bark. The influence of spraying the fiber mattress before pressing, by means of water and two different release agents, was also tested. The obtained results are applicable at any HDF producer and can be used for process optimization.

Cellulose nanofibrils (CNFs) were oxidized by the TEMPO oxidation system from bleached kraft eucalyptus pulp, and layered double hydroxides (LDHs) were prepared via the hydrothermal method. MgAl-CO₃-LDHs/CNFs composite films with different LDH ratios were prepared via a filtering/evaporation technique that endowed the nanocomposites with barrier and strengthening properties. The MgAl-CO₃-LDHs could uniformly disperse in the CNFs matrix with an improved reciprocal adhesion, and the surface result was smooth and continuous. The basic structure of the membrane did not change, but the thermodynamic properties and the water vapor barrier property improved. This composite membrane can be widely used in food, pharmaceutical, and chemical packaging industries as a gas-liquid barrier material.

Chlorine dioxide bleaching is an important component of elemental chlorine-free bleaching. A method is introduced in this work to optimize process conditions for chlorine dioxide delignification based on nonlinear programming and response surface analysis. An energy consumption model for chlorine dioxide bleaching is established, as well as statistical models for the brightness, viscosity, and absorbable organic halogen content with the process conditions. The results from the model predict that the cost can be reduced compared to the optimization results of the response surface analysis and experiments.

Tungsten trioxide (WO₃), which is a semiconductor, was hydrothermally synthesized onto the surface of wood. After the in-situ synthesis of WO₃ nanoparticles on the wood surface, the wood exhibited photochromic and superhydrophobic properties. The WO₃ nanostructures were fabricated on wood surface through a two-step hydrothermal process at 90 °C or 120 °C for 6 h. Chemical composition, crystalline structures, and morphologies of the WO₃-coated wood were characterized. The results indicated that the amount of WO₃ nanostructures on the surface of the wood substrate was 12.89 wt.%. Meanwhile, the WO₃ nanostructures were composed of fine nanoparticles and highly crystallized by SEM and XRD analysis. When the sample was irradiated under ultraviolet (UV) light (365 nm), there was an obvious color change after 10 min (ΔE). The water contact angle measurements demonstrated that the fluorosilane modified WO₃-coated wood surfaces possessed a superhydrophobic behavior with a contact angle of 152°. The sliding angle was less than 10°. Photochromic and superhydrophobic properties were achieved by a facile process, which could contribute to the development of functional wood with an aesthetic coloring.

APMP (alkaline peroxide mechanical pulp) of bamboo was treated in NaOH-urea aqueous solution to modify the fiber properties. The effects of soaking time, fiber concentration, alkali dosage, freezing temperature, and freezing time were evaluated by single-factor experiments. The optimal conditions were determined as a soaking time of 10 min, a fiber concentration of 15%, an alkali dosage of 6%, a freezing temperature of -7 °C, and a freezing time of 40 min. Compared with the properties of untreated APMP, the tensile index of the treated APMP was increased by 64%, and the burst index was increased by 82%. The bulk was reduced by 15%, and the softness was increased by 18%. There was no obvious variation on the folding strength. According to the instrumental analysis, there were no significant effects on the structure in terms of functional groups, the crystalline region, or the fiber surface morphology; however, the variation on the fiber quality was more significant.

White poplar is an important biomass resource because of its high yield and fast-growing characteristics. Experiments were conducted to study the effects of microwave power, moisture content, and particle size on the heating rate and biochar yield. A Central Composite Design (CCD) was used to optimize the biochar yield. The CCD results showed that a maximum temperature-increasing rate of 2.71 °C/s was obtained with a microwave power of 2 kW and a small particle size of 100-mesh. High power, small size, and high moisture content would benefit the increase of the heating rate. An optimum biochar yield of 0.905 kg per kg poplar was obtained with a microwave power of 3 kW, moisture content of 1%, and temperature of 500 °C.

Four fiber fractions from poplar alkaline peroxide mechanical pulping, performed with refiner-chemical preconditioning (P-RC APMP), were used to estimate inter-fiber bonding capacity. The relationship between fiber characteristics and inter-fiber bonding capacities was investigated. The surface lignin content of the long fiber fraction was slightly lower than that of the short fiber fraction. Atomic force microscopy (AFM) images showed that the fiber surfaces were heterogeneous (i.e., different cell wall layers were exposed along the fiber surface). The fiber fractions that had lower surface lignin content had higher bonding capacities. Furthermore, modified PFI beating was used to peel the surface of the fibers. After the peeling treatment, the fiber surface charge increased remarkably, while the surface lignin concentration decreased considerably. The lignin and charge on the fiber surface are the two key factors for estimating the inter-fiber bonding capacities.

The primary and secondary amines of tetraethylenepentamine (TEPA) were N-methylated into tertiary amines through the Eschweiler-Clarke reaction. A straw-based tertiary amine-supported material (STA) was developed for SO2 removal, using a wet impregnation process. The effect of the adsorption conditions, such as the moisture content, flow rate, and adsorption temperature, as well as the regeneration performances were studied. Experimental results showed that STA has high SO2 adsorption capacity (approximately 100 mg/g) and can be regenerated at 100 °C. Furthermore, the adsorption of SO2 molecules on tertiary amine was studied using density functional theory (DFT). The most stable geometries of the adsorption structure in five possible positions, the geometric changes after the adsorption, and the corresponding adsorption energies were analyzed. The results showed that modified TEPA (M-TEPA) has four potential adsorbed sites (N(1,3,4,5)) with a small adsorption energy, indicating that the adsorption is weak. Moreover, the energy of the adsorbed SO2 on the N(1,3,4,5) is less than zero, indicating that the adsorption process is exothermic and spontaneous. The theoretical investigation agreed well with the experimental results.

Sequential submerged cultivation with different induction media as inducers of ligninolytic enzyme production by Pleurotus ostreatus strains was assessed by measuring laccase activities. An unconventional material, alkali lignin, was used for the first time as an inducer for different strains to enhance laccase activity. The P. ostreatus strains secreted similar but relatively high levels of laccase activity when the induction media contained alkali lignin with or without glucose. The laccase enzyme of different P. ostreatus strains in the different media exhibited large differences, and the wild strain YAASM 0568 exhibited enhanced production of laccase compared to other cultivated strains. The laccase activities of wild strain YAASM 0568 were nearly 3.4-, 3.3-, and 5.4-fold higher than that for cultivated strains CCMSSC 00322, CCMSSC 00406, and CCMSSC 00336, respectively, when the induction media contained alkali lignin, inorganic salt, and vitamin B1. In general, induction media containing alkali lignin with or without glucose were favorable for laccase secretion. The results revealed that the type of induction material and the nature of the fungus play important roles in the expression of ligninolytic enzymes. These findings would be helpful for selection of the appropriate type of strain and for optimization of integrated industrial ligninolytic enzyme production.