Research Articles

The complexation conditions and complex characteristics of 1,2,3,4,6-O-galloyl-β-D-glucose (PGG), a typical hydrolyzable tannin, and Ge4+ were studied. Species of the PGG-Al3+ complex formed in various water-methanol systems (20% to 100%, v/v) were investigated. The results showed that the amount of PGG and Ge in the precipitate was substantially influenced by the initial Ge/PGG molar ratio. The highest amount of the precipitate was obtained at the initial Ge/PGG molar ratio of 1:2 and the stoichiometric ratio (Ge/PGG molar ratio) of the precipitates gradually decreased from 0.72 to 0.30 concomitant to a decrease in the initial Ge/PGG molar ratio from 1:1 to 1:4. Precipitation experiments of Ge4+ by four hydrolyzable tannins from Chinese gallnut (TA), chestnut shell (CT), Platycarya strobilacea infructescence (PT), and Valonia (VT) were compared. The results indicated that the amount of the precipitate was substantially influenced by the initial tannin/Ge ratio and pH and was slightly influenced by the reaction time. The highest amount of the precipitate was obtained at the initial tannin/Ge mass ratio of 2.3:1 and pH 7.2. Stability of the TA-Ge, CT-Ge, VT-Ge, and PT-Ge precipitates in several solutions was determined. The TA-Ge precipitates showed relatively high stability in the test solvents compared to that of other tannins.

The effect of nanographene amount was evaluated relative to the physical, mechanical, thermal, and morphological features of wood-plastic composites. Composites were prepared using recycled polyethylene (high-density polyethylene), nanographene, and wood-flour. The amount of 80% of polymer matrix and 20% of wood flour, and nanographene at four weight levels of 0.5%, 1.5%, and 2.5%, were used. An internal mixture was utilized for making the samples. The results showed that with the 0.5 wt% increase of the amount of nanographene, the tensile and flexural strengths, the flexural and tensile modulus and the notched impact strength composite increased. With the addition of 2.5 wt% nanographene, these properties decreased. With the increase of the level of nanographene by 2.5 wt%, water absorption and the thickness swelling of the composite decreased. With the increase of the level of nanographene, the level of residue ash and thermal stability also increased. Scanning electron microscope images showed that the samples with 0.5 wt% nanographene had less holes and a smoother surface compared to the other samples.

Excessive inhalation of airborne wood dust has a negative impact on employees’ health and is a common issue. There are available hazard control methods to protect workers from exposure to airborne wood dust. These methods include ventilation of the workplace and the use of personal protective equipment against dust. In this study, micro-scale furniture manufacturing enterprises were investigated because the sector and the scale of the enterprise are among the factors affecting the exposure to dust. A structured questionnaire was conducted by face-to-face interview method in this study. In addition, workplaces and working conditions of 53 enterprises were observed during on-site visits to conduct the questionnaires. The relationship between categorical variables was investigated using the Chi-square test. Among the interviewed employees, 9.4% were not concerned about the harmful impact of solid wood dust on health. The least used ventilation method was local exhaust ventilation, and at any interviewed site the occupational exposure limit value to dust was unknown. Medium density fibreboard was the most preferred raw material. Because wood dust was generally underestimated as an occupational health risk factor, this study concludes that ventilation applications that reduce exposure to dust were also insufficient.

In technical applications of wood-based composites, the predictability of elasticity and strength is important. The aim of this study was to predict the static modulus of elasticity and tensile strength of thin (0.55 mm ± 0.05 mm) birch veneers. Based on the dynamic modulus of elasticity estimated via means of wave transmission time the observed dynamic modulus of elasticity was on average 14% lower than the corresponding static modulus of elasticity. This difference could be explained by a decreased measuring area during the tensile testing or by defects within the samples. The dynamic modulus of elasticity correlated well with the static modulus of elasticity (r = 0.821). Therefore, using wave transmission time to non-destructively predict the elasticity of veneers proves to be a promising tool. The dynamic modulus of elasticity showed a significant and positive correlation with the tensile strength (r = 0.665), but this correlation was weaker than with the static modulus of elasticity. Therefore, the wave transmission time or the static modulus of elasticity must be combined with additional strength-influencing properties, such as fiber angle or density, to allow for a highly accurate prediction of tensile strength.

The drainage- and dewatering-controlling mechanisms in a screw press were detailed in this work. Three pulps (kraft pulp, bleached chemi-thermomechanical pulp, and thermomechanical pulp) were studied to compare a wide range of wood fibre types. The dewatering was controlled by the screw press parameters and the pulps’ properties. Filtration was found to be the controlling mechanism in the first part of the screw press for the three pulps, and it was less important when the fines content was greater. In the compression zone, the degree of compression was affected by the pulp flexibility and the fibres’ tendency to entangle. Filtrate flow rate monitoring along the screw press could be a good indicator of where the transition from filtration to consolidation occurs. The pressure along the screw press did not change much in the filtration zone, and it notably increased near the discharge end. When the drainage was very high, the pulp feed increased, causing the pulp axial velocity in the end part to be greater than the screw’s linear advance.

The use of natural fiber polymer composites is being considered in many applications. In the current work, the three-body abrasion performance of an alkali-treated eucalyptus and polyvinyl chloride (PVC) composite was studied at different applied loads (40 to 130 N), sliding velocities (1.86 to 3.73 m/s), sliding distance (up to 4.0 km), and abrasive particle size (0.25 to 0.75 mm). The results showed that the applied load and sliding distance affected three-body abrasion. At lower applied loads and shorter sliding distances, higher specific wear rates (Ws) and more obvious worn surface features were exhibited, while sliding velocity had less of an effect on the wear behavior. The Ws and worn surface roughness increased as abrasive particle size increases, and deeper grooves and higher deformation on the worn surface were found due to the enhanced material loss from the larger particle size abrasive.

In the first part of this study, the Kelly repertory grid technique was used to determine the most preferred attributes of overlay materials used in wood-based panel furniture in Malaysia. This was followed by a questionnaire survey of 20 large wood-based panel furniture manufacturers to establish the trends in the use of overlay materials and the success factors of their utilization. The results showed that natural wood veneer was the most preferred overlay material, and the common local veneer species used included kembang semangkok, rubberwood, and bintangor. Meanwhile, the predominant imported veneer species were white oak, white ash, and walnut. The factor analysis showed that the properties of the overlay materials and market preferences were the driving factors for their successful utilization. The results clearly showed that natural wood veneer was preferred due to its wood-like, natural, and living attributes, and customers were prepared to pay a price premium for furniture with wood veneers compared to the other types of overlay materials.

The objective of this investigation was to elucidate the structural changes of the polysaccharides isolated by hydrothermal treatment of corn bran after twin-screw extrusion. The structures and antioxidant activities of the purified polysaccharides were investigated and compared by monosaccharide analysis, Fourier transform infrared (FT-IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR). The results showed that the structures of the linkages and monosaccharide components of the purified polysaccharides were not affected strongly by the twin-screw extrusion pretreatment. However, the purified polysaccharides isolated from pretreated samples displayed significant differences in monosaccharide ratios, degree of branching/ linearity, and molecular weight. These physical changes may be related to the decrease of antioxidant activities of the polysaccharides. The present investigation contributes to the knowledge of how pretreatment by twin-screw extrusion affects the chemistry of corn bran polysaccharides. Results can be applied to improve the efficiency of hydrothermal extraction of polysaccharides from corn bran.

Selective Laser Sintering (SLS) technology can be utilized to recycle residues from forestry and agriculture, thereby alleviating shortages of materials and reducing energy consumption by producing wood-plastic pieces for industrial application. The mechanical strength of wood-plastic SLS parts is low, which restricts the application of this technology. In this study, a novel type of sisal fiber/poly-(ether sulfone) (PES) composite was prepared using a polymer mixing method in order to improve the mechanical properties of SLS parts. Single-layer sintering method was adopted to determine the proper processing parameters. The mechanical properties of the parts with different ingredient ratios and different particle sizes of sisal fiber before and after post-processing were tested using a universal testing machine. The morphology was examined using scanning electron microscopy (SEM). Results showed that the mechanical properties of the printed parts were relatively enhanced; when the mixing ratio of composite powder was 10/90 wt/wt. In addition, the part fabricated by powder of particles size less than 0.105 mm (0.125 mm ≥ PS < 0.105mm) had the best mechanical strength. Moreover, the post-wax treatment significantly improved the strength of the parts, and the surfaces became smoother.

Saccharomyces cerevisiae is one of the most promising unicellular fungi on account of its vital applications in biotechnology as well as bioethanol production. Improvement of ethanol production via very high-gravity (VHG) fermentation (fermentation at high sugar levels) was successfully developed using the ethidium bromide (EtB) mutagenesis of S. cerevisiae. This study found two developed mutants of S. cerevisiae (EtB20a and EtB20b) with varied capacity for ethanol production using EtB, depending on random amplified polymorphic DNA analysis. Mutant EtB20b showed improved ethanol yield (19.5%) compared with the wild-type (18.0%), while the other mutant EtB20a exhibited retarded ethanol production (9.1%). Optimization of ethanol production by mutant EtB20b was performed under other conditions including temperature, pH, inoculum size, and incubation period. The highest production capacity of the yeasts was 20.8, 19.9, 19.5, and 19.5% at an optimum temperature of 30 °C, pH 6.0, incubation period of 72 h, and 1 mL of yeast suspension (optical density at 600 nm) with glucose utilization of 42.6, 40.7, 39.8, and 39.9%, respectively.