Volume 15 Issue 1

Cellulose nanocrystals (CNC) were successfully isolated from oil palm empty fruit bunch (EFB) using sulphuric acid hydrolysis preceded by alkaline deep eutectic solvent (DES) pretreatment and bleaching. In this study, an alkaline DES consisting of potassium carbonate and glycerol (molar ratio of 1:7) was used as the pretreatment solvent to promote the dissolution of lignin and hemicellulose. The processing parameters of acid hydrolysis were optimized using Box-Behnken Design. The results showed that the yield of CNC was 37.1%, under the optimal conditions of 60.0 wt% acid concentration at 46.1 °C for 58.5 min. The field emission scanning electron microscopy (FESEM), chemical composition analysis, and Fourier transform infrared (FTIR) results indicated that unwanted impurities, such as hemicellulose and lignin, were efficiently eliminated from the raw EFB fibers by DES pretreatment and bleaching. The average diameter of CNC was less than 10 nm. The raw EFB fiber, treated cellulose, and CNC showed crystallinities of 38.7%, 51.2%, and 65.3%, respectively. The CNC had lower thermal stability, which was ascribed to the sulphate group present on the CNC surface.

Based on the experimental idea of reverse simulation, a quantitative area of hole was excavated at the sectional center of a wood specimen. The excavation area was 1/32S, 1/16S, 1/8S, 1/4S, and 1/2S (where S represents cross-sectional area of the complete specimen) and stress wave nondestructive testing of six sensors was performed. The stress wave propagation paths were statistically summarized to obtain the stress wave propagation velocity (Va) for two adjacent sensors, the stress wave propagation velocity (Vb) for two separated sensors, and the stress wave propagation velocity (Vc) for two opposite sensors. Furthermore, by analyzing the advantages and disadvantages of grey relation and stepwise discriminant model when both of them were used alone, a coupling model generated from them was established to dispose the test data. The attenuation ratios Ψa, Ψb, and Ψc of stress wave under three propagation paths and their relation ratios Va/Vb, Vb/Vc, and Va/Vc, a total of six groups of measured data, were selected as discriminant factors for the hole area grade of the wood specimen. The verification results showed that the discriminant accuracy of the coupling model was 100%, and it was concluded that the attenuation ratio (Ψb) of the stress wave propagation velocity for two separated sensors had the strongest discriminant ability against cross-sectional area of the specimen.

The kinetics of pyrolysis of apricot stone and its main components, i.e., lignin, cellulose, and hemicellulose, were investigated via distributed activation energy mode. Experiments were done in a thermogravimetric analyzer at heating rates of 10, 20, 30, and 40 K·min-1 under nitrogen. The activation energy distribution peaks for the apricot stone, lignin, cellulose, and hemicellulose were centered at 246, 318, 364, and 170 kJ·mol-1, respectively. The activation energy distribution for the apricot stone slightly changed; lignin exhibited the widest distribution; and cellulose exhibited the highest activation energy at a conversion degree (α) of less than 0.75. At low pyrolysis temperatures (400 K to 600 K), the pyrolysis of hemicellulose was the main pyrolysis reaction. The apparent activation energy for the apricot stone mainly depended on the pyrolysis of hemicellulose and a small amount of lignin, and the activation energy was low in the early stage of pyrolysis. With the continuous increase in the pyrolysis temperatures (600 K to 660 K), the thermal weight loss of cellulose and lignin was intense. The apparent activation energy for the apricot stone mainly resulted from the pyrolysis of cellulose and lignin, and a higher activation energy was observed in the later stage of pyrolysis.

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.