Research Articles

The mechanical properties of unidirectional oil palm empty fruit bunch (OPEFB) fibre / polypropylene (PP) composites were analysed. The composites were fabricated with unidirectional fibre orientations of 0°, 45°, and 90°, with mass fractions of 25%, 35%, and 45% for each fibre orientation angle. The composites were then subjected to tensile, flexural, and impact testing. Superior tensile, flexural, and impact strengths were observed for the unidirectional composites with 0° fibre orientation angle. A fibre loading of 35% provided the highest tensile strength, while fibre loadings of 25% and 45% yielded the greatest flexural and impact resistances, respectively. The crash performance of the unidirectional composite subjected to low-velocity impact in the automotive bumper fascia was investigated. The composite exhibited significantly improved energy absorption capability and comparable specific energy absorption when compared with the current material being used for the bumper fascia.

Three modified surface-sizing agents (SA) for paper were synthesized by the cross-linking of collagen with either glycol diglycidyl ether (GDE), tetrahydrophthalate diglycidyl ester (TDE), or triglycidyl p-aminophenol (TP) and then grafting with butyl acrylate (BA). The performance and application of the sizing agent emulsions were characterized and tested. The GDE-SA had the highest viscosity. The GDE-SA coated corrugated paper had the best water resistance, smoothness, and physical and mechanical properties.

A test method was developed to evaluate the surface characteristics of veneers produced using the peeling process. Rotary cut Scots pine (Pinus sylvestris L.) veneers, which were produced from logs soaked at 65 °C for 42 h prior to peeling and dried at 125 °C, were used as the test specimens. The pine veneers were produced under industrial conditions. The density variation of the round wood was determined using X-ray computed tomography, the thickness variation of the pine veneers was measured using an optical microscope, and the structure of the veneers was examined using a scanning electron microscope. The pine wood was characterised by the density variation in the transverse section. At the same moisture level, broad-ring pith-adjacent juvenile sapwood had a lower density compared with that of perimeter-adjacent mature wood. The clear lack of density homogeneity was seen in the width of the subsequent annual growths. The roughness of the pine veneers demonstrated significant variation, depending on the tool angle (17° and 21°), wood area (sapwood and heartwood), and veneer side (tight and loose). The veneer thickness had a significant impact on the roughness values measured perpendicular to the grain.

Stenotrophomonas maltophilia is a microorganism that exhibits a wide range of applications. In this study, a Box-Behnken design was used to determine the optimum parameters for maximizing the cellulase production by S. maltophilia isolated from soil. The factors that were evaluated were the pH (3 to 10), carbon source (0.5 wt.% to 1.5 wt.% carboxymethylcellulose), and nitrogen source (0.5 wt.% to 1.5 wt.% yeast extract). The results showed that a maximum cellulase activity of 0.082 U/mL was achieved at a pH of 6.3, a 0.72% carbon source concentration, and a 1.5% nitrogen source concentration. Stenotrophomonas maltophilia was grown on sterilized wheat straw (WS) to evaluate the production of reducing sugars as a potential application in a biorefinery scheme. After 72 h of incubation at 30 °C, the final concentration of reducing sugars was 150 mg/L ± 2 mg/L and the corresponding yield was 10.16%. The hydrolyzed WS was mapped by synchrotron micro Fourier transform infrared spectroscopy, where a significant reduction in the characteristic signals for hemicellulose and cellulose was observed.

Microcapsules of neem extract (MNE) were observed using an optical microscope (OM) and scanning electron microscope (SEM). The antifungal activity of the extract was evaluated by an agar diffusion assay. The MNE were induced into the wood material by a full-cell process. The diameters of the microcapsules were measured by OM, and the distribution of microcapsules in wood was observed by SEM. Wood blocks of Populus tomentosa were treated with the MNE, neem extract (NE), and an acid mixture of melamine formaldehyde resin (MF) and sodium dodecyl sulfate (AMS); their antifungal properties against Penicillium citrinum, Trichoderma virens, and Aspergillus niger were visually assessed. The microcapsules prepared by MF, 1% sodium dodecyl sulfate (SDS), and 10% NH4Cl showed regular shape and good dispersion. The agar diffusion assay showed that the neem extract had significant inhibition against all tested fungi, and the optimum concentration of NE was 10%. The diameters of the microcapsules were normally distributed in a range of 0.4 μm to 4 μm, and the microcapsules were unevenly distributed in the vessels and surface of Populus tomentosa. Wood specimens treated with MNE observed complete inhibition to all studied fungi, and the mark grades of specimens treated with MNE against three fungi all reached 5 (no growth of fungi).

The objective of this study was to investigate the physical and mechanical properties of strandboard made from the residual veneer material of rubber wood (Hevea brasiliensis Müll. Arg.) and falcata wood (Falcataria moluccana). The study investigated five different ratios of rubber and falcata (100:0; 75:25; 50:50; 25:75; 0:100). Random strandboards were made at a target density of 600 kg m^-3 using phenol formaldehyde (PF) as resin. All panels were tested through static bending (MOE/MOR). The internal bonding, thickness swelling, and water absorption of the strandboards were also examined. Results showed that the incorporation of the rubber and falcata ratio of 25:75 was substantially greater than the other ratios. The samples using other ratios for MOR, MOE, and physical properties obtained slightly lower mean values compared to the sample with the ratio of 25:75 (rubber and falcata).  Based on these results, strandboards obtained from rubber and falcata have the potential to be commercialized.

Common ash (Fraxinus excelsior L.) wood was heat treated in an oven at temperatures of 160, 180, and 200 ºC, and under atmospheric pressure in the presence of air for a duration of 3, 6, 9, and 12 h. The impact of heat treatment on the chemical composition of wood was studied. The extractives content initially increased up to 200 ºC and 3 h. However, with extended treatment duration it decreased. Hemicellulosic monosaccharide (D-xylose) degraded under all treatment conditions and resulted in a decrease of holocellulose content. In the case of lignin, demethoxylation and the formation of more condensed structures were observed. This led to an increase in lignin content at temperatures of 180 and 200 ºC. The oxidation process already began at 160 °C. This resulted in the formation of new carbonyl or carboxyl groups that contributed to color change, i.e., wood darkening. From the beginning the increase in the cellulose crystallinity was observed, and then it decreased. The maximum was reached at the temperatures of 160, and 180 °C for 9 h of treatment and at the temperature of 200 °C for 6 h.

The differences of physical-mechanical properties in heartwood and sapwood of Toona sp. wood (Toona ciliata M. Roem.) were compared before and after an accelerated aging treatment, which was conducted in accordance with ASTM (American Society for Testing and Materials) standards. The results revealed that the physical-mechanical properties of heartwood were better than those of sapwood. The accelerated aging treatment weakened the physical-mechanical properties of the wood samples. During the aging treatment, the carbohydrates in the cell wall, including cellulose and hemicellulose, were depolymerized; as such, the crystallinity of cellulose was decreased by aging. The depolymerization of carbohydrates and the reduction of crystalline contributed to decreasing the physical-mechanical properties of the wood samples.

Steam treatment was used in this work to correct the observed warp in dried core-wood radiata pine (Pinus radiata) lumber that appears during the industrial drying process at high temperatures. The experimental design considered seven tests and three process variables: temperature, overload, and treatment time. The warp and moisture content before and after the treatment were measured, which allowed for assessing the efficiency of the cup recovery process of the studied thermal treatment programs. Of the analyzed types of warp (twist, bow, crook and cup), only twist was observed to be relevant to the effects of the permissible wood quality classification. The results showed that the twist recovery depends on the temperature, treatment time and overload magnitude. The best treatment results were with a steaming temperature of 100 (°C) and an overload of 3 (ton/m³) applied for 6 (h), which allowed an average recovery value of approximately 43.1%. Moreover, there was an increase in the moisture content and wood density of 10% and 3%, respectively. Finally, the post-treatment of wood with superheated steam did not show a significant improvement to the warp recovery.

Nanocrystalline cellulose was prepared from bleached softwood kraft pulp using acid hydrolysis. Acetylated nanocellulose (AcNCC) and polylactic acid (PLA) were mixed together at different proportions under certain humidity conditions using a miscible method to prepare highly regular porous AcNCC/PLA composite films. The composites were characterized using scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The PLA/Ac-NCC-4 showed a uniform pore diameter distribution with diameter of 1.0 μm to 5.0 μm. The mechanical properties and thermal stability of the PLA composites were improved with the addition of AcNCC. The pore structure was regular and well distributed. When the AcNCC loading was 4%, the tensile strength and Young’s modulus of the composites were 2.07 and 2.41 times higher than that of the pure PLA, respectively. The composites also exhibited high visible light transmission.