Research Articles

This study investigated the morphology, electrochemical modification with respect to the wood fiber direction, and mechanical properties of wood modified by in situ polymerization with polyaniline (PANI). This polymerization formed a composite material with applications as an anti-static, electromagnetic, anti-corrosion, and heavy metal purifying materials. The polymer was found throughout the entire structure of the wood and was quantified within the wood cell wall and middle lamella by SEM-EDX. The presence of PANI affected the conductivity of the composite specimens, which was found to be higher in the fiber direction, indicating a more intact percolation pathway of connected PANI particles in this direction. The PANI modification resulted in a small reduction of the storage modulus, the maximum strength, and the ductility of the wood, with decreases in the properties of specimens conditioned in an environment above 66% relative humidity. The in situ-polymerized PANI strongly interacted with the lignin component of the veneers, according to the decrease in the lignin glass transition temperature (Tg) noted in DMA studies.

During sequential bleaching operations, pulp fiber properties are gradually changed due to mechanical and chemical treatments. In this study, the correlations between pulp or fiber properties such as kappa number, viscosity, total charge, fiber length, and zero-span tensile strength as well as Scott bond of elemental chlorine free (ECF) bleached softwood kraft pulps was investigated. The influence of zero-span tensile strength and Scott bond on tensile and tear strength was also discussed. The Scott bond and zero-span tensile strength showed a strong logarithmic correlation with pulp kappa number and pulp viscosity, while the regression coefficient for Scott bond was negative. An overall deterioration of paper tensile and tear strength from pulps whether beaten or not were observed along the multi-stage ECF bleaching operations. Changing contributions to sheet tensile or tear strength could be mostly attributed to changes in zero-span tensile strength rather than Scott bond during ECF bleaching.

The characteristics of gutta-percha (i.e., chemical compound and melting and glass transition temperatures) and the performance of laminated wood (i.e., moisture content, density, shear strength, and delamination ratio) prepared from sengon wood (Paraserianthes falcataria L. Nielsen) bonded with a gutta-percha-based adhesive were investigated. The gutta-percha-based adhesive was prepared by modification of gutta-percha with 5% maleic anhydride (MAH) and 0.75% benzoyl peroxide (BPO) at various gutta-percha to toluene ratios (w/w) (i.e.,15:85; 17.5:82.5; 20:80; and 22.5:77.5), followed by heating at 70 °C in a water bath for 10 min. Laminated wood was manufactured using both modified and unmodified gutta-percha-based adhesives at 250 gm-2 of glue spread and clamped for 24 h. Terpenes, especially 1,3 butadiene, 2-methyl (CAS)-isoprene (trans 1,4- isoprene) (polyterpene), were found to be the dominant chemical component of gutta-percha. The glass transition and melting temperatures of gutta-percha were -56.75 °C and 51.67 °C, respectively. The modification of gutta-percha with MAH and BPO as an initiator resulted in improved performance for the laminated wood. Infra-red spectrometry of the modified gutta-percha-based adhesive showed a new peak at 1720 cm-1, indicating the C=O bond of MAH.

This work reports on the exploitation of Beta vulgaris for biosurfactant production by Bacillus licheniformis STK 01 and its optimization using statistical modeling of response surface methodology (RSM). Three variables were investigated: agro-waste concentration, pH, and temperature. The response and contour plots of the RSM showed perfect interaction among the variables, with the highest surface tension reduction of the culture medium to 30 mN/m observed at 42 °C, a pH of 8, and a substrate concentration of 4% (w/v). The biosurfactant produced demonstrated a high tendency for hydrocarbon emulsification. Furthermore, by numerical optimization techniques, the optimum conditions were found to be as follows: a pH of 6.72, an agro-waste concentration of 4% (w/v), and a temperature of 44.5 °C. The experiment conducted to validate the optimum conditions obtained showed a biosurfactant with remarkable surface activity, lowering the surface tension of the broth to 30 mN/m, when the organism was grown on B. vulgaris, and to 23.5 mN/m, when grown in glucose medium – the later representing one of the highest surface tension reductions ever reported for a biosurfactant. This study revealed, among others, that the exclusive utilization of cheap solid agro-waste without supplementation with a refined nutrient source is feasible and could ensure the economic sustainability of biosurfactant production.

There is an urgent need for a biodegradable, hydrophobic material that can be used in developing packaging materials. In this preliminary study, epicuticular wax has been extracted from the leaves of Calotropis procera and Alstonia scholaris using various solvents (i.e., ethanol, methanol, benzene, and acetone). The highest wax amounts were found to be 0.54 µg/cm² and 0.13 µg/cm² from Alstonia scholaris and Calotropis procera, respectively. The highest hydrophobicity (29.57%) was found to be in paper discs coated with epicuticular wax extracted with benzene from the adaxial surface of Calotropis procera.

In this paper, the NaOH pretreatment of banana pseudo-stem fiber for biogas production was investigated using a statistically designed set of experiments. A central composite design was used to identify the optimum pretreatment condition for four factors, i.e., NaOH concentration, pretreatment temperature, pretreatment time, and fiber length, on biogas fermentation of banana pseudo-stem fiber. The best pretreatment condition was 7.8% NaOH, 0.2-cm fiber length, and a temperature of 48 °C for 3 days. NaOH pretreatment increased the biogas yield of banana pseudo-stem fiber. The highest biogas yield was 463.0 mL·g^-1VSadded, which was 89.2% higher than that of the control, at 244.7 mL·g^-1VSadded.

We investigated the influence of an additional mass bonded on a wooden bar on its apparent Young’s modulus based on a longitudinal vibration theory. Rectangular bars of Sitka spruce (Picea sitchensis Carr.) were used as experimental materials. After bonding an iron piece on a bar, a free-free longitudinal vibration test was performed to obtain the Young’s modulus. Modal analysis was also performed to examine the effect of a knot on the measured Young’s modulus. The Young’s modulus decreased with an increase in mass of iron pieces bonded on the specimen and that in a size of the knot, since the constants required for the frequency equation of longitudinal vibration changed due to the additional mass and the knot. An equation was developed which contains the effects of the mass and position of the iron piece on the constants. The Young’s moduli calculated by this equation resembled the values without an iron piece and the knot. Assuming a knot to be the additional mass, the estimation method used to examine the effect of a knot on the apparent Young’s modulus was proposed. The analysis showed that the higher the resonance mode and the nearer the position to an end, the more effective efforts to reduce the effect of the additional mass will be.

Woody (Albizia pedicellaris and Terminalia ivorensis) and non-woody (guinea corn (Sorghum bicolor)) glume and stalk biomass resources from Nigeria were subjected to thermo-analytical and physico-chemical analyses to determine their suitability for thermochemical processing. They were found to have comparably high calorific values (between 16.4 and 20.1 MJ kg-1). The woody biomass had very low ash content (0.32%), while the non-woody biomass had relatively high ash content (7.54%). Thermogravimetric analysis (TGA) of the test samples showed significant variation in the decomposition behavior of the individual biomasses. Gas chromatography/mass spectrometry (GC/MS) of fatty acid methyl esters (FAMEs) derivatives indicated the presence of fatty and resin acids in the dichloromethane (CH2Cl2) extracts. Analytical pyrolysis (Py-GC/MS) of the samples revealed that the volatiles liberated consisted mostly of acids, alcohols, ketones, phenols, and sugar derivatives. These biomass types were deemed suitable for biofuel applications.

A white-rot fungus, Phlebia sp. MG-60, was applied to the fermentation of high-solid loadings of unbleached hardwood kraft pulp (UHKP) without the addition of commercial cellulase. From 4.7% UHKP, 19.6 g L^-1 ethanol was produced, equivalent to 61.7% of the theoretical maximum. The highest ethanol concentration (25.9 g L^-1, or 46.7% of the theoretical maximum) was observed in the culture containing 9.1% UHKP. The highest filter paper activity (FPase) was observed in the culture containing 4.7% UHKP, while the production of FPase in the 16.5% UHKP culture was very low. Temporarily removing the silicone plug from Erlenmeyer flasks, which relieved the pressure and allowed a small amount of aeration, improved the yield of ethanol produced from the 9.1% UHKP, which reached as high as 37.3 g L^-1. These results indicated that production of cellulase and ensuing saccharification and fermentation by Phlebia sp. MG-60 is affected by water content and benefits from a small amount of aeration.

Wood-derived bio-oil was used to decrease formaldehyde emissions from urea-formaldehyde (UF) resin during the process of making three-layered plywood. The obtained bio-oil urea formaldehyde (BUF) resins were characterized by their physical, chemical, and mechanical properties (e.g., viscosity, solid content, pH value, shelf life, formaldehyde emissions, and bonding strength), analyzed for their specifications, and characterized with Fourier transform infrared spectroscopy and thermogravimetric analysis. The synthesized resins were further employed to prepare the plywood with the veneers glued. The resulting BUF plywood displayed much lower formaldehyde emissions and comparable bonding strength. For the modification on formaldehyde emission of the plywood, it was concluded that the bio-oil can be used to effectively reduce formaldehyde emissions from UF wood adhesive.