Research Articles

The objective of this research was to investigate the effects of some impregnation materials and varnishes on the thermal conductivity of oak wood. Ammonium sulfate, borax, boric acid, zinc chloride, diammonium phosphate, and sodium silicate as impregnation chemicals and polyurethane, cellulosic, synthetic, coloured varnishes and cellulosic, synthetic, industrial paints as finishes were used. The wood materials were impregnated by using the vacuum-pressure method. The thermal conductivity test was performed based on the ASTM C 1113-99 hot-wire method. Results showed that the impregnation chemicals increased the thermal conductivity. The highest values were obtained with boric acid and sodium silicate. In addition, the thermal conductivity of painted oak was higher than that of varnished oak. The lowest thermal conductivity of 0.1465 Kcal/mh°C was obtained with the oak control. The highest thermal conductivity of 0.1756 Kcal/mh°C was obtained when oak was painted with industrial paint and impregnated with boric acid.

Near infrared (NIR) spectroscopy method was introduced to measure the lignin content in Acacia species. Acid-soluble lignin, Klason lignin, and total lignin contents from 78 wood meal samples of Acacia spp. trees grown in Guangxi province with different ages, height, and families were measured by wet chemistry. NIR spectra were also collected using a Bruker MPA spectrometer within 4000-12500cm-1 of wavenumbers using a standard sample cup and split into calibration and prediction sets. Equations were developed using partial least squares (PLS) regression and cross validation for multivariate calibration in this study. High coefficients of determination (R2) and low root mean square errors of cross-validation (RMSECV) were obtained for Klason lignin (R2=0.94, RMSECV=0.398), acid-soluble lignin (R2=0.87, RMSECV=0.144), and total lignin (R2=0.91, RMSECV=0.448) from wood meal. High correlation coefficients were found between laboratory and predicted values for Klason lignin, acid-soluble lignin, and total lignin contents, with R2 and RMSEP values ranging from 0.67 to 0.94, and 0.19 to 0.526, respectively. The study showed that NIR analysis can be reliably used to predict lignin content in Acacia spp.

Water hyacinth (Eichhornia crassipes) biomass has been used for many years for the remediation of heavy metals. The present study successfully utilizes the dried powdered biomass of the aerial part (stem and leaves) of water hyacinth for biosorption of hexavalent chromium. The effect of various parameters (viz. pH, initial metal ion concentration and temperature) on the removal of Cr(VI) was studied by conducting only 15 sets of sorption runs using Box-Behnken Design (BBD). The pH had a negative and temperature and concentration had positive effects on uptake of chromium. The predicted results (obtained using an empirical linear polynomial model) were found to be in good agreement (R2 = 99.8%) with the experimental results. The predicted maximum removal of Cr(VI) (91.5181 mg/g) can be achieved at pH 2.0, initial metal ion concentration 300 mg/L, and temperature 40 °C. The sorption capacity of sorbent was also calculated using a Langmuir sorption isotherm model and was found to be 101 mg/g at 40 °C and pH 2.0.

An analysis of the chemical composition and anatomical structure of banana pseudo-stem was carried out using Light Microscopy (LM), Scanning Electron Microscopy (SEM), and Confocal Laser Scanning Microscopy (CLSM). The chemical analysis indicated there is a high holocellulose content and low lignin content in banana pseudo-stem compared with some other non-wood fiber resources. These results demonstrate that the banana pseudo-stem has potential value for pulping. In addition, we report for the first time from using LM and CLSM that banana stems possess a structure involving helicoidal fibers separated by barrier films.

This study was carried out to determine the changes of the surface color of Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis Lipsky) woods after exterior conditioning. First, the samples were bleached with 25% NaOH and 17.5% H2O2. Afterwards, they were varnished with polyurethane and synthetic varnishes, and then they were exposed to exterior conditions for 12 months. Tests for color differences and metric chroma were done according to the ASTM D-2244 standard. It was deduced that exposure to exterior conditions causes color differences in samples, while bleaching with the given solution reduces that effects, and reverts the surface color to that of the natural control specimens. However, bleached specimens exposed to 12 months exterior conditioning had more discoloration than those of natural control samples. In conclusion, if the wood materials will be exposed to outdoors after bleaching, finishing process should be applied to surfaces in order to prevent further color change.

Unprotected wood exposed outdoors suffers from photodegradation due to absorption of UV light by lignin and dimensional changes because of moisture absorption or desorption by free hydroxyl groups in wood constituents. Chemical modification of cell wall polymers is one of the effective methods of inducing dimensional stability and UV resistance in wood. In this work, etherification of Scots pine (Pinus sylvestris L.) was carried out with alkylene epoxides. Extracted blocks of Scots pine were modified with propylene oxide (PO) and butylene oxide (BO) between 30 and 75 oC for different durations and under varying alkaline conditions. Different weight percent gains (WPG) were obtained. WPG increased with temperature, reaction time, and NaOH concentration. The dimensional stability, mechanical properties, and UV resistance of chemically modified wood were evaluated. Etherified wood exhibited an improvement in dimensional stability, but the efficacy dropped with successive water-soaking, oven-drying cycles, indicating a loss of modifying chemical. After four soak-dry cycles, both modifications retained positive anti-swelling efficiency (ASE) values; however, at WPG values >30%, the PO modified material exhibited a reduction in ASE, indicating cell wall degradation. Both PO and BO modified wood exhibited a loss in static mechanical properties measured as modulus of elasticity and modulus of rupture, with the reduction being dependent upon the level of modification. Modification of wood with PO provided partial photo stability to wood polymers, whereas BO was more promising in improving dimensional stability.

The chemical degradations of highly-purified cellotriose, cellotetraose, and cellopentaose in H2O2 and NaOH media were studied, respectively. The degradation products were analyzed by HPLC, FTIR, and GC-MS techniques. The results show that for the three oligosaccharides the main oxidative degradation products are 2, 3-dihydroxy-butanedioic acid, 2-keto-gluconic acid, glucopyranose, D-glucose, D-gluconic acid, and cellooligosaccharides with lower DP. A small amount of arabinose is formed during the oxidation of cellotriose. The main alkaline degradation products for the three oligomers include 3-deoxy-isosaccharinic acid-1,4-lactone and 3-deoxy-hexonic acid-1,4-lactone. Arabinose coumpounds are found to be an accidental degradation product of cellotriose. Finally, the possible formation mechanisms are proposed, including 2,3-dihydroxy-butanedioic acid, 2-keto-gluconic acid, D-gluconic acid, arabinose, 3-deoxy-isosaccharinic acid-1,4-lactone, and 3-deoxy-hexonic acid-1,4-lactone. The radical attack from H2O2 is probably at the glycosidic linkage, resulting in the formation of a series of degradation products. Degradations of cellooligosaccharides in alkaline solution are elucidated to follow an enediol anion reaction mechanism.

The production of cellulases, hemicellulases, and starch-degrading enzymes by the thermophilic aerobic fungus Talaromyces emersonii under liquid state culture on various food wastes was investigated. A comprehensive enzyme screening was conducted, which resulted in the identification of spent tea leaves as a potential substrate for hydrolytic enzyme production. The potent, polysaccharide-degrading enzyme-rich cocktail produced when tea leaves were utilised as sole carbon source was analysed at a protein and mRNA level and shown to exhibit high level production of key cellulose and hemicellulose degrading enzymes. As presented in this paper, the crude enzyme preparation produced after 120 h growth of Talaromyces emersonii on used tea leaves is capable of hydrolysing other lignocellulosic materials into their component monosaccharides, generating high value sugar syrups with a host of industrial applications including conversion to fuels and chemicals.

The flexural properties of commercial bagasse-filled polyethylene (PE) and polypropylene (PP) composites were determined as a function of strain rate at room temperature. The applied strain rates were 1.5 ×10-4, 3.75×10-4, 7.5×10-4, and 1.5×10-3 s-1. The flexural modulus tended to increase linearly for the two types of composites with the logarithm of strain rate. The bending strength of polypropylene composite also behaved in a similar manner, but the polyethylene composite exhibited different behavior in which the MOR values of polyethylene composite didn’t alter appreciably as a function of strain rate. The flexural response of a polypropylene-based composite was found to exhibit higher dependency on strain rate than a polyethylene-based composite. Water absorption of both composites followed the kinetics of a Fickian diffusion process. Water absorption and dimensional instability of PE-based composites were lower than those of PP-based composites. The highest swelling took place in the thickness of the samples, followed by the width and length, respectively.

Cellulose fibres from sugarcane bagasse were bleached and modified by zirconium oxychloride in order to improve the mechanical properties of composites with high density polyethylene (HDPE). The mechanical properties of the composites prepared from chemically modified cellulose fibres were found to increase compared to those of bleached fibres. Tensile strengths of the composites showed a decreasing trend with increasing filler content. However, the values for the chemically modified cellulose fibres/HDPE composites at all mixing ratios were found to be higher than that of neat HDPE. Results of water immersion tests showed that the water absorption affected the mechanical properties. The fracture surfaces of the composites were recorded using scanning electron microscopy (SEM). The SEM micrographs revealed that interfacial bonding between the modified filler and the matrix was significantly improved by the fibre modification.