Research Articles

Color changes caused by artificial UV radiation of Moso bamboo (Phyllostachys pubescens Mazel) were recorded as a function of exposure time to obtain the maximum absorption trend by the Kubelka-Munk (K-M) spectra. Lignin photolysis into smaller molecules was evaluated using spectrophotometry and gas chromatography-mass spectrometry (GC-MS) analysis. Results showed that the K-M absorption peak increased in the yellow and red regions (360 to 500 nm) when compared with the untreated sample, which was in accordance with the yellow-red shift by visual observation. The maximum absorption of the K-M spectra from UVB phototreated bamboo was in the UV region. GC-MS analysis showed that benzene carbonyls, organic acid, and esters were the major types of photolysized molecules of bamboo lignin, which were derived from the C-C bonds adjacent to the α-carbonyl. UV irradiation (295 to 400 nm) resulted in the breakdown of carbonyl and unsaturated C-C groups conjugated to aromatic ring at the C_α ., which partly contributed to the quick discoloration at the initial 100 h of UV irradiation.

An extracellular xylanase was purified from the mesophilic fungus Penicillium rolfsii c3-2(1) IBRL. After three consecutive purification steps, the extracellular cellulase-free xylanase was successfully purified to homogeneity with a recovery yield of 24%. A single protein band of 35 kDa was detected by SDS-PAGE, which had an optimum catalytic activity at pH 5.0 and 50 °C. This purified enzyme was stable at pH 5 to 7, thermostable up to 55 °C, and retained up to 83% of its activity after 4 hours of pre-incubation. A kinetic study yielded estimated Km and Vmax values of 5.73 mg/mL and 691.6 µmol/min/mg, respectively. Thin layer chromatography experiments showed that the purified xylanase was capable of hydrolyzing xylotriose, xylotetraose, xylopentaose, and xylohexaose but not xylobiose, suggesting it is an endo-xylanase. Enzymatic hydrolysis of oil palm trunk residues by commercial enzymes supplemented with the purified xylanase showed a considerable increase in total sugar conversion compared with the commercial enzymes alone, suggesting that xylanase is a key enzyme in the hydrolysis of oil palm trunk residues.

Pressed composites can be produced from wood sawdust waste using modified yeast biomass, waste as a bio-adhesive, ultra-dispersed bacterial cellulose (UBC) as a binder, and preliminary chemical cross-linking. The materials obtained were not inferior to traditional materials based on the required levels of toxic phenol-formaldehyde resin and physical and mechanical parameters. Physical and mechanical properties of the materials depended on the amount and viscosity of the binder, as well as on the chemical structure and conditions of chemical cross-linking and modified UBC application. The strengths of the best examples of the materials obtained were approximately 17 to 20 MPa, the densities were in the range of 1207 to 1255 kg/m3, and the water absorption was less than 20%. During hot pressing, notable changes were observed in the wood particles at FTIR-ATR spectra frequencies of 3620 cm-1, 3600 to 3000 cm-1, 2920 cm-1, 2850 cm-1, 1770 cm-1, 1650 cm-1, 1560 cm-1, and 1089 cm-1. This is mainly due to the chemical and structural changes in lignin, hemicellulose, and binder.

The effect of varying the number of saw blade teeth while transversally cutting beech (Fagus sylvatica L.) wood on the noise level and saw blade lifetime between two sharpenings was tested. The experiment was carried out with raw beech wood samples with dimensions of 25 x 100 x 1000 mm and circular saw blades with cemented carbide tips (24, 40, and 60 teeth). The saw blade diameters were identical (D = 250 mm), as were the cutting wedge angle geometries (α = 15°, β = 60°, γ = 15°). The saw blades were selected based on commonly used blades (in the Czech Republic and Slovakia) for the transversal cutting of the given wood species. Neither the cutting speed (vc = 62 m/s) nor the feed force (Fp = 75 N) were changed during the cutting process. The results suggest that the number of saw blade teeth is an important factor that affects the noise level of saw blade during sawing as well as the wear of cutting edge.

This paper presents some of the properties of commercially manufactured laminated flooring having magnesium oxide substrate. Laminated flooring samples with thin veneer of walnut wood and linoleum were tested for their bending characteristics, internal bonding strength, thickness swelling, and surface roughness. The highest modulus of elasticity value of 583,000 psi was found for the samples loaded in the direction of wood veneer overlay. Linoleum overlaid samples resulted in 461,000 psi for the corresponding value. Wood overlaid samples also showed 8% lower internal bond strength values than those of linoleum laminated specimens. Based on the roughness evaluation of the samples conditioned at 55% and 95% relative humidity levels employing a stylus type equipment, no significant adverse effect of high humidity exposure on their surface quality was determined. It appears that magnesium panels overlaid with solid wood and linoleum veneer sheets could serve as value-added flooring with acceptable properties.

To investigate the effect of temperature on the dynamic sorptive and hygroexpansive behavior of wood, poplar (Populus euramericana cv.) specimens, 20 mm in radial (R) and tangential (T) directions with two thicknesses of 4 mm and 10 mm along the grain, were exposed to a sinusoidally varying relative humidity between 45 and 75% for 1, 6, and 24 h at 25 and 40 °C. Moisture changes, as well as radial and tangential dimensional changes measured during cycling, produced the following results: moisture and dimensional changes in the specimens were generally sinusoidal, and an increase in temperature led to decreased moisture contents and transverse dimensions, accordingly. The amplitude of moisture and dimensional changes was in positive correlation with temperature, while the phase lag was inversely related to temperature. Sorption hysteresis and swelling hysteresis decreased as temperature increased. Both moisture sorption coefficient (MSC) and humidity expansion coefficient (HEC) were supposed to share the approximate value for different thick specimens if cyclic period is sufficiently long. Transverse anisotropy could be found under dynamic conditions, and the T/R was about 1.65 to 1.75, varying sinusoidally with a phase difference of about a half cycle to the imposed relative humidity.

The waste powder produced during the manufacture of marble, which is presently mostly discarded in landfills, has the potential for higher-valued usage. Recycling marble waste powder will contribute to the protection of nature as well as economic gain. The potential use of waste marble powder as filler in the adhesive for manufacturing of laminated veneer lumber (LVL) was investigated in this study. With this objective, LVL panels were manufactured by adding marble factory waste powder in different ratios to polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives. The waste powders of beige marbles and travertine marbles were mixed by weight with adhesives in the percentage levels of 0%, 10%, 20%, 30%, 40%, and 50%. Physical and mechanical tests were performed on the specimens obtained from the LVL panels. According to the results obtained from the present study, as compared to the control specimens, higher mechanical performance was obtained with the waste beige marble powder at high contents and with the waste travertine marble powder at low contents with the PVA adhesive. A poorer mechanical performance was found in the travertine powder with the UF adhesive. The dimensional stability of LVLs containing travertine powder was better than that of the LVLs containing beige marble powder.

Extracting lignin from black liquor is an attractive option in modern pulp mills as a unit process for a combined biorefinery. The lignin obtained can be utilized as solid fuel or other high-value added products. The precipitation equilibrium of kraft lignin from softwood black liquor was studied in this work. It was found that with decreasing pH and temperature, or increasing ion strength, the solid yield increases. Moreover, precipitated softwood kraft lignin has a higher molecular weight and contains lower amounts of carbohydrates and phenolic groups than lignin precipitated from mixed hardwood/softwood black liquor. The content of methoxyl groups in softwood kraft lignin was found to decrease with increasing precipitation yield. An empirical model for estimating the precipitation yield of lignin was proposed and evaluated.

Seven kinds of pyroligneous acids were collected at different temperature ranges (K7-1: 90 to 140 ºC ; K7-2: 140 to 190 ºC; K7-3: 190 to 240 ºC; K7-4: 240 to 290 ºC; K7-5: 290 to 340 ºC; K7-6: 340 to 440 ºC; and K7-7: 440 to 480 ºC). The chemical compositions of the pyroligneous acids were determined by GC-MS. Moreover, the biological activities of pyroligneous acids were investigated by a foliar spray experiment of rape using the pyroligneous acids collected at 90 to 480 ºC. The physiological and chemical responses of pyroligneous acids, including the content of soluble protein and the superoxide dismutase (SOD) activity, were detected. The results of GC-MS analysis showed that the chemical profiles of pyroligneous acids varied with pyrolysis temperature. About 62 kinds of compounds belonging to 8 groups were identified, including ketones, phenols, organic acids, ester, benzene and its derivatives, aldehydes, alcohols, and sugar derivatives. Finally, the pyroligneous acids from walnut shell were applied in foliar spray for rape (Brassica campestris L.). The results demonstrated that pyroligneous acid from walnut shell with a low concentration significantly enhanced the content of soluble protein and the activity of SOD in rape leaves.

In this work, the surface of oil palm mesocarp fiber (OPMF) was modified via alkaline-peroxide treatment with hydrogen peroxide under alkaline conditions. The effect of the treatment on the chemical composition and microstructure of the fiber was examined using chemical analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. The treatment resulted in the removal of lignin, hemicellulose, and waxy substances from the fiber and increased its surface roughness and crystallinity. The eco-friendly biocomposite was made from poly(butylene succinate) (PBS) and chemically treated fiber at a weight ratio of 30:70, and was fabricated via a melt-blending technique followed by hot-pressed moulding. The results indicated that alkaline-peroxide treatment of the fiber improved the tensile strength, tensile modulus, and elongation at break of the OPMF/PBS biocomposite by 54, 830, and 43%, respectively. The SEM analysis revealed improvement of the interfacial adhesion between the chemically treated fiber and the PBS. This work demonstrates that alkaline-peroxide treatment of fiber is beneficial prior to its use in fabricating biocomposites.