Research Articles

A long-term onsite assessment of the hygrothermal performance of a wood frame wall system is presented in this work. The system was applied in a wood demonstration house within the Lake Tai climate zone of Suzhou, China. The hygrothermal performance of the cavity insulation wall was determined from the temperature, relative humidity, and from the temperature of the wood material surface throughout the year. The results clearly indicated the effect of the cavity insulation, cladding cavity ventilation, and air-vapor barrier. Thermal performance was very good due to the wall cavity insulation. Cladding cavity ventilation was effective at low relative humidity of the insulated wall cavities. Condensation and mold growth were not found inside the wall during the test period. The wood frame wall system had good hygrothermal performance and may be widely used in hot summer and cold winter climate zones in China.

Bamboo is a potential lignocellulosic biomass for the production of bioethanol because of its high cellulose and hemicellulose contents. An acid-free ethanosolv process was proposed to overcome the problems caused by the acid catalysts commonly used in organosolv processes. In this research, ethanosolv pretreatment catalyzed by NaOH was used to enhance the enzymatic saccharification of moso bamboo. The addition of 10% (w/w on bamboo) NaOH in 75% (v/v) ethanol was demonstrated to be effective in the pretreatment and fractionation of bamboo. The pretreatment yielded a solid fraction with 60.1% cellulose. The cellulose-to-glucose conversion yield was 28.9% to 45.1%, depending on pretreatment conditions, after enzymatic hydrolysis of the solid fraction at 50 °C for 48 h using enzyme loading (15 filter paper units of cellulase/g cellulose and 30 IU b-glucosidase/g cellulose). The concentrations of fermentation inhibitors such as 5-hydroxy-2-methyl furfural (HMF) and furfural were negligible in the spent liquor after the ethanosolv pretreatment and were much lower than those in the spent liquor from H2SO4-water or ethanosolv only treatment.

Spent mushroom substrate (SMS), a renewable bio-waste from the mushroom-growing industry, was used as an adsorbent to remove methylene blue (MB) from aqueous solution. SMS was characterized using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Adsorption experiments with the SMS adsorbent were performed based on various parameters, such as adsorbent dose, initial MB dye concentration, initial pH, contact time, and temperature. The Langmuir, Freundlich, and Temkin isotherm models were employed to interpret the adsorption behavior. The results indicated that the equilibrium data were perfectly represented by the Temkin isotherm. The maximum adsorption capacity of SMS reached 63.5 mg g-1 at 303 K. The kinetics studies indicated that the pseudo-second-order model best described the adsorption of MB on SMS. The activation energy of the adsorption was 5.64 kJ mol-1. Thermodynamic parameters suggested that the adsorption was an exothermic and spontaneous physical process. The results imply that SMS is a potentially low-cost adsorbent for treating wastewater containing cationic dyes.

Variations in brown rot decay and proportions of heartwood and sapwood were investigated in eastern white cedar (Thuja occidentalis L.). This experiment tested the hypothesis that the incidence of brown rot decay depends on the site, tree age, tree height, and heartwood/ sapwood ratio. Forty-five trees were sampled and felled from three mature stands in the Abitibi-Témiscamingue region, Quebec, Canada. From each tree, disks were systematically sampled along the entire stem, and the heartwood, sapwood, and decay proportions and volumes were determined for each disk. Scanning electron microscopy showed that growth of fungi causing brown rot decay was limited and slower in latewood than in earlywood due to the narrow cell lumen, thick wall, and limited number of bordered pits in latewood tracheids. Site, tree height, and tree age had significant effects on the proportions of sapwood, heartwood, and decay. Heartwood and brown rot decay proportions decreased from the base of the tree upward, while the sapwood proportion increased. There was more decay in older trees and in those growing on moist versus dry sites; however, decay was not serious in trees younger than 80 years. In addition, brown rot decay proportion correlated strongly and positively with heartwood proportion and tree volume, but negatively with sapwood proportion.

The objective of this study was to evaluate the effect of heat treatment on properties including oven-dry density, weight loss, surface roughness, shear strength, and hardness of eastern red cedar (Juniperus virginiana L.). The anatomical structures of samples were also examined by scanning electron microscope (SEM). Two different heat treatment schedules, with temperatures of 130°C and 160°C and 3 and 7 h exposure times, were considered for the experiment. A stylus method was employed to evaluate the surface properties of heat-treated samples. Three roughness parameters, average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax), were determined from the surface of specimens and used to evaluate the effect of heat treatment on the surface properties. The shear strength of samples bonded with polyvinyl acetate (PVAc) adhesive was also measured. All properties of the samples exposed to different heat treatment schedules were significantly different (p = 0.05) from each other. The results of this study demonstrated that the oven-dry density, surface roughness, shear strength, and hardness of the samples decreased, while their weight loss increased slightly, with increasing heat treatment temperature and time.

The objective of this study was to evaluate properties of experimental particleboard panels manufactured from wheat straw that had been pretreated with acetic anhydride, soapy solution, hot water, or steam. Wheat straw particles were mixed with commercially manufactured wood particles at a ratio of 60%. Control straw particleboards with non-treated straw and wood particles were also produced. The results showed that the pretreatment of wheat straw significantly improved both the physical and mechanical properties of the straw particleboards. Panels made from wheat straw treated with a 9% solution of acetic anhydride or boiled in a soapy solution resulted in the highest mechanical properties, with an increase in bending strength values. Regarding internal bond strength, the samples made from wheat straw particles treated with acetic anhydride and a soapy solution had 2 and 3 times higher values, respectively, than those of non-treated samples. It seems that the pretreatment of wheat straw had a greater effect on the thickness swelling of the specimens than on their water absorption.

Crop straw-reinforced industrial materials can be effectively used as wood replacements, so the nondestructive evaluation of the dynamic performance and the realization of in-service testing are necessary for further quality control. Three nondestructive testing methods based on fast Fourier transform analysis were used to establish the dynamic modulus of elasticity of soybean stalk-reinforced materials. The results were compared to destructive measurements of the static modulus of elasticity and modulus of rupture using a regression analysis method. Significant correlations existed between the dynamic modulus of elasticity, static modulus of elasticity, and modulus of rupture. The highest degree of correlation was obtained from the flexural vibration method. The correlation degree is similar to that between the static modulus of elasticity and the modulus of rupture. Using the regression equation, a performance prediction model was established that will enable the prediction of the mechanical properties and quality evaluation of soybean stalk board.

Because of the increasing awareness of the environment and energy issues, as well as advances in technology, the areas of application for annual plant fiber functional materials are expanding. In this work, two chemical treatments, alkalization (2 h agitation with 5% NaOH) and furfurylation (graft furfuryl alcohol followed by oxidation with (1N) NaClO2 solution), were conducted on Luffa cylindrica fiber surfaces. The grafting of furfuryl alcohol followed by oxidation-generated quinines showed better results than alkaline treatment with respect to enhancement of surface area and hydrophobicity as well as wax, lignin, and hemicellulose extraction. The efficiency of chemical treatments was verified by elemental analysis and FTIR spectroscopy. Differential scanning calorimetry, thermo-gravimetric analysis, scanning electron microscopy, water absorption, and mechanical tests were performed to determine the thermal, mechanical, and morphological properties of untreated and chemically treated luffa fiber reinforced epoxy composites. Microstructures of the composites were examined to determine the mechanisms for the fiber-matrix interaction, which affects the thermal stability, water absorption, and mechanical behavior of the composites. The data from the water absorption process of composites at various temperatures were analyzed using a diffusion model based on Fick’s law.

The charge density of a bleached Kraft hardwood pulp, subjected to layer-by-layer adsorption of the oppositely charged cellulose derivative polyelectrolytes hydroxyethylcellulose ethoxylate, quaternised (HECE), and carboxymethyl cellulose (CMC), was studied by polyelectrolyte titration as a function of pH and ionic strength. The experimental design included a simultaneous variation of the experimental parameters, and the trends were evaluated with the help of partial least squares regression. As expected from the literature, the data indicate that both pH and ionic strength influence the charge of cationic fibers. It is also obvious that CMC as an outermost layer is more sensitive to changes in pH than the deprotonation of ≡COOH groups suggests. High ionic strength seems to be beneficial for the adsorption of HECE, while the pH dependence seems much more complicated. The non-linear pH dependence indicates that, in addition to electrostatic interactions, entropy factors and hydrogen bonding between OH groups on both the substrates and ligands are responsible for the adsorption, which is in agreement with literature on the subject.

The potential of sulfurous acid prehydrolysis followed by chemical pulping was examined at the laboratory scale using radiata pine. The residue obtained by sulfurous acid prehydrolysis with base addition was sufficiently delignified in a subsequent soda pulping stage, while the delignification of the residue was completely insufficient in subsequent kraft pulping. The residues prepared by prehydrolyses of hydrochloric and sulfuric acids were not delignified sufficiently regardless of the pulping method. The yield of hemicellulose-derived monosaccharides was about 90% on a theoretical basis in the optimal sulfurous acid prehydrolysis. In subsequent soda pulping under various conditions, pulps with kappa number 21 to 34, pulp yield 37 to 41%, and high cellulose content could be prepared from the residue obtained by sulfurous acid prehydrolysis with base addition. It was suggested from these results that sulfurous acid prehydrolysis with base addition in combination with subsequent soda pulping is an effective method for the utilization of wood hemicelluloses.