Volume 14 Issue 1

Textile (cotton) dust, which is harmful to humans and the environment, is one of the largest wastes in the textile industry. The aim of this study was to investigate the potential use of this waste in high value-added materials. Physical and mechanical properties and formaldehyde emissions of the three-layered particleboards with textile (cotton) dust in the middle layer were investigated in this study. A phenol formaldehyde resin was used as the binder in particleboard production. Four different amounts of textile dust (10%, 20%, 30%, and 40%) based on the oven-dried weight of the wood were obtained from a commercial textile manufacturer as industrial waste. The density, thickness swelling, modulus of rupture, modulus of elasticity, internal bond, and formaldehyde emissions of the produced panels were determined. The physical and mechanical properties and formaldehyde emissions of the particleboards were negatively affected, which decreased with the addition of a high amount of textile powder. At low rates, the use of textile dust in the middle layer did not significantly decrease the particleboard properties. Textile dust can be a partial solution for the raw material demand of the wood-based panel industry.

Laser machining is an advanced technology that provides efficiency and precision for the processing of wood. In this paper, the ablation mechanism of wood processed via a water-jet assisted nanosecond laser was analyzed. The influences of cutting speed and laser power on the cutting width of northeast China ash wood (NCAW) (Fraxinus mandshurica Rupr.) with and without the water-jet assisted system were evaluated. The surface morphology of the kerf of processed NCAW was observed via scanning electron microscopy (SEM). Furthermore, a factorial design experiment was carried out to analyze the effects of process parameters on the cutting width. Additionally, the experimental results were processed by multilinear regression analysis. The results showed that with the water-jet assisted system, the minimum value of the cutting width was 0.18 mm when the cutting speed was 50 mm/s and the laser power was 6 W, and good surface quality was obtained. The experimental results were processed by an analysis of variance and multilinear regression analysis. The predicted model, effectively validated by the experiments, had good prediction accuracy, which provided a theoretical basis for predicting the cutting width of NCAW processed by a water-jet assisted laser.

Osmotic pressure provided by salty wastewaters is an important influencing factor for alginate-like exopolysaccharides (ALE) in aerobic granular sludge (AGS). Therefore, research on the influence of salinity (NaCl 0 R1, 10 g/L R2, 30 g/L R3) on AGS and its ALE formation was conducted. A salinity of 1% induced larger particle size with smooth spheroidal shape and enhanced granular strength in R2. The TOC and ammonia removal were unaffected in both R2 and R3, but the P removal was greatly enhanced. ALE was much enriched at moderate salinity (1% NaCl). The amount of ALE reached 49.8 mg/g VSS at 140 d in R2, which was much higher than in R1 (26.8 mg/g VSS) and R3 (28.9 mg/g VSS), possibly due to the activation of gene algC expression in AGS of R2. ALE also showed the largest GG block fractionation and MW in R2, which indicated the greatest enhancement of mechanical properties. Moreover, enrichment of glucosamine, lipid content, and octadecanamide derivative in ALE of R2 endowed it with medicinal potential, stronger water-barrier property, and reduction of the products’ friction coefficients, respectively. Therefore, AGS based on ALE is a potential technology for treatment of salty wastewater.

When a lag screw with a large diameter is used as the shear connector in timer-concrete composite beams, the procedure of pre-drilling is required during the construction process. In this paper, a new type of lag screw was proposed to omit the pre-drilling step. To investigate the shear behavior of the self-tapping lag screws for glulam-lightweight concrete composite beams, a total of 18 push-out tests were conducted. Based on the push-out test results, the influences of concrete type, screw diameter, and penetration length of screw into timber on the load-carrying capacity were analyzed in detail. The push-out test results showed that the concrete type had no remarkable effect on the load-carrying capacity. The load-carrying capacity was improved with increased screw diameter and penetration length. In addition, an analytical model for load-carrying capacity of lag screw connectors was proposed based on the push-out test results. By comparisons, it was found that the timber-timber and steel-timber models proposed in Eurocode 5 made very conservative predictions on the load-carrying capacity of lag screws. The results of the analytical method presented in this paper showed a better agreement with the experimental results.

Wooden composites reinforced with advanced engineering materials are promising as building materials. The use of these materials has been increasing in recent years. It is important to understand the behaviour of their deformation under load for optimum design of composite materials. There is limited information about the deformation behaviour of wooden composites under different loads. In this study, strain and displacement distributions were measured for wood structural materials made with glass fibre, carbon fibre, oak (Quercus robur), and polyurethane resin. The digital image correlation method (DIC) was used for this purpose. Deformation behaviours were determined from the images recorded under specific loads in the bending test. There was an increase of 17.3% in bending strength of wood composites with the addition of glass fiber. The cracking process was visualized for different advanced engineering materials. The imagery clearly showed the development of the strain and displacement field. The deformation behaviours of reinforced and unreinforced wood composites were different. The strain distribution of wood composites significantly affected the strength properties.

Effects of alkaline peroxide (AP) treatment on chemical compositions and characteristics of lignocellulosic nanofibrils (LCNFs) were investigated. The AP treatment was conducted on a wood powder (Liriodendron tulipifera) at 80 °C for 1 or 5 h with different hydrogen peroxide concentrations (0.2 to 12 wt%) to selectively remove hemicelluloses and lignin. The treated wood powder was then defibrillated using wet-disk milling (WDM). The hemicelluloses and lignin in the LCNFs were successfully reduced to the ranges of 6.0% to 23.6% and 13.0% to 30.0%, respectively, depending upon the AP treatment conditions. The defibrillation efficiency improved as the hemicelluloses and lignin were removed, which reduced the LCNF dimensions. The filtration time increased with decreasing lignin and hemicellulose contents. The cellulose crystallinity and surface area of the LCNFs increased with decreasing lignin and hemicellulose contents. The tensile strength and water contact angles of the nanopaper handsheets increased, and the paper’s color became whiter as the lignin content decreased.

The aim of this research was to determine the influence of exposure time at 60 °C in the compression strength parallel to the grain (f_c0) and modulus of elasticity in compression parallel to the grain (E_c0) for cupiúba (Goupia glabra), eucalypt (Eucalyptus saligna), garapeira (Apuleia leiocarpa) and jatobá tamarindo (Hymeneae sp.) wood species. The factor investigated in this research was the residence time in kiln (exposure at controlled temperature 60 °C) of specimens: 0 (wood tested at room temperature and moisture content around to 12%), 168, 456, 720, and 2160 hours, simulating the reaction of the material in confined roof structures. Compression parallel to the grain tests were conducted according to the methods of the Brazilian Standard Code ABNT NBR 7190 (1997). ANOVA results indicated that the temperature (60 °C) had a significant influence in the five exposure times. All studied wood species showed an increase in the f_c0 value with increasing time of exposure at 60 °C. For E_c0, this phenomenon occurred only for the jatobá tamarindo and cupiúba wood species.

The aim of this study was to evaluate the effect of the moisture loss, diameter, and wood density on the appearance of surface cracks and end splits in Eucalyptus urophylla logs. The drying and emergence of defects were evaluated in 108 logs with diameters ranging from 60 mm to 150 mm from the initial moisture content to the equilibrium moisture content. The defects were measured during this time. Smaller diameter logs dried faster than larger diameter logs and took less time to reach the fiber saturation point. Surface cracks tended to develop during the loss of bound water. End splits developed during free water loss and continued to appear during bound water loss. Smaller diameters presented higher percentages of surface cracks compared with larger diameters, while larger diameters had a tendency for higher percentages of end splits compared with smaller diameters. The density did not influence the total emergence of end splits, but it did influence the total emergence of surface cracks, indicating a possibility for the selection of genetic material with lower tendency for cracking. Overall, the results reinforce the need to control drying at its beginning in order to decrease the risk of defects.

As a renewable agricultural solid waste, Camellia oleifera nut shell (CONS) is often discarded or burned, causing adverse environmental impact and a waste of resources. The purpose of this work was to develop a CONS-based bioadsorbent for the removal of heavy metals. Both CONS and ethanol/NaOH-modified CONS (MCONS) were prepared. The specimens were characterized using physiochemical composition, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX). The effects of pH, initial metal concentration, adsorbent dosage, adsorption time, and temperature on the Cr(VI) and Cu(II) removal were evaluated. The adsorption kinetics, isotherms, and thermodynamics were determined. The MCONS sample had a higher carboxyl group content and surface area than the CONS sample, which helped explain its enhanced adsorption performance of heavy metals. The maximum uptake capacity of Cr(VI) and Cu(II) was 16.39 mg/g and 27.26 mg/g for MCONS, compared with 6.34 mg/g and 9.89 mg/g for CONS. The adsorption kinetics for CONS and MCONS fit well with the pseudo-second-order kinetic model. The adsorption isotherms fit well to the Langmuir model. The thermodynamic analyses revealed that the adsorption process was spontaneous and exothermic.

Hemicelluloses contribute to many intrinsic fiber properties, such as the swelling, fibrillation, bonding ability, and hornification tendency. During hornification, additional cross-linking between cellulose fibrils leads to a reduction in the swelling and water-holding capacity of pulp.  The specific surface area, fibrillation, and flexibility of fibers also tend to decrease. To improve the plasticity of fibers and formability of the resulting paper, effective ways to control the fiber properties and their interactions in paper are highly desirable. This work investigated the role of xylan in the plasticization of bleached birch pulp fibers, as hemicelluloses act as natural spacers and thus reduce the interfibrillar cross-linking. Controlled removal of hemicellulose from fiber cell walls was performed using alkaline extraction and enzymes. The results confirmed that the xylan content noticeably influenced fiber shape and sheet properties, such as the tensile strength, strain at break, density, and 2D formability.  A 60% reduction in xylose content reduced the tensile index by approximately 65% and strain at break by 50% compared to the original sample. The reductions were proportional to the amount of xylan removed and could be attributed mainly to the reduced interfibre bonding.