Wood and Fiber Science (E-Journal)
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EFFECTS OF COMPATIBILIZERS ON SELECTED PROPERTIES OF HDPE COMPOSITES HIGHLY FILLED WITH BAMBOO FLOUR
Full text linkIn this study, maleic anhydride–grafted high-density polyethylene (HDPE-g-MAH) and glycidyl methacrylate–grafted high-density polyethylene (HDPE-g-GMA) were synthesized by melting grafting reaction using styrene as a comonomer. These two functionalized HDPEs and three commercial functionalized polyolefins (Fusabond®M603, PE-g-MAH, and PEW-g-MAH) were used to compatibilize HDPE/bamboo flour (BF) composites. The morphologies and properties of compatibilized and uncompatibilized composites were compared to determine the optimal compatibilizer for HDPE/BF composites. Besides, the effect of HDPE-g-MAH and HDPE-g-GMA contents on the properties of HDPE/BF composites was also investigated. The results show that HDPE-g-MAH and HDPE-g-GMA can more effectively improve the mechanical properties of HDPE/BF composites than the three commercial compatibilizers (Fusabond®M603 resin, PE-g-MAH, and PEW-g-MAH). In addition, HDPE-g-MAH is more effective than HDPE-g-GMA because of the stronger interaction between anhydride and hydroxyl groups than that between epoxy and hydroxyl groups. The use of HDPE-g-MAH and HDPE-g-GMA contributes to improve the thermal stability and reduce the water absorption of HDPE/BF composites.
WEAR BEHAVIOR OF DRILL BITS IN WOOD DRILLING RESISTANCE MEASUREMENTS
Full text linkThe objectives of this study were to investigate the wear behavior of drill bits in wood drilling resistance measurements and to understand how the blunting of the cutting edges may affect the cutting forces and ultimately the measurement results. Laboratory resistance drilling experiments were conducted using an IML-RESI PD 400 tool (IML Instrumenta Mechanik Labor GmbH, Wiesloch, Germany) and a standard spade-type drill bit. Results were based on 375 drillings made on a 2.58 m long, freshly cut, defect-free yellow birch (Betula alleghaniensis) log with an average MC of 55.5%, an average density of 710 kg/m3, and a total cutting path length (CPL) of 5011 m. With the use of the photographic facilities of the microscope, wear and blunting parameters such as clearance and rake face wear, cutting edge rounding, wear along the bisecting line of the wedge (sharpness) angle, residual microclearance angle, wear area, and drill bit diameter were measured and calculated for initial condition of the drill bit and the conditions at incremental cutting path lengths. The initial geometry parameters of the cutting head of the drill bit had a big impact on tool wear and blunting, which affected the precision of wood density evaluation. Intensive blunting and wear of the cutting edges occurred on the clearance faces and increased proportionally with the total cutting path length. Rounding of the cutting edges and drilling resistance (torque) were relatively constant within the experimental conditions, indicating that resistance drilling measurement in wood was still accurate as the total CPL reached 5011 m (or 375 drillings). Feeding force was found to be affected by the blunting of the cutting tool and may be used to predict the service life of a drill bit
Wood Variability in Mature Longleaf Pine: Differences Related to Cardinal Direction for a Softwood in a Humid Subtropical Climate
Full text linkMature longleaf pine (Pinus palustris Mill.) trees were harvested to compare wood property data for opposing bark-to-pith wood strips representing the northern and southern cardinal (or compass) directions. For each of the ten 70-yr-old trees used in the study,wood property datawere compared at breast height (BH) and three relative heights: one-quarter height (1Q), midheight (MID), and three-quarter height (3Q). Scanning of the specimens by X-ray densitometry gave specific gravity (SG) profiles that were used to determine wood properties for comparison. No significant differences were determined for wood property data at BH, MID, or 3Q. However, data at 1Q showed higher ring SG (p . 0.043) and percent latewood (p . 0.018) for the northern side, although no differences were observed in the earlywood or latewood SG. This indicated that the higher ring SG for the northern direction results from a greater proportion of latewood. Partitioning the data into estimated juvenile-transition wood and mature wood zones demonstrated that the greater ring SGand percent latewood values in the northern direction occurredwithin the mature wood zone. Findings presented herein appear to provide the first demonstration of variation in wood properties with respect to cardinal direction for a pine species growing in a humid subtropical climate.
The Effect of Culm Age, Height, Node and Adhesive on the Properties of Bamboo Oriented Strand Boards
Full text linkThe effects of native character on the properties of strands board made from bamboo were evaluated, and the effect of mixing adhesive usage on durability property of the board was experientially researched. The strands of bamboo were classified under different bamboo age, height, and node or internode. The sorted strands were manually formed into strand mats and hot-pressed into strand boards using consistent parameters. Analysis of variance was used to analyze the significance of factors. The results of this study indicated that bamboo age was an insignificant factor for both MOR, MOE, and thickness swelling (TS), but significant for internal bond (IB) strength. The bamboo height and nodes in the core layer were a significant factor for parallel MOR, parallel MOE, and IB, whereas two factors had minimal effect on TS. Phenol-formaldehyde resin (PF)/emulsion polymer isocyanate adhesive (MDI) mixed-adhesive bonded board (type 6 PF/ MDI) had less TS and higher MOE retention than MDI only bonded board (type 6) when strand boards were subjected to boiling treatments. This proved that it was more durable, and could be considered as a potentially suitable raw material for moisture/heat–resistant panel for these specific applications
Technical Note: A PRELIMINARY STUDY TO QUANTIFY THE ENVIRONMENTAL IMPACTS OF CONCRETE AND CORK FLOORING
Full text linkCross-laminated timber (CLT) is currently sought as a sustainable and green building material. It does not meet the International Building Code sound insulating requirements, and either a concrete slab or hardwood flooring is needed to meet the acoustic and vibrational performance benchmark. Cork, the bark of the cork oak, is well known for its sound insulating properties and often used for flooring applications in Europe. The cork-based flooring system is a potential solution to the acoustic problem faced by the CLT building industry. The goal of this preliminary study was to quantify the environmental impacts of a concrete and a cork-based flooring system that includes CLT. A life-cycle analysis (LCA) is conducted to focus on a cradle-to-gate comparison of a cork flooring system with a locally sourced concrete flooring system for use in a proposed CLT structure in Portland, OR. The LCA reveals that the global warming potential (GWP) of concrete is 25% higher for the concrete flooring system. For cork flooring, the GWP is mainly driven by inorganic compounds in the flooring assembly. The main source for cork is Portugal, which increases the GWP of the cork flooring system, in contrast to that of concrete flooring, which typically has a regional production and supply system. As environmental abatement costs increase, the profitability of cork flooring can increase to justify the creation of an appropriate system to close the loop.
FABRICATION AND CHARACTERIZATION OF NANO-FE/WOODCERAMIC COMPOSITES
Full text linkFuran resin added with γ-Fe2O3 nanoparticles and Chinese fir sawdust were mixed and compressed into boards. The boards were then sintered in a vacuum furnace to obtain a nano-Fe/ woodceramic composite. The phase constitution, microstructure, and element distribution of the composite were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy disperse spectroscopy (EDS), respectively. The mechanical properties, volume electrical resistivity, and wave adsorption properties were investigated. XRD analysis indicates that α-Fe, Fe3C, and graphite carbon exist in the nano-Fe/woodceramic composite, and α-Fe promotes the graphite degree of woodceramic. SEM and EDS observations indicate that the composite has a porous structure and α-Fe nanoparticles distributed in the woodceramic. Experimental results show that the maximum values of bending strength and compressive strength are 11.74 MPa and 13.86 MPa, respectively. The minimum value of volume electrical resistivity is 0.021 Ω$cm. The minimum reflection loss value is11.45 dB at 9.68 GHz with 3mm thickness of absorbing layer.
Breakeven Point in Ultimate Thickness Between Moisture-Reduced Shrinkage and Thickness Recovery of Densified Softwood Species: Part 1: At Room Temperature
Full text link Thermo-hygro-mechanical (THM) densification technique has been used to increase the density and mechanical properties of underutilized softwoods. One potential application of the densified softwoods is the substitute of hardwood flooring. This technique is usually employed to mechanically compress the softened wood in the radial direction with the assistance of a high temperature greater than 100°C. Use of high temperature shows that the THM densification process consumes a lot of thermal energy, losing the economic competitivity in comparison with the hardwood floorings. From the energysaving point of view, the authors tried to densify two softwood species at three temperatures of 20°C, 50°C, and 90°C with various compression ratios (CRs), followed by air-drying (AD) the densified wood specimens at room temperature. It was discovered that the decrease of MC would result, during the AD conditioning, in shrinkage of densified wood, which could offset part of the thickness recovery of densified wood. However, this phenomenon was not well addressed. This study was aimed at discussing the effect of shrinkage on the thickness recovery ratio (TRR) of densified softwoods. To ignore the influence of temperature on the shrinkage capability of wood because of the decomposition of hemicellulose, only the data of densified wood specimens compressed and posttreated at room temperature were analyzed in this study. Two softwood species used were eastern white pine (Pinus strobus) and balsam fir (Abies balsamea). The CRs ranged from 0.05 CR and 0.65 CR. The major findings were: 1) the final thickness of densified wood was a result of “recovery” containing elastic deformation and viscoelastic deformation, and “shrinkage” of cell walls; 2) the relationship of TRR of densified pine or fir and CR followed an exponential increase trend at 20°C; 3) after AD conditioning, the breakeven point in thickness between moisture-reduced shrinkage and visco-elastic recovery when the CRs of densified pine and fir at 20°C were 0.12 and 0.13, respectively
LATERAL LOADS OF STAPLED-GLUED SURFACE-TO-SURFACE JOINTS IN ORIENTED STRANDBOARD FOR FURNITURE
Full text linkThe additive effects of the number of staples and gluing on ultimate lateral resistance loads of surface-to-surface, multistaple- and glue-connected joints in oriented strandboards (OSB) were investigated. Experimental results indicated that for a stapled–glued OSB joint with a given configuration of surface-tosurface bonding area of two joint members, its ultimate lateral resistance load and stiffness are governed by the number of staples used and gluing, respectively. Applying glue to multistaple-connected OSB joints can alter the effect of the number of staples used on their ultimate lateral resistance loads. Gluing increases joint lateral resistance loads, but this increase will not be significant when the number of staples used reaches a critical number. Applying glue to a stapled OSB joint improves its stiffness when compared with the stiffness of a stapled-only joint. The differences in ultimate lateral resistance loads of stapled–glued joints among three OSB materials evaluated in this study were not significant when the number of staples was six or less, and the differences became significant when the number of staples increased to eight.
TECHNICAL NOTE: EFFECT OF FIRE RETARDANT TREATMENT ON MECHANICAL PROPERTIES OF MEDIUM-DENSITY COIR COMPOSITE BOARDS
Full text linkComposite boards manufactured from natural fibers such as coir can be a useful substitute for wood and plywood. They can also be chemically treated to improve its fire-resistant capabilities. To be rendered useful as a construction material, the chemical treatment has to impart fire resistance without affecting its structural properties. This article investigates the effect of fire-retardant (FR) treatment on mechanical and physical properties of medium-density coir fiberboards when treated with a waterborne solution containing boron compounds using the method of hot and cold bath treatment. Physical properties such as density, MC, and thermal conductivity were determined to compare the performance of treated samples against untreated samples. Investigation of mechanical properties such as tensile strength, bending strength, tensile modulus, and flexural modulus were also carried out using a combination of tensile, bending, and compression tests. The results obtained were encouraging, and it was observed that the coir fiberboards after FR treatment retained much of their properties and in many cases, even improved marginally.