Wood and Fiber Science (E-Journal)
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Impregnation of Scots Pine with Compound Modifier and Induction of In-Situ Polymerization by Heating
Get PDFRecently, Scots pine wood has received tremendous attention in China because of its highstrength weight ratio and aesthetic grain pattern.However, there are some disadvantages for Scots pinesuch as its low density, inferior mechanical strength, and low dimensional stability. In the presentresearch, Scots pine has been impregnation by pulse dipping at 0.7-0.8 MPa for 150 minutes with ureaformaldehydeprepolymer, 1,3-dimethylol-4,5-dihydroxyethyleneurea and sodium silicate sol, and thesodium silicate sol has been cured within the wood micropores by in situ gel polymerization by kilndrying, so that a Si-O-Si framework can be deposited inside the wood structure. The mechanical propertiesand dimensional stability of the modified wood were investigated, and the water absorption decreasedfrom 121.13% to 59.13%. The Fouriertransform infrared spectroscopy showed the chemical changes inwood after modification and illustrated the modified mechanism. The thermogravimetric analyzer showedthat the thermal stability of modified wood improved. Finally, scanning electron microscopy and energydispersive analysis of X-rays micrographs proved that the good interfacial adhesion of modifier betweenwood fiber and polymer.
Qualitative Analysis of the Extractives of Orange Wood
Get PDFOrange production is the third largest agricultural activity in São Paulo state, Brazil but, unfortunately, the orange orchards there have been facing phytossanitary problems. As a result, orchards are being eradicated by burning which may not be the most appropriate way of dealing with this potentially useful biomass. A better approach might be to extract the valuable chemicals from the orange wood, but little information exists on the nature of the extractive components and their chemical potential. Accordingly, the aim of this study was to determine the qualitative chemical composition of orange wood extractives. Four solvent systems were examined in this work (acetone, ethanol:toluene [1:2], dichloromethane and water at three different temperatures), and 221 different chemical components were extracted, and 33 components were identified in the extracts using gas chromatography coupled with mass spectrometry. The ethanol:toluene system extracted the most compounds (48.5% of the total) and the dichloromethane extracted the least (16.3% of the total). Based on a literature review of potential applications, 79% of the identified chemical components in the extractives have potential use in the chemical, pharmaceutical and/or food processing area. This is important information for the future of orange wood utilization and warrants further studies related to the quantitative analysis of the compounds
CHEMICAL CONSTITUENT DISTRIBUTION WITHIN MULTILAYERED CELL WALLS OF MOSO BAMBOO FIBER TESTED BY CONFOCAL RAMAN MICROSCOPY
Get PDFThe distribution of cellulose and lignin is key to its physical and mechanical properties of woody materials. This study was carried out to investigate chemical constituent distributrion distribution of Moso bamboo (Phyllostachys pubescens) fiber using confocal Raman microscopy (CRM) with a particular focus on its unique multilayered structure. The results showed that syringyl and guaiacyl units of lignin were widely distributed across the whole cell wall, including the cell corner (CC) and compound middle lamella (CML), whereas p-hydroxyphenyl units were mainly located in CC and CML regions. A series of CRM images of Bbamboo fibewr cell walls confirmed that different concentration of specific chemicals were present in the multilayered structure. Lignin concentration did not always declined from the periphery to the central part but sometimes increased close to lumen edges as well as some layers. Furthermore, variation of lignin and cellulose concentration across cell wall could be obtained by using the line scanning function. Distribution difference of lignin and cellulose was generally located in CML and lumen side as well as some borders between two adjacent secondary layers. The results from this study will deepen the understanding of the organization of Moso bamboo cell walls
CHEMICAL FORCE MICROSCOPY ANALYSIS OF WOOD-PLASTIC COMPOSITES PRODUCED FROM DIFFERENT WOOD SPECIES AND COMPATIBILIZERS
Get PDFAlien invasive species are posing a serious and direct threat to biodiversity, water security, and productive use of land in South Africa. Most of these species need to be cleared and are therefore regarded as waste material, which could become raw material for wood-plastic composites (WPCs). WPCs containing wood from Pinus radiata, Eucalyptus grandis, Acacia mearnsii, Acacia longifolia, Acacia saligna, and Casuarina cunninghamiana trees, low-density polyethylene (LDPE) and three different compatibilizers: namely the commercially available ethylene vinyl alcohol (EVOH), polyethylene graft-maleic anhydride (PE-g-MA), and thermally degraded LDPE (dPE)—were studied. The determined properties included MC, density, tensile strength, and adhesive forces between the wood and compatibilizer components. The adhesive forces were determined using chemical force microscopy with functionalized, coated tips. WPC samples were compounded and injection molded. EVOH as compatibilizer proved to be very sensitive to the wood species incorporated into the WPC blend. Composites containing PE-g-MA and dPE as compatibilizer had a higher tensile strength for all the wood species. Composites containing dPE as compatibilizer showed less variation in all samples for tensile strength and adhesive force measurements. The densities and tensile strengths of the samples compares well with some commercial WPCs. The study shows that the inexpensive dPE outperforms commercially available compatibilizers and effectively promotes adhesion in WPCs. It was also shown that the studied invasive wood species can be incorporated into WPCs, if the correct compatibilizer is chosen. The differences in the results of the study seem difficult to relate due to the many factors such as the wood species, MC, density, compatibilizers, and processing method. However, the micro properties can give enough information regarding the macro properties of WPCs.
RADIAL VARIATION OF DENSITY AND ANATOMICAL FEATURES OF EUCALYPTUS NITENS TREES
Get PDFThis paper studies the relationship between apparent density and some anatomical properties of Eucalyptus nitens such as vessel frequency, vessel area, ring width, fiber cell wall thicknesses, and fiber length. The study involved 29 trees from 10 families of Eucalyptus nitens cut from a 17-yr-old plantation in Southern Chile. The properties were determined along the radial direction of the trees by using X-ray equipment and at selected positions through microscope and fiber quality analyzer equipment. The results showed that the anatomical properties of E. nitens did not change gradually from pith to bark, but they were better described by dividing the tree radius into three different wood-zones referred as inner-, middle-, and outer-wood. The apparent density of E. nitens was dependent of the vessel area, cell wall area, ring width, and latewood width. The correlation coefficient between apparent density and vessels area was negative and the correlation coefficient between apparent density and cell wall area, latewood ring width, and total ring width were positive. These means that E. nitens wood with lower density tended to have higher vessel area, and lower fiber cell wall area, ring width, and latewood width.
RELATIONSHIP BETWEEN LOBLOLLY PINE SMALL CLEAR SPECIMENS AND DIMENSION LUMBER TESTED IN STATIC BENDING
Get PDFPrior to the 1980s the allowable stresses for lumber in North America were derived from testing of small clear specimens but the procedures changed because these models were found to be inaccurate. Nevertheless, small clear testing continues to be used around the world for allowable stress determinations and in studies that examine forest management impacts on wood quality. Using small clears and nondestructive technologies is advantageous because of the ease of obtaining and testing small clear specimens compared to lumber. The objective of this study was to compare the mechanical properties in bending of small clear specimens with lumber specimens for loblolly pine. Eight hundred and forty-one pieces of lumber in the No. 1 to No. 3 grades and 2×4 to 2×10 sizes were collected from a forest-thru-mill study and tested in static bending. A small clear specimen (25 x 25 x 410 mm) was prepared from each piece of lumber and tested in static bending. The effect of growth ring orientation was explored and overall samples tested on the radial or rift face did a better job of explaining the variation in lumber than samples tested on the tangential face; however, the relationships were generally poor for the modulus of elasticity (MOE) (R2 = 0.22) and modulus of rupture (MOR) (R2 = 0.11) pooled data. A lumber-based multiple regression model explained 44% and 37% of the variability for MOE and MOR, respectively; whereas a stand-based multiple regression model explained 41% and 29% of the variability for MOE and MOR, respectively
MECHANICAL BEHAVIOR OF HYDROTHERMALLY TREATED OIL PALM WOOD IN DIFFERENT BUFFERED PH MEDIA
Get PDFThis study was carried out to determine mechanical properties of oil palm (Elaeis Guineensis) wood (OPW) in different buffered pH media; alkaline (pH 8), acidic (pH 5) and water at a temperature of 140 ºC for 120 min. The OPW samples were taken from outer part of trees. The modulus of rupture (MOR), modulus of elasticity (MOE), the compression strength parallel to grain (PCII) and hardness strength (HB) were measured on treated and untreated samples. The different buffer media significantly affect the mechanical properties of OPW. The results of MOE, MOR, PCII and HB of treated specimens showed a significant decrease compared to untreated specimens. The PCII and HB properties were significantly different between treated samples in water and pH 5 with the treated samples in pH 8 and also untreated samples. It was concluded that the hydrothermal treatment in the buffered medium decreased significantly the mechanical properties of treated specimens of OPW that could be related to the degradation of hemicelluloses. This highly affects bending and tensile strengths of the OPW
Effect of Extreme pH on Bond Durability of Selected Structural Wood Adhesives
Get PDFThis is the second part of a two-part study aimed at examining the effect of extreme adhesive pH on bond durability. The first part dealt with short-term exposure and this second part dealt with long-term exposure. This part also included an examination of wood degradation by adhesive pH.Nine structural wood adhesives [four high pH phenol formaldehyde (PF), one intermediate pH phenol-resorcinol formaldehyde (PRF), two low pH melamine formaldehyde (MF), and two low pH melamine-urea formaldehyde (MUF)] were studied in terms of their pH effect on wood-adhesive bond durability using Douglas-fir wood substrate with specimens tested in block shear. The block shear specimens were initially subjected to vacuum-pressure treatment under water, followed by exposure, while wet, at 50°C for 0, 4, 8, 12, and 17 months. At each exposure period, the specimens were dried to their original moisture content prior to testing for shear strength and evaluation of wood failure.Indications of the extent of degradation of the wood layer adjacent to the bond line due to adhesive pH during the long-term exposure were also examined by the 1% sodium hydroxide solubility test. There were indications that the wood layer closest to the bond line, which contained included glue, had higher solubility compared to those farther from the bond line. This suggests that wood degradation and/or adhesive decomposition occurred and was considered to be induced by the adhesive alkalinity or acidity under the long-term exposure conditions.The PF showed the best durability performance followed, in decreasing order, by PRF and MF/MUF. The latter adhesives degraded completely after an exposure period of 8 to 17 months.The four PF adhesives passed the shear strength and wood failure requirements of the well-known North American structural wood adhesive standards indicating that their high pH had no significant detrimental effect on the wood-adhesive bond durability after the 17-month exposure period despite their being subjected to multiple cyclic tests. This observation was not apparent for the PRF, and the pH effect was considered inconclusive for the MF/MUF since they degraded during the exposure period.The results of this study provide support to wood adhesive standards that do not impose restriction on the upper spectrum of the pH range, and would be useful to adhesive standard developers. These results also serve as background information for adhesive companies in their formulation of wood adhesives as well as for bonded wood product manufacturers in their use of adhesives and for builders in their use of bonded wood products
LIFE CYCLE IMPACTS OF NORTH AMERICAN WOOD PANEL MANUFACTURING
Get PDFAbstract. Manufacturing building products such as wood panels has environmental impacts, including contributions to climate change. This paper is a compilation of four studies quantifying these impacts using the life-cycle assessment (LCA) method on five wood-based panel products made in North America during 2012. LCA is an internationally accepted and standardized method for evaluating the environmental impacts of products. Using LCA, holistic environmental impacts were calculated based on survey data from mills on emissions to air and water, solid waste, energy consumption, and resource use. The present study incorporated cradle-to-gate production of nonwood materials including additives and energy products, such as natural gas and coal, consumed at the production facilities. In addition, primary transport of wood materials to the production facilities was included. These primary data were entered in LCA modeling software on a production unit of 1 m3 of the panel to estimate manufacturing gate-to-gate life-cycle inventory (LCI) flows and major environmental impacts. The LCI flows and environmental impacts were converted to a functional unit of 1 m2 of the wood panel (i.e., final product) produced. The following products were evaluated with their stated panel thicknesses in millimeters: oriented strandboard (9.5), southeast (SE) and Pacific Northwest (PNW) softwood plywood (9.5), cellulosic fiberboard (12.7), and hardboard (3.2). Results are provided here on cumulative primary energy consumption and global warming impacts. Cumulative primary energy consumption was 74.0, 73.5 (SE), 68.7 (PNW), 76.0, and 88.3 MJ/m2, with biomass energy percentage of 50%, 50% (SE), 64% (PNW), 12%, and 47 %, respectively. Global warming impact was 1.97, 1.90 (SE), 1.23 (PNW), 3.91, and 2.47 kg CO2-equivalent/m2, respectively. The panel products evaluated here are mostly not interchangeable, thus results for the panel products should not be compared. Using woody biomass energy for panel production reduces their impact on climate change
MICRO X-RAY COMPUTED TOMOGRAPHY OF ADHESIVE BONDS IN WOOD
Get PDFMicro X-ray computed tomography (XCT) is an emerging technology that has found many applications in biology and the study of materials. Synchrotron-based micro computed tomography has been adopted for the study of adhesive bonding in wood. This paper reviews recent developments of an integrated project that uses micro XCT to assist with modeling of adhesive bonds and to assess the role of cell wall penetration on moisture resistance. The research includes study of: anatomical features of several commercially important wood species, penetration of three adhesive types into wood, moisture effects on bonding, and mechanical performance of bonds during XCT scanning