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- 1. The family of wood composite materials Maloney, T M . Forest Products Journal ; Madison Vol. 46, Ed. 2, (Feb 1996): 18. Link para o documento do ProQuest RESUMO Wood composites are defined as materials that have the commonality of being glued or bonded together. A certain group of composites are now being grouped together and described as engineered wood products. A description is given for panel products, including: 1. softwood plywood, 2. blockboard, 3. hardwood plywood, 4. particleboard, 5. medium density fiberboard, 6. insulating board, 7. hardboard, 8. Com-Ply panels, 9. oriented strandboard, and 10. waferboard. The history of molded products, inorganic-bonded products, and lumber and timber products is presented. TEXTO COMPLETO Millions of tons of wood composites are now manufactured annually from previously unused species as well as forest and mill residues (and agricultural residues). The development of these wood composites has occurred mostly over the past 40 years. It is a revolution in the forest products industry, albeit a "silent revolution" not recognized by the general public. The term "wood composites" is relatively new. The forest products industry has struggled to properly name the many different materials that have been developed by gluing small particles or other elements into larger materials. In this discussion, composites are defined as materials that have the commonality of being glued or bonded together. This description covers a multitude of products and it is used to avoid the use of trade names that may confuse people. Most of today's wood composites are of relatively recent origin, within the past 40 years. Composites include not only panels, but also molded products, lumber, large timbers, components, and products made with combinations of wood and other materials (e.g., plastic fiber or straw). Composites utilize what was previously waste wood residue or little used or noncommercial species. Even agricultural residues can be used. Very little raw material is wasted in the manufacture of composites. Wood is a very energy efficient raw material. Almost half of the industrial materials manufactured in the United States are wood products; however, only about 4 percent of the total energy needed to manufacture all industrial materials is used by the forest products industry. Wood composites efficiently use this energy-conserving renewable resource. THE FAMILY OF ... WOOD COMPOSITES... The term "composite" seems to be the most appropriate to describe any wood material made of smaller pieces and glued together. Some composite materials found in today's world are panels, molded products, inorganic-bonded products, and lumber or timber products. This composite family is shown on page 20. This family can be expanded easily to include all types of laminated materials (from overlaid panels to laminated beams), edge-glued panels, components (I-beams, T-beam panels, stress-skin panels), and perhaps in the future even to large molded building parts or even buildings. A certain group of composites are now being grouped together and described as engineered wood products (EWP), for example, plywood, variations of structural panels, and glued laminated timber. Other composites such as particleboard and medium density fiberboard (MDF) have also recently been described as engineered wood PDF GERADO POR SEARCH.PROQUEST.COM Page 1 of 9
- 2. products. Almost all of the composites can be engineered to various specifications, thus taking full advantage of wood's inherent properties while at the same time improving upon these properties through materials science and technology. Also, almost all of these composites can be used structurally. For some reason, recent publications have called particleboard and MDF "nonstructural." This is untrue. These materials are being used in North America and elsewhere in the world as structural panels in building. They are approved for structural use by various building codes and government agencies. Even low density insulating board is approved for structural use. ... PANEL PRODUCTS... SOFTWOOD PLYWOOD... Softwood plywood has dominated the North American structural panel market for many years. However, oriented strandboard (OSB) now claims a very high proportion of this market because it usually is a lower cost product to manufacture. Significant improvements in plywood manufacturing have resulted in reduced production costs, which has enabled the softwood plywood industry to increase production and remain competitive with OSB. In the past few years, however, a reduced timber supply in the western United States as well as increases in veneer log prices have caused a considerable number of plants to close. Plywood plants are now, for the most part, attempting to produce mostly higher value products rather than sheathing, subfloor, and other basic building panels, leaving much of the sheathing market to the lower cost OSB. Softwood plywood manufacture has undergone a dramatic change in recent years. Some examples of the manufacturing changes include pretreatment of the veneer blocks, which has enhanced veneer quality and the amount of veneer produced; computerized X-Y peeler block chargers; ultrasonic veneer block scanning; powered nose bars; and linear-positioned lathe knife carriages, which have become part of the conventional lathe and further increase the amount of veneer produced. Also, new lathes have been introduced that can peel blocks to cores of less than 2 inches in diameter. Changes in the gluing system, such as gluing higher moisture content veneer and foaming the glue, have reduced the amount of adhesive required and, hence, have lowered production costs. A major breakthrough is the development of phenolic glues for use with veneers at moisture contents of 10 percent or more instead of 3 or 4 percent. This has resulted in higher dryer productivity, improved press productivity, lowered glue spreads, better pre-pressing, better assembly time tolerance, improved veneer gluability, and fewer panel blows. Some plants have obtained up to a 20 percent savings in glue cost, while simultaneously saving on dryer and press costs. Gluing veneer with a high moisture content (up to 15 percent) results in a product closer to the equilibrium value in actual use, thus reducing warp and dimensional changes. However, a plant must operate under strict process controls to be successful in gluing high moisture content veneer, otherwise product quality will be reduced significantly. HARDWOOD PLYWOOD... Unlike softwood plywood, which is used mostly for structural applications, hardwood plywood is used both structurally and also as decorative panels. This is a product that can be traced back to ancient times. Today, in the United States, hardwood plywood includes hardwood veneer applied over other substrate materials such as particleboard. A number of developments have taken place over the years that enable a plant to recover more veneer from a given log and to produce quality plywood more efficiently. The newer versions of lengthwise veneer slicers have been installed in many plants, particularly in East Asia, Australia, and now in North America. These slicers do not have the output of conventional slicers, but they work well in smaller plants. They allow the recovery of difficult-to- process wood in conventional operations and allow sawmills to produce veneer from quality wood material. Thus, sawmills have the opportunity for a value-added product by producing veneer as well as lumber. Some of the reasons for using lengthwise slicers include low investment, no foundation requirements, low energy consumption, complete, or near complete, utilization of the flitches, automatic operation, and the ability to produce PDF GERADO POR SEARCH.PROQUEST.COM Page 2 of 9
- 3. thin veneer with high-quality surfaces as well as thick veneer. The combination of a sawmill and veneer mill has resulted in significantly increased product recovery and profit. A major competitor to hardwood plywood is thin MDF. With appropriate high-quality overlays or prints, thin MDF appears the same as hardwood plywood. This product has captured significant amounts of the hardwood plywood market. BLOCKBOARD... Blockboard is often overlooked today, but its old technology, or variations on the old technology, could provide panel-building products in many places. Conventional blockboard panels have been made with strips of lumber in the core with crossbands of veneer or hardboard faces. A newer version is produced by glue edge jointing the core lumber strips and using thin lumber faces rather than veneer. The adhesive cost can be quite low. About 14 new plants have been built in Europe using this new technology. Blockboard is used for paneling, furniture, and extensively for concrete formwork in Europe. PARTICLEBOARD... Particleboard is a generic term for a panel that is manufactured from lignocellulosic materials (usually wood, primarily in the form of discrete pieces or particles, as distinguished from fibers) combined with a synthetic resin or other suitable binder and then bonded together under heat and pressure in a hot press. The process uses the added binder to create the entire interparticle bond; other materials may be added during manufacture to improve certain properties. Particleboards are further defined by the method of pressing. When the pressure is applied in the direction perpendicular to the faces, as in a conventional multi-platen hot press, they are defined as flat-platen pressed; and when the applied pressure is parallel to the faces, they are defined as extruded. Particleboard remains the world's dominant furniture panel, although considerable amounts of its production also go into structural applications such as manufactured home floors, roof sheathing, wall panels, stair treads, and for house floors elsewhere in the world. The first platen-pressed particleboard plant started operation in Dubuque, Iowa, in 1933. This small plant ran until 1942. A larger commercial plant commenced operation in Germany in 1941. The great increase in particleboard production started in the 1950s. Extruded particleboard was developed in Germany in 1947-49. A similar process was developed in the United States. Numerous plants were built throughout the world including the United States. However, low production capacities and some board physical property limitations kept extruded particleboard from becoming a major product line. The basic raw materials for particleboard are plant residues or low-quality logs. Planer shavings and sawdust are the dominant raw materials in the United States and Canada because of the huge sawmill industry in these countries. Some recycled wood material, where it is economical to use such a substance, is now part of the raw material supply. A new facility that manufactures particleboard from straw just began operation in North Dakota. Bagasse (sugar cane stalks) has been used for board in a few countries. MEDIUM DENSITY FIBERBOARD... MDF is a dry-formed panel product manufactured from lignocellulosic fibers combined with a synthetic resin or other suitable binder. The panels are compressed to a density of 0.50 to 0.80 specific gravity (31 to 50 pcf) in a hot press by a process in which the entire interfiber bond is created by the added binder. Other materials may have been added during manufacture to improve certain properties. It is generally accepted that MDF production started in Deposit, New York, in 1966, but arguments can be made that the first MDF was made in a plant in Oakridge, Oregon, or in a plant in Meridian, Mississippi. Many new MDF plants have been erected recently and many others are in the planning stages. There are now well over 100 plants worldwide. Thin and thick boards are being produced. Thin MDF is usually produced by newer continuous presses, however, most of the newer plants also use these types of presses to produce thicker panels. A wide variety of raw material types can be handled in an MDF plant: pulp chips, planer shavings, plywood trim, and sawdust. Care must be taken to introduce all of these different raw material types into the process line at PDF GERADO POR SEARCH.PROQUEST.COM Page 3 of 9
- 4. appropriate levels to ensure a consistent quality of fiber. Much of the world uses pulp chips to manufacture MDF; however, it is common in the United States and Canada to mostly use the same raw material as for particleboard: planer shavings and sawdust. Other nonwood materials such as bagasse also make excellent MDF. Many new MDF plants are under construction, particularly in Southeast Asia and Indonesia. The technology for producing MDF has improved greatly in recent years. It appears that a mixture of species can be handled better in an MDF plant than in a particleboard plant. However, there are still some problems when there are significant chemical differences between the species, particularly in designing the resin system. Urea- formaldehyde is still the dominant resin used. The interaction between the chemistry of the wood species and the urea-formaldehyde is well known. Control of the species chemistry is needed to ensure that quality MDF is produced consistently. MDF lends itself well as a substitute for clear lumber. It does not have a grain structure, but finishes and overlays can be used effectively to provide an MDF product that, in appearance, looks like wood. A considerable amount is now used for moldings or millwork, replacing solid wood. INSULATING BOARD (NON-COMPRESSED FIBERBOARD)... Insulating board development started in 1914 in Minnesota, but its manufacture has been slowly decreasing. This is a wet-process system where great amounts of water are used in the process, somewhat like in the manufacture of pulp and paper. The need to clean the water effluent has been a major problem and competition from foamed plastic panels has been a further factor in the decline of insulating board manufacture. Many surviving plants use mineral fiber rather than wood fiber in order to make products that are resistant to fire. One insulating board product still enjoying great success in the United States is Homosote. This product is made of waste newspaper and groundwood paper publications waste. Manufacture started in 1916 (based on technology from Agasote Millboard in the United Kingdom). Homosote is a structural product based on recycled wood fiber. Besides various panels, components for walls and roofs are produced, which combine the board with rigid urethane foams, foils, fiberglass, and other materials. HARDBOARD (COMPRESSED FIBERBOARD)... Hardboard is a generic term for a panel manufactured primarily from interfelted lignocellulosic fibers (usually wood) and consolidated under heat and pressure in a hot press to a density of 31 pcf or greater; other materials such as resin may be added during manufacture to improve certain board properties. Wet-process hardboard uses large amounts of water in the processing, similar to the manufacture of insulating board. This hardboard continues to be an important panel product worldwide. Like insulating board, there are questions about cleaning the waste water. Stricter environmental regulations have eliminated some previous uses of waste water, such as for irrigation. Research on enzymes and bacteria that may clean the water is being conducted and may provide some important developments for wet-process hardboard. Siding has been a major market for wet-process hardboard in the United States, but the development of OSB siding has increased competition in this market. Wet-process hardboard is also being used as a substitute for solid wood in trim applications. Expansion of product lines has included roof covering material in the form of tiles or simulated wood shingles or shakes; this material is untreated and is being manufactured and used in South Africa and the United States. Dry-process hardboard is now becoming quite confused with thin MDF because the processes used for each are somewhat similar. However, usually dry-process hardboard is of higher density than thin MDF. The dry-process hardboard is bound together with synthetic adhesives the same as particleboard and MDF. The board usually has poorer properties under wet conditions than does wet-process hardboard because the hemicelluloses, with their affinity for water, are retained in the furnish rather than partially washed away as in wet-process hardboard. However, a significant development of dry-process hardboard technology (some would argue this is MDF) is the production of door skins. This development will be discussed under molded products; it is a major product line in the United States. COM-PLY(R)PANELS... PDF GERADO POR SEARCH.PROQUEST.COM Page 4 of 9
- 5. COM-PLY panels are made with veneer and particles/flakes. Three-layer panels have veneer faces and particle cores while five-layer panels have a veneer core (laid up with its grain direction at 90 degrees to the face veneer grain direction). Panel-producing plants commenced production in the mid-1970s; however, all but one are no longer operating. Today, one plant in Oregon is producing the five-layer board very successfully for subfloors, sheathing, combination subfloor/floor, and siding. WAFERBOARD... Waferboard was first produced in 1955 in Dover, Idaho, in a plant that closed in the 1970s. The process, invented by James d'A. Clark, uses large flakes, called wafers, that are bonded together into the final panel. The wafers, more or less square in shape, are randomly oriented throughout the panel. Generally made from low-density hardwoods, mostly aspen, waferboard was well accepted in several sheathing applications. The first large production of waferboard occurred in Canada starting in the 1960s. Further production of waferboard in the United States didn't happen until the late 1970s. waferboard has now been replaced in large part by OSB. ORIENTED STRANDBOARD... OSB panels are made from compressed strands lined up (oriented) and arranged in layers (usually three to live) that are oriented more or less at right angles to one another. At times, the core layer may be of random orientation. Panel stiffness and strength approaches that of plywood. OSB came to prominence in the 1980s as the technology developed for manufacturing this product. Almost all of the panels are used in structural applications in the same way as plywood. An exception is the phenolic paper overlaid OSB that is used for siding. OSB is usually thinner compared to waferboard for the same end uses, e.g., 7/16 inch versus 1/2 inch. Thus, there is a material savings when manufacturing OSB. The OSB industry can use small irregular logs as the raw material, but it prefers ones that are relatively straight and about 14 inches in diameter. The reasoning behind this is that usually the logs are debarked with ring-type debarkers. Such debarking with the smaller logs is very time consuming and inefficient. However, a large amount of the logs used are smaller than 14 inches in diameter. Drum debarkers designed especially for smaller-diameter logs are now being used, but then there is some damage to the wood in the debarking operation. There are now over 60 OSB plants in operation, with 20 others expected to begin production before 1998. Almost all of the plants are in the United States and Canada. Other plants in operation or being constructed are in France, Venezuela, Ireland, and Scotland. Great interest in OSB production is being expressed in Southeast Asia. Most OSB is now made with strands that are 3 inches or longer in the surface layers. The core may be of smaller strands and may or may not be oriented. The OSB segment of the industry has become an important part of the structural panel business in recent years, comprising about 30 percent of the structural panel market. This industry was developed using low-density hardwoods such as aspen; however, additional species such as southern pine, lodgepole pine, jack pine, and Scotch pine are now being used. High-density species are still difficult to use because boards produced from such species are also quite high in density. These boards are difficult to handle, cut, and nail, and they are more expensive to ship. ...MOLDED PRODUCTS... Molded products of fiber or particles have a long history in the industry, particularly in western Europe and in the United States. Pallets, table tops, and door casings are some of the molded products made using particles. Molded parts made out of wood fiber and plastic fiber have gained market share in the automobile industry, displacing plastic products. The combination of wood fiber and plastic fiber makes it possible to produce inside car door panels with deep draws or impressions and a high strength-to-weight ratio. These panels are overlaid with various plastic coverings. In recent years, door skins have become an important new molded fiberboard product. Door skins are thin MDF or dry process hardboard panels molded (pressed) into one of many panel door patterns. These skins (one on each side) are then glued to a wood frame to make up the final door. These doors are a replacement for solid wood doors and their manufacture has attracted worldwide interest. Molded structural parts for building offer excellent opportunities in the future. For example, folded plate designs PDF GERADO POR SEARCH.PROQUEST.COM Page 5 of 9
- 6. for use in roof and floor members offer great strength with a minimum use of material. Perhaps molded wood products will find a new life if the cost of plastics continues to increase. ...INORGANIC-BONDED PRODUCTS... Inorganic-bonded panel products are composed of flakes, excelsior (wood wool), fibers, or other small particles that are bonded together with inorganic materials, e.g., Portland cement or gypsum. The first cement-bonded product was made in Austria in 1914 (excelsior bonded with cement). A plant producing this type of material operated in Chewelah, Washington, in the 1930s and 1940s and these products were used for acoustic purposes in many large auditoriums in the Eastern United States. New developments in fast-curing bonding materials and processes have sparked worldwide interest in inorganic- bonded panels. Gypsum fiberboard that utilizes these new technologies has been developed in Germany over the past 20 years and has captured a significant part of the German gypsum board market. Conventional gypsum board has the gypsum between two thick sheets of paper, but this new gypsum fiberboard product has fiber evenly blended throughout the board. The gypsum fiberboard has to be cut and applied differently from the conventional board. The raw material for this product can be all recycled material: waste paper for the fiber and gypsum reclaimed from coal-burning electrical-generating plants. Gypsum fiberboard is being produced in one plant in North America, in Eastern Canada. Roof shingles and shakes are now being produced using wood particles or fibers bonded with cement. Currently, several U.S. plants are making these products. ...LUMBER AND TIMBER PRODUCTS... The decreasing quality of the world's forest and the amount of timber available for producing either conventional lumber or high-quality lumber has led to a tremendous interest in producing composite lumber-like materials. Research has shown that such materials can be made and, indeed, plants are now producing these lumber-like products, which include laminated veneer lumber (LVL), COM-PLY, parallel strand lumber (PSL), and oriented strand lumber (OSL). LAMINATED VENEER LUMBER... LVL has become the most important new lumber construction material. Primarily a structural material, it is made of veneer laid up in one grain direction. It is made in billets 27 to 50 inches wide in either platen or continuous presses. Long press times of over 20 minutes are needed to cure the adhesive in the billets, which are usually 1- 1/2 or 1-3/4 inches thick. Radio-frequency (RF) curing of the gluelines is now being used to significantly reduce the press times. The veneers are nondestructively tested to insure consistent strength in the structural-type LVL. The Trus Joist Corporation (now Trus Joist MacMillan) pioneered the commercial development of LVL starting in the 1960s. There are several LVL plants now operating in the United States. LVL used as flanges in I-joists has garnered about 30 percent of the U.S. wood floor market. LVL products have been used primarily for structural applications, but millwork and furniture also utilize LVL. LVL products mostly use phenolic glues, but new isocyanate and urethane technology is also available. Exposed LVL can be made with colorless glues when desired. It is difficult to tell such products from solid wood. COM-PLY COM-PLY lumber, developed by the USDA Forest Service in the 1970s, is a material composed of random or oriented wood flakes or particles sandwiched between one or more layers of veneer. One or more layers of veneer are placed on the faces or edges of the lumber. A plant for producing COM-PLY lumber was in operation in North Carolina. This plant produced an oriented flakeboard product that was cut into desired widths for making composite lumber. Several layers of veneer were then laminated onto each edge of the flakeboard to make the COM-PLY joist lumber. Veneer was laminated onto the flakeboard faces to make truss lumber. Although this particular plant failed, there is still considerable interest in this product. PARALLEL STRAND LUMBER... ParallamTM is a PSL product developed by MacMillan Bloedel, Ltd., of Canada (now Trus Joist MacMillan). Many PDF GERADO POR SEARCH.PROQUEST.COM Page 6 of 9
- 7. years of research and development led to the pilot plant production of Parallam. PSL products are made of oriented strands of waste softwood veneer or from veneer peeled specifically for the PSL plant. Strand dimensions are about 1R inch wide and up to about 37 inches long. Exterior-type plywood glue is applied to the strands, which are oriented and laid-up into a mat in the lengthwise direction. The mat is then processed through a continuous press. A microwave-type heating system was invented to permit the production of such a thick billet. The billet sizes are generally either 11 by 18 inches or 11 by 14 inches. The billet is sawn into desired lengths, thicknesses, and widths or used as produced. The resulting PSL serves markets where high-strength lumber or timber materials are needed. ScrimberTM is a product developed in Australia. "Scrim" is a term from the textile industry that means loosely woven; "ber" in the name Scrimber comes from timber. For this product, small logs are crushed between rollers, glue is applied, and the oriented mat of material is consolidated in a hot press into lumber. The details of the process are proprietary. The first commercial plant was put into operation in the late 1980s, but it failed. It is now being evaluated for a return to production. The Japanese have developed a similar product called ZephyrwoodTM that is reportedly ready for commercialization. ORIENTED STRAND LUMBER... MacMillan Bloedel, Ltd. developed an OSL lumber product that is now called TimberStrandTM LSL (laminated strand lumber). This is OSL made with nominal 12-inch- (300 mm) long strands. The lumber is pressed in a steam- injection press that produces uniform density throughout. A relatively short press time results from the use of steam-injection pressing. The first manufacturing plant is operated by Trus Joist MacMillan in Minnesota. Other new plants are under construction. OSB manufacturers are interested in this product and some are already producing it. OSB plants are designed so that all the strands in a product can be aligned in one direction, which makes it convenient to produce both OSB and OSL. OSL faces a struggle to enter conventional lumber markets as a common building material because strength properties must be measured and design values assigned to the lumber by testing organizations. This takes considerable time and effort, but this effort is well underway. Railroad ties can be produced by recycling old railroad ties. A product called Cedrite was invented in the 1970s, and was being manufactured in a plant designed to produce 1,600 ties per day. In this process, old ties are chipped; the metal is removed; the chips are hammermilled and then blended with resin in preparation for production. The blended furnish is then placed into metal molds. Hardwood stiffeners are placed in the center of the mats, which measure about 30 inches high, before being compressed to a final thickness of about 7 inches. Once a mat is compressed into a mold, a top plate is secured over the compressed mat. The mold then goes into an oven to cure the resin. ... WHAT'S AHEAD... Much has happened in the field of composites over the last 40 years. Materials are now manufactured in quantities that once were only dreams. It can be estimated that roughly 21 million tons of composite products are manufactured annually in the United States alone, mostly out of previously unusable raw materials. The development of composites has led to a far more efficient use of the trees that are harvested. Machinery and production line developments have resulted in manufacturing efficiencies that further conserve raw materials. In the future, the manufacture of wood composites will increase even more because it is expected that the forest resource will provide fewer larger trees, particularly the conifers preferred for so long in the manufacture of lumber and plywood. Composite products have become a large and important segment of the forest products industry, and even more new composite plants are expected to begin production in the next few years. ...BIBLIOGRAPHY... American Hardboard Association. 1988. Basic hardboard. ANSI/AHA A 135.4. American Hardboard Assoc. Palatine, 111. Food and Agriculture Organization of the United Nations, Secretariat. 1990. World production capacities: plywood, PDF GERADO POR SEARCH.PROQUEST.COM Page 7 of 9
- 8. particleboard, and fibre board. FAO World Survey 1989. FAO Committee on Wood-Based Panel Products. WPP/90/2. FAO, Rome, Italy. Maloney, T.M. 1993. Modern Particleboard 5 Dry-Process Manufacturing. Updated edition. Miller Freeman Publications, San Francisco, Calif. Maloney, T.M., ed. 1967-1995. Proceedings of the International Particleboard/Composite Materials Symposium. 29 volumes. Washington State Univ. Pullman, Wash. Moslemi, A.A., ed. 1988-1994. Proceedings of the Series of Conferences on Inorganic Bonded Wood and Wood Fiber Composite Materials. 4 volumes. University of Idaho, Moscow. Idaho. National Particleboard Association. 1993. Particleboard. ANSI A208.1. NPA, Gaithersburg. Md. National Particleboard Association. 1994. Medium density fiberboard for interior use. ANSI/A 208.2. NPA, Gaithersburg, Md. Suchsland, O. and G. Woodson. 1986. Agriculture Handbook 640. USDA Forst Serv., Washington, D.C. DETALHES Assunto: Wood products; History; Composite materials; Applications Classificação: 8630: Lumber &wood products industries, includes paper Título: The family of wood composite materials Autor: Maloney, T M Título da publicação: Forest Products Journal; Madison Volume: 46 Edição: 2 Páginas: 18 Número de páginas: 9 Ano de publicação: 1996 Data de publicação: Feb 1996 Editora: Forest Products Society Local de publicação: Madison País de publicação: United States, Madison Assunto da publicação: Forests And Forestry--Lumber And Wood, Building And Construction ISSN: 00157473 CODEN: FPJOAB PDF GERADO POR SEARCH.PROQUEST.COM Page 8 of 9
- 9. LINKS: Copyright da base de dados © 2018 ProQuest LLC. Todos os direitos reservados. Termos e condições Entre em contato com o ProQuest Tipo de fonte: Scholarly Journals Idioma de publicação: English Tipo de documento: PERIODICAL Número de registro: 01160796 ID do documento ProQuest: 214632589 URL do documento: https://search.proquest.com/docview/214632589?accountid=146784 Copyright: Copyright Forest Products Society Feb 1996 Última atualização em: 2013-11-07 Base de dados: Technology Collection PDF GERADO POR SEARCH.PROQUEST.COM Page 9 of 9