How Is Engineered Wood Made?
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The Basic Idea
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Engineered wood may be composed of cellulose fiber from wood or it may have little wood in it at all. The original engineered wood was fabricated by the ancient Egyptians who layered veneers of fine wood over common varieties and glued them together under pressure. This process is still used to make plywood. The first engineered woods in the 20th century--Homasote and Masonite--were "fiberboard," made with scrap fiber and glue used as underlayment for floors and primitive insulation. Most engineered woods are manufactured using cellulose fiber and a binding agent, either compressed or extruded using heat or using plastic or cement. Each type of engineered wood, like the first plywood and the early fiberboard, is manufactured for a certain use. New types of material are created to address the weaknesses or deficits of earlier types. Research has created engineered woods that are strong, resist moisture and never need to be painted.
Wood and Glue
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Plywood, glued-laminated lumber (glulam) and particle-based lumber (oriented and laminated strand, waferboard and particleboard) use glues and resins to bond sheets or fragments of wood together. Glulam is simply large pieces of lumber glued together under pressure to make posts and framing members for large buildings. Layers of wood (plywood and veneers) or chips (MDF, OSL, LSL, waferboard and particleboard) are set with glue and pressed or rolled to create hard, heavy composition board suitable for indoor or outdoor use, depending on the glues and binders used. Early glues based on resins tended to break down in outdoor applications, leading to "de-lamination" of plywood and other laminates, prompting scientists to develop acrylic and epoxy-based binders that would stand up to heat, cold and water. Fiberboard, a glue-based composite that uses soaked and mashed fibers from waste lumber, is an even more efficient use of wood; the fiber and glue are poured into long sheets and heat-cured. The resulting material, akin to a hard, strong papier-mache, is widely used in floor underlayment, insulation and other interior uses. The fibers, however, tend to absorb moisture whatever binders are used and are not popular for exterior construction. As with other wood-and-glue products, fiberboard is manufactured in various strengths and hardnesses, based on fiber type and density.
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Wood and Other Materials
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Some engineered woods use plastics or minerals to fabricate materials that can be used like lumber but last much longer. Wood-plastic composites mix fiber and plastic into pellets, then extrude "wood" sheets and lumber to specified dimensions. Cement board is Portland cement poured on a bed of fiber glass mesh to create a completely waterproof "board" that can be used on floors and walls in bathrooms and other areas where wetness is a problem. Plastic and cement composition boards have become popular for exterior decks and pools and both can be colored during manufacture with a non-fade tint throughout the material. Gypsum board (or dry-wall) is simply a sheet of plaster, made in horizontal vats, then covered with thick paper, glued to both sides.
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Resources
- Photo Credit Wikimedia Commons
