Engineered wood

Wood-based materials are materials, which are produced by grinding wood and subsequent joining of the structural elements. Size and shape of the wood particles eventually decide on the type of wood material and its properties. The wood particles may be joined together with or without binders or mechanical connections.

Description

Wood materials can consist of different types of ground wood, which differ mainly by their size. Among the largest structural elements include cutting wood, especially boards, veneers, and different thickness. Small elements make wood chips of different size ( coarse to fine particles ), wood chips, wood wool, wood fibers and dusts dar. addition to wood, other lignocellulosic materials such as cereal straw, hemp shives or Miscanthus can be used.

Properties

The properties of wood-based materials vary greatly with the size and shape of the wood particles. Compared to solid wood during the comminution of the wood changes, a number of properties. Thus increases the homogeneity of the material with increasing digestion, at the same time, however, the strength of the products and also the use of energy and the environmental impact decreases to grow over the solid wood used. The insulation properties and surface quality are improving, however. The demands on the quality of wood sink, the smaller the wood particles. So they are for glulam example, significantly higher than for particleboard.

Production

Usually a plate or strand-like wood-base materials are prepared by mixing the various types of wood particles forms of natural and synthetic binders ( adhesives ) and, if necessary, an addition of further additives, such as hydrophobing agents, wood protective agents, or coloring particles produced in the course of the subsequent hot pressing. The "new " or "innovative" wooden materials are usually processed with modern procedures of plastics technology such as extrusion or injection molding. Also, mechanical connections, for example by means of screws, dowels or tongue and groove connections are possible.

Types of wood-based materials

Wood materials can be distinguished due to the different structural elements used. We distinguish materials on solid wood base, veneer materials, clamping materials, fiber materials and composites of different structural elements.

Solid wood materials and veneer materials

As solid wood materials or materials on solid wood base wooden materials are summarized, based on solid wood elements, especially boards or sticks, are based. In contrast, there are wood-based materials on plywood base of thin peeled veneers. Solid wood and plywood materials differ substantially correspond to the thickness of the wood elements used, both can be made ​​according to each rotated 90 ° both as plywood from successive layers bonded or laminated wood with parallel layers. In the former, the fibers of the visible surfaces extend on both sides parallel. The number of layers is therefore usually an odd number.

The wood materials on solid wood base are belong:

  • Plywood board ( also referred to as solid wood boards or glued ) are querverleimt at the thicker board layers. Board plywoods can be one or more layers and wall, roof or ceiling panels mainly used as load-bearing. Solid wood panels with thicknesses greater than 12 inches are usually manufactured as hollow structures.
  • Glulam and other board stack constructions in which the grain of the board layers is mostly rectified. The boards can be simply glued or mechanically nails, dowels or tongue and groove or dovetail systems connected.
  • Blockboard, Laminated wood or other rod-shaped elements made ​​of solid wood glued
  • Solid wood elements from cross-laminated boards, which are connected by dowels and nails and are used as large components, for example, in building houses. This may be present as elements walls complete with cut-out windows and doors.

Wherein the solid wood materials have especially the quality of the wood used, the type of the compound, the layer structure and the cutting direction effect on the strength properties of the material. Thus, for example to increase the carrying capacity of a laminated timber when board layers are used with high strength in the outer layers. The cutting direction affects the resistance, there are, depending on their voltages within the material.

The classification of plywood materials are applied as with the full wooden materials primarily for the plate structure, and in the case of the plywood due to the small thickness of the elements used a greater range of variation is possible. The wood materials on plywood base are belong:

  • Veneer plywood ( FU) - has a high resistance to deformation by querverleimte veneers. This includes the multiplex boards with up to 35 layers of veneer.
  • Laminated veneer lumber
  • Strand lumber
  • Bending plywood - usually three layers, the middle layer is thinner than the outer. As the name says, can this plywood places easily bend without breaking (usually up to the diameter of a wine bottle )

Plywood materials are manufactured uncoated usually, but can also be coated with different materials. This includes in particular melamine ( formica ), but also linoleum and other materials. Special veneer plywood are also painted, metal- reinforced, or fungicide - protected. A special feature is the laminated densified wood (KP ), is impregnated with the plywood with resin, especially phenolic resin and compressed under high temperatures to a wood material with very high density and strength.

Hinnweis: As defined in DIN 1052:2008-12 include glulam beams plywood and laminated veneer lumber without transverse layers not in the group of wooden materials. All fiber dominated properties are retained in the said through cross-section. These materials are used as a rule, such as whole wood, ie as a rod- shaped components. Only when changing the original fiber structure, eg with laminated veneer lumber with cross layers or OSB arise woodwork in the true sense. Components of these wood-based panels can be used as plates or disks.

Wood chip materials

Wood chip materials are produced from wood chips, resin glue and additives under heat and pressure. The wood chips are won with hackers and special Zerspanermessern from full and sawmill residues. We distinguish the following sub- types:

  • Flat pressing plate ( P2), commonly referred to as chipboard
  • Extruded disk
  • Chip wood moldings
  • (Also known as OSB ) Coarse particle board
  • Clamping strip wood ( LSL)

Wood chip materials are the most important wood-based materials worldwide with a wide range of applications. Accordingly, there are a number of classification features ( after preparation, surface, shape, size, structure or purpose) for the classical particle board and OSB board and the many special applications. A standardized classification can be made according to EN 309.

Wood fiber materials

Wood fiber boards are made ​​of wood, sawmill by-products or waste wood, but also from other wood fiber-containing plants such as flax or canola. The structural cohesion is mainly due to the entanglement of the wood fibers and their own wood binding forces, it can also be used as binders adhesives. Depending on the manufacturing method ( wet or dry web formation ) and compression of the wood fibers are divided into the following subgroups: For wood fiber plates, which were prepared using the wet method:

  • The wood fiber insulation board (HFD ) (also porous fiberboard and "Soft Board" ( SB) ) is of low density ( 230-350 kg / m³ ) are its use for heat and sound insulation in construction, a board material. Fibrous porous sheets can be bound with bitumen.
  • The Medium-hard fiber board ( MB ) is a plate material with a density of 350 to 800 kg / m³.
  • The hard fiber board ( HB or HFH ) (also called " hardboard ") with a density of about 800 kg / m³ is used for formwork, interior, doors, furniture and packaging.

Extra hard fiberboard ( HFE) have showed a significantly higher density.

In wood fiber board, produced in a dry process:

  • The medium-density fiberboard (MDF ) is produced in the drying process. It solves by their homogeneity, higher strength and better surface properties increasingly from the flat pressed particle board (P2).
  • The high- density fiber board (HDF ) is made with glue -soaked and under pressure and heat pressed wood fibers that have been especially highly compressed. It is used as a carrier material for high load at low material thickness (eg, laminate floors).

Fiberboard low density without adding glue are mainly used as insulating materials. Even ultra light fiberboard ( ULDF ) there are on the market. A standardized classification can be made according to EN 216.

Composites

Composites are characterized in that they consist of different materials. They can consist of both different wood fragments as well as from wood and other materials such as plastics, concrete or paper. The type of the composite can vary greatly.

Examples of wood composites are

  • Wood plastic composites or wood-polymer materials are melt processable composites of wood, plastics and additives, which are usually processed with modern procedures of plastics technology. In the GDR, these composites were manufactured with the trade name Prestofol.
  • Lightweight panels with high-strength outer layers and a lighter wood core materials, foam, balsa wood or honeycomb ( honeycomb paper plates)
  • Laminated compressed wood, also known as Lignostone, is a condensed in the autoclave material based on wood, invented in 1915 by Fritz and Hermann Pfleumer. It is produced today from pressed together with resin beech wood veneers.

Composite board made from OSB middle layer and MDF top layers

Cement bonded particleboard

Profile block of wood-plastic composite

Other

  • Arbo, also known as liquid wood, is a thermoplastic processable material from lignin and cellulose, which can be processed with the established plastic processing forms such as injection molding, extrusion, compression molding, thermoforming and blow molding. This innovative wood material has been found in many small product series application.

Binders and additives

Binder play in the production of wood-based materials play a central role, as the proportion of binder for particleboard is 8-10 %, with innovative bio-materials such as wood-plastic composites, there are even more than 20 %. While containing in conventional wood materials especially formaldehyde resins are used as binders, there are at the Wood Plastic Composites usually health safer plastics or even bioplastics. Binders from renewable resources are indeed in development, playing in the wood products industry but practically no role. Other additives in wood-based materials can be: flame retardants, wood preservatives, water repellents, hardeners, etc.

The use of wood-base materials

Wood-based materials are used primarily in the construction and furniture industries. For plywood, there is a wide range of applications as a building material, insulation fibreboard are used in particular. The furniture industry is main customer of particle board - about 50 % of particleboard manufactured in Germany are to furniture (cabinets, shelves, tables, lounge seating furniture, etc. ) processes. International competitive and intended for export are mainly high quality and innovative furniture ( systems). In addition, wooden materials are used in the automotive industry and as a packaging material application.

Economic Importance

For the wood products industry include wood fiber, chipboard, OSB panel and solid wood board manufacturer and the veneer and plywood producers. In 2008, the wood-based panel industry had 15,000 direct employees. The 71 businesses achieved sales of around 5.6 billion euros a year. Wood materials are much cheaper than solid wood usually. Germany is the largest producer of wood-based panels in Europe. About 10 % of the forest wood are used in Germany for the production of wood-based materials. In 2008, 7.5 million m³ of particleboard, produces about 1 million cubic meters of OSB, 3.9 million cubic meters of MDF and 175,000 m³ of plywood. After the traditional wood-based materials in Europe and Germany for years in some cases high growth rates had, broke the production in 2008, with the exception of Wood Plastic Composites ( WPC) in comparison to the previous year: -2% to -9.3 % in the plywood at the MDF. The particle board and OSB production decreased by 6-7 % on average. In Europe, the wood material production fell by an average of 8-9 % to approximately 56 million m³. Only the Wood Plastic Composites recorded an increase in production by 78% in Germany.

Environmental effects

Concerns regarding the use of wood-based materials, there is with regard to emissions of pollutants. Here formaldehyde are particularly led from the binders, but also volatile organic compounds (VOCs), which are derived from the wood itself (eg terpenes ). Formaldehyde emissions from the binders are used by some manufacturers avoided by the use of formaldehyde-free adhesive (eg polyurethane adhesive). Furthermore, the numerous additives such as flame retardants, wood preservatives, water repellents or hardener must be checked for their environmental impact. In addition to the origin of the wood for wood materials (certification) it is primarily the binders and additives which determine the sustainability of wood-based materials.

Documents

Binder (material) Woodchips Lignocellulosic biomass Glued laminated timber cross laminated timber Miter joint Oriented strand board Linum Fritz Pfleumer Arboform
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