|Derived lumber products||[German version]|
Derived lumber product is the term used to describe plywood boards, fiberboard and chipboard as well as „oriented strand board“ (OSB), the structure of which has been modified by mechanical and chemical processing. Using derived lumber products in box construction means that there is no risk of shrinkage and the consequent opening of joints. The four different types of derived lumber products are briefly described below.
DIN 68 705 sets out the quality requirements for plywood boards. This DIN standard also provides information concerning applications, board types and names, properties, testing and marking.
The term plywood board covers various types of boards, which consist of several (at least three) wooden sheets which are glued together with their grain directions set at an angle to one another. Depending upon the type of gluing, DIN 68 705 distinguishes the following types of boards:
|IF: Glued bond resistant only in enclosed spaces with generally low humidity (not weather-resistant)|
|AW: Glued bond resistant even on severe exposure to moisture (moderately weather-resistant)|
Common board types are veneer boards and wood core boards. Veneer boards are supplied in thicknesses of 4 – 15 mm and are relatively insensitive to dimensional changes. Many different wood species may be used in such boards. They consist of 3, 5 or 7 plies. Wood core boards, in contrast, comprise three layers, with the core consisting of conifer battens, and, at a board thickness of approx. 15 – 32 mm, they are thicker than veneer boards. They may also be considered relatively resistant to dimensional change.
Oriented strand board (OSB)
OSB competes for the same applications as plywood. Standard EN 300 „Oriented strand board (OSB)“ defines these boards, classifies them into four types and states the requirements for them.
Definition: „A multilayer board produced from long, slender strands of a defined shape and thickness bound together with a binder.“ …“
|OSB/1: Boards for general purposes and for interior fitments (including furniture) for use in a dry environment.|
|OSB/2: Boards for load-carrying purposes for use in a dry environment.|
|OSB/3: Boards for load-carrying purposes for use in a wet environment.|
|OSB/4: Boards with a high loading capacity for use in a wet environment.|
Fiberboard is produced from pressed fibers. Such board is relatively stable and resistant to moisture exposure. The characteristic feature of this type of board is that it has one smooth face and one rough face. The smooth, water-repellent face should always face outwards when used for box construction. The usual board thickness is between 2 and 6 mm and specific weight is 850 – 900 kg/m3.
In contrast with fiberboard, chipboard is produced not from fibers, but from pressed chips or flakes bound with synthetic resin binders. Depending upon the compression density, chipboard has a specific weight of between 450 and 800 kg/m3. Chipboard has the major disadvantage that it is very difficult to nail together and that cut edges easily splinter or flake. Chipboard is thus rather unsuitable for packaging applications. Due to its elevated acetic acid content and the associated risk of corrosion, chipboard must never be used inside climate-controlled packages.