Multiplex plate
Veneer plywood panels ( VP = V eneer P lywood), which are usually between 4 mm and 50 mm thick and consist of at least five veneer layers of the same thickness, are referred to as multiplex panels (sometimes not yet abbreviated in accordance with the standard : MPX) . If the plate is coated with phenolic resin on both sides , it is called a screen printing plate.
Like classic plywood panels, multiplex panels are made from an uneven number of veneer layers, but plywood panels have different thicknesses. As a rule, plywood panels consist of three approx. 2–5 mm thick veneer layers glued crosswise in the middle of the panel, which are closed off from the outside by two much thinner, usually 0.6–1 mm thick veneer layers.
construction
The wood layers of multiplex boards are mostly made of birch , more rarely beech with a thickness of 0.8–2.5 mm. The number of veneer layers varies depending on the total thickness (up to 80 mm) and the desired look from 5 to 35 or more layers. The visible surfaces of the panels can also vary widely.
The panels are pressed with waterproof glue (phenol, phenol / resorcinol , or resorcinol and melamine resin ) as a binder and glued together crosswise. Cross-gluing refers to veneer layers glued together crosswise by 90 °, other angles are also possible.
The specific weight of a 19 mm beech multiplex is approx. 800 kg / m³; with birch multiplex approx. 650 kg / m³.
Aligning the grain against each other increases the dimensional accuracy of the panels, as wood expands ( swell ) or contracts (shrinkage) across the grain due to the increase or decrease in moisture . The layers are extremely resistant to tension along the grain. Changes in the size of a layer are largely prevented by the neighboring layers.
Quality levels
| Appearance classes of the surfaces | description | |
|---|---|---|
|
to
EN DIN 635-2: 1995-08 and EN DIN 635-3: 1995-08 |
out of date, still in use here and there | |
| E. | A. | Plywood, completely knot-free, slight color bleeding possible, light. |
| A bleached | Plywood, bleached and completely knot-free, no color runs, very light. | |
| I. | AB or B | Plywood, almost knot-free, color runs are possible, light. A few healthy, overgrown knots are possible, but rarely. |
| II | B or S | Plywood with small, not fancy and firmly grown knots, paint streaks are possible. Knot holes up to 8 mm possible, putty is allowed. |
| III | BB | Plywood with branches. Unusual or leveled knots as well as paint streaks and small cracks in the top layers are possible. Knot holes up to 15 mm and putty are allowed. |
| IV | C or WG | Plywood with knots, fancy knots, as well as cracks and all natural defects. Wood defects that have not been filled or defects in the top layers are also possible. |
If the quality of the surfaces of the front and back is different, quality levels can be combined. I / II stands for B. for the front: almost knot-free, light. Back: small, not unusual knots possible, paint streaks, putty spots possible.
Gluing quality
The panels are sold in the following glues according to the intended use:
- IF20: indoors, drying rooms. Adhesives: stretched urea-formaldehyde adhesives
- IF67: Indoors, damp rooms such as bathroom, shower, kitchen. Adhesives: urea-formaldehyde adhesives or melamine-formaldehyde adhesives
- A100: outside area, but protected from the weather. Adhesives: modified urea-formaldehyde adhesives or melamine-formaldehyde adhesives
- AW100: outdoors, exposed to the weather. Adhesives: phenol-formaldehyde adhesives or resorcinol-formaldehyde adhesives
execution
Paintwork (clear, colored) is possible, as well as cladding with metal. A combination with structuring of the surface, e.g. B. to increase the slip resistance.
A widespread special form of the multiplex panel is the screen printing panel (also screen-film panel) in which both surfaces are coated with phenolic resin . These are mainly used where weather resistance and a non-slip surface are important. To prevent penetration of z. B. To prevent water, the usually uncoated front sides and cut edges must be sealed separately. The screen-film plate is roughened on both sides or on one side, as a film-film plate it is smooth on both sides. The screen printing plate has no relation to the screen printing process .
Multiplex panels are also available from retailers with premium face veneer ( knife veneer ) with the usual types of wood such as B. maple, oak or cherry are offered. The thickness is then usually 19.6 mm (18 mm + 2 x 0.8 mm precious veneer). The board core consists of a normal 18 mm birch multiplex board.
application
Multiplex panels are used wherever robustness and dimensional stability are important, e.g. B. at:
- Interior and exterior cladding even with strong weather influences
- Roof and concrete formwork
- load-bearing structures
- Stairs
- Heavy-duty connecting parts in timber and timber frame construction
- Countertops, workbenches
- Base cabinets for aquariums
- Counters
- Loudspeaker enclosure
- Flight cases
- Stage construction
- Construction of triple clamps for bamboo bicycles
- Vehicle construction, e.g. B. Floors of truck bodies
- as a carrier layer for prefabricated parquet
Pakka wood
Multiplex molded parts were developed and patented under the brand name Pakkaholz by the Will Adams Plastic Company , which were first used as material for the handles of household knives by the WR Case & Sons Cutlery Company in the late 1940s . The use of pakka wood in medium brown tones began after the Second World War; from the early 1960s it was also used in darker versions as a substitute for bones as handle material for pocket knives.
See also
- Chipboard
- Hard fiberboard
- Wood wool lightweight panel
- Medium-density fibreboard
- Medium hard wood fiber board
- Chipboard
- Blockboard
- Soft wood fiber board
Web links
- ↑ Specific weights of various wooden panels. Retrieved July 13, 2020 .
- ^ Shirley Boser, John Sullivan: WR Case & Sons Cutlery Company . Arcadia Publishing, 2006, p. 72.
- ↑ Steve Pfeiffer: Collecting Case Knives: Identification and Price Guide . Krause Publications, 2011, p. 78f.