Cork (material)

As cork ( phellem ) the cell layer between the epidermis and cortex is referred to in botany. In everyday use, the material from the bark of the cork oak (Quercus suber) is the term referred cork, are obtained from the mainly cork. Cork is also obtained ( Phellodendron amurense ) from the bark of the Amur cork tree Asian.

• 2.1 cork flooring 2.1.1 binder
• 2.1.2 Surface Treatment

Formation and Properties

Education

Cork is made from cork cambium ( cork cambium ) and serves as a secondary dermal tissue, especially at the points where the epidermis and the cortex of the peripheral extension of the stem axis can not follow the secondary growth in thickness. Phellogen the cork is outwardly and inwardly, a thin layer of parenchyma cells, phelloderm ( cork ), which may also contain chloroplasts. Phellem, cork cambium and phelloderm be collectively referred to as periderm.

The forming cork is species-specific and only a few cell layers thick in most plants, as is the case for example with the white Korkfahnen on birch trunks. In a few species, especially the cork oak tree, on the other hand are formed by a long activity of centimeter-thick layers of cork Phellogens. These are then divided into annual rings. When the spindle tree ( Euonymus ) and some other species corky wings are formed on young branches.

The formation of specific cork cells is done by Auflagerung ( Akkrustierung ) of suberin, a lipophilic and water- biopolymer. Thereby, the hydrophobic (water-repellent ) Effect of cork cells is ensured. As a lipophilic substance can suberin (and thus cork ) can be made visible by light microscopy using Sudan III glycerol. After completion of the wall forming the cells die off and fill up with gas, as well as tanning agents can be incorporated as a protection against invading insects that cause browning.

Properties

, Which consists of air-filled dead cells of cork is for the exchange of substances (water / gas) interspersed with lenticels that pervade the natural foam. By this Korkporen breathing the underlying epidermis is made possible. It has no intercellular spaces. Cork is hydrophobic, highly elastic and poorly combustible. The thermal conductivity of cork is very low, reflecting its suitability is explained as an insulating material.

Transpiration is already severely limited by a thin layer of cork.

Use

The particular combination and variety of physical, chemical, as well as visual features makes the cork also economically interesting in fishing as a float to fishing and networks, as a sealing material in machinery and equipment, as a bottle cap, notice board, as a floor covering, wind instruments, as orthopedic shoe inserts material as well as construction and thermal insulation.

The bark of the cork oak is processed since the 2nd century AD in the Mediterranean region, especially in Central Italy and in Spain and the former Roman province of Hispania and today mainly in the south of Portugal, peeled with Schneideäxten of stems and main branches and. In the first peeling a rough, resin-rich cork falls to that for the production of reinexpandierten dark brown cork boards (without the addition of artificial binder) is how they are used as a natural building material for thermal insulation. After that, every 8 to 12 years the younger Sekundärkorkrinde be harvested. It is little resin and largely homogeneous, so it is suitable for machine processing. The Sekundärkork is mainly used for production of bottle corks and a number of other industrial products. World leader in the manufacture of cork products is the Portuguese Amorim Corticeira.

The remains of the bottle cork production are ground to light brown granules. This can be glued to Sekundärkorkgranulat latex, polyurethane, or other adhesives in vacuum and / or under mechanical pressure so that the specific natural characteristics of the cork material to be added varied. From such artificial Agglomeratkork products with a higher strength, such as champagne corks or - cut from blocks into slices - floor coverings are made. Due to the low thermal conductivity of cork is also suitable as an insulating material, such as a cork boards or Korkschüttung, as well as caulking to seal well. Also, composites with a polymer matrix include in recent years to this spectrum (Cork -plastic composites ).

The exact amount of cork quota used in Germany there are no figures, these can be reconstructed only by trade data. So every year 900-1400 t raw cork and cork products imported 10,000 to 40,000 t, but only 30 to 80 t raw cork and 2,000 to 5,000 t cork products exported back (Federal Statistical Office 2008). Overall, according 10000-35000 t cork are processed each year in Germany.

Cork flooring

There are different types of cork surface for floor coverings: on the one hand the single cork cork flooring and on the other hand veneered, laminated flooring. The veneered cork flooring differ by an affixed Korkfurnier of the single cork cork boards. Solid cork there are only a so-called Korkmosaik. The veneer is glued to the cork cork flooring and is used primarily for decorative purposes. Another advantage is the better color cover in colored cork boards. The drawback is the worse veneered cork tiles resistance to abrasion. However, this can be significantly improved with sealing wax, so that the abrasion resistance almost reaches the massive cork flooring and cork cork boards. In addition to strong solvent-based seal coatings based on polyurethane and environmentally friendly seal water-based paints have been offered since 2002 in part.

The manufacturers sell cork floor as tiles, which can be fully glued to the subfloor and cork parquet, which is installed as a floating with tongue - and-groove systems, ie is not glued to the subfloor. Without any adhesive when laying Korkparkettsysteme come with special connections between the tiles ( "click ") systems. Since 2001, there Korkmosaik, this consists of solid pieces of cork (no granules with a binder ) is similar to stone mosaic prefabricated on a support material. It is fully bonded and subsequently grouted as stone tiles. The surface treatment can be adapted to the use similarly as with adhesive cork and cork parquet. The advantage of solid Korkmosaik lies in the extended application for outdoor areas and in wet cells.

Conventional and conventional cork tiles cork parquet made ​​of cork, which is mixed and pressed into various processes with binders.

Binder

For the manufacture of the cork granules Korkblöcken a binder is added, which supports the natural resins in the cork. As the binder the polyurethane resins or phenolic resins are used. While the former only smell for a short Auslüftungszeiten and are considered safe, evaporate residual phenols over a long period of phenolic resin binders and can burden the health of residents.

Surface treatment

There are different ways to treat the surfaces of the cork tiles. The tiles can be stained or left natural brown. Colored tiles must be subsequently treated with a sealing wax, while paint and color must be coordinated in order to avoid unwanted chemical reactions and discoloration. Oils or waxes as other means of surface treatment can be carried out at non-colored cork tiles. For Korkmosaik outdoors also colored oils such as teak oil are suitable. When laid on ships of Korkmosaik also spar varnish can be used. In order to improve the slip resistance of fine quartz sand are sprinkled into the freshly applied paint.

Architectural models

In the late 18th century came in Europe in connection with the classical educational trips and the souvenir industry and collection of casts, etc. the phelloplastic in fashion, the production of architectural models made ​​of cork. These were largely to structures from the Roman times.

Recycling

Cork has the recycling code 51 (FOR).