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Cork

Page history last edited by Thomas Kutzli 11 years, 7 months ago

 

Quercus suber, commonly called the Cork Oak, is a medium-sized, evergreen oak tree in the section Quercus sect. Cerris. It is the primary source of cork for wine bottle stoppers and other uses. It is native to southwest Europe and northwest Africa.

It grows to up to 20 m, although it is typically more stunted in its native environment. The leaves are 4 to 7 cm long, weakly lobed or coarsely toothed, dark green above, paler beneath, with the leaf margins often downcurved. The acorns are 2 to 3 cm long, in a deep cup fringed with elongated scales.

The tree forms a thick, rugged bark containing high levels of suberin. Over time the cork cambium layer of bark can develop considerable thickness and can be harvested every 9 to 12 years to produce cork. The harvesting of cork does not harm the tree, in fact, no trees are cut down during the harvesting process. Only the bark is extracted, and a new layer of cork regrows, making it a renewable resource. The tree is cultivated in Spain, Portugal, Algeria, Morocco, France, Italy and Tunisia.

Cork's elasticity combined with its near-impermeability makes it suitable as a material for bottle stoppers, especially for wine bottles. Cork stoppers represent about 60% of all cork based production.

Cork's low density makes it a suitable material for fishing floats and buoys, as well as handles for fishing rods (as an alternative to neoprene).

Sheets of cork, often the by-product of more lucrative stopper production, are used to make bulletin boards, and when used as floor tiles and other building materials, because it is a good insulator, it can reduce the energy required for heating.

Granules of cork can also be mixed into concrete. The composites made by mixing cork granules and cement have lower thermal conductivity, lower density and good energy absorption. Some of the property ranges of the composites are density (400–1500 kg/m³), compressive strength (1–26 MPa) and flexural strength (0.5–4.0 MPa).

 

Other uses: Cork is used in musical instruments, particularly woodwind instruments, where it is used to fasten together segments of the instrument, making the seams airtight. Conducting baton handles are also often made out of cork.

Cork can be used as bricks for the outer walls of houses, as in Portugal's pavilion at Expo 2000.

On November 28, 2007, the Portuguese national postal service CTT issued the world's first postage stamp made of cork.

Cork is used as the core of a baseball. Replacing the interior of a baseball bat with cork—a practice known as corking — was historically a method of cheating at baseball; the efficacy of the practice is now discredited.

Cork is often used, in various forms, in spacecraft heat shields.

Also is used inside footwear to improve climate control and comfort.

Corks are also hung from hats to keep insects away. See cork hat.

Cork has been used as a core material in sandwich composite construction.

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