Growing in Portugal and Mediterraneancountriessuch as: Spain, France, ItalyorAlgeria, Morocco and Tunisia, the species of oakQurqusSuber L, calledcorkoak, providesus with anextremelyvaluable and uniquerawmaterial - cork bark. Thereis no othernaturalmaterialthatwouldsimultaneouslycombinesomanyvaluableproperties, whichmeansthatthismaterialhasbeenused by man for decades for manydifferentapplications - from bottlecorks, throughvarioustypes of decorative and insulating materials commonlyused in constructionorindustry, to materials used in astronautics. Over the years and with the development of modern technologies, the scope of itsusecontinues to expand.
However, beforethispreciousrawmaterial in itsvariousmaterialformsfindsitswayintoindustry, our homes, officesorsimplyintobottles of goodwine, corkoakmustgrowquietly for about 25 years. Onlyaftersuch a period of timedoes the exploitation of corktreesbegin, whichinvolves stripping patches of bark from theirtrunks and branches. The first of these, calledvirgin, isveryirregular and relatively hard, soitismainlyused to makeveneersordecorative products. Eachsubsequentstrippedlayer of bark ismoreregular and softer, and isprimarilyused to makenaturalstoppers - corkstoppers for bottles. In order for a bottlestopper to be cut from a properlycut piece of bark, the bark sheetspulled from the treeundergoappropriateprocessing, i.e. aging, boiling, straightening, drying and selectionintodifferentgrades of materialdepending on theirthickness and quality.
The waste materialgenerated in the process of manufacturingbottlecorks, as well as all the remainingrawmaterialthatdoes not meet the appropriatequalityrequirements for theirproduction, provides a materialbase for the production of alltypes of agglomeratedcork materials, such as sheets, rolls, corkpaneling, corkflooring, etc.
The process of barkingcorkoaks in Portugal, whichis the largestproducer of corkrawmaterial (itproducesabout 50% of the world'sstock), takes place every 9 years. Duringthis period, the treeisable to fullyadditsprotectivelayer, whichis the bark, against the influence of the hot southern climate. The barkingprocess to thisdayiscarried out manually, by experiencedworkers, usingtraditionaltools - specialaxes.
Bark growthvaries from year to year, depending on the weatherconditionsprevailing in a givenyear, i.e. temperature and the amount of rainfall.
The method of exploitingcorkoaksmakesitpossible to obtain a valuablerawmaterial and protect the environment at the same time.
Cork owesitsspecialproperties to itsuniqueinternalstructure. Having the form of tetrahedralcorkcells (thereareabout 40 million of them in 1 cm³) with flexiblewalls, theyarefilled with a gas with air-likeproperties and connected to eachother by capillaries. With the help of thesethintubules, thisgascan be removed from individualcells, e.g. as a result of a compressiveforce, as well as "sucked" backinto the elasticcellswhen the actingforceissubtracted. Thisfeaturemakeseachcorkcell a miniaturethermal, acoustic and vibrationinsulator.
The maincomponents of naturalcorkaresuberinabout 45%, lignin 27%, polysaccharides 12%, wax 6% and tanninsabout 6%.
- excellentthermal and acousticinsulation and vibrationisolationparameters
- high mechanicalresistance and compressibility
- resistance to the effects of manysubstances and chemicalcompounds
- resistance to fungi and mold
- lowflammability and lack of emission of toxiccompoundsduringburning
- antistaticity and anti-allergenicity
- easy to process
- high coefficient of friction
- goodinsulation from the influence of harmfulradiation of emissionwaterveins and other materials