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The cellular structure of cork from Quercus cerris var. cerris bark in a materials’ perspective |
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| Authors: | Ali ?en Teresa Quilhó Helena Pereira |
| Institution: | a Istanbul University, Faculty of Forestry, Department Forest Biology and Wood Protection Technology, 33473 Bahçeköy, Istanbul, Turkey b Centro das Florestas e Produtos Florestais. Instituto de Investigação Científica Tropical, Tapada da Ajuda, 1349-017 Lisboa, Portugal c Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal |
| Abstract: | Cork in the outer bark of trees is among the valuable raw materials of biological origin due to properties that result mainly from its cellular structure. Large scale commercial utilization of cork has been only achieved with cork from Quercus suber. Another oak species, Quercus cerris, also contains substantial, albeit not continuous, regions of cork that are clearly visible to the naked eye but are so far considered as a waste material.Bark samples of Q. cerris var. cerris trees were collected from the And?r?n province, Turkey. Cork portions were separated and their cellular structure was investigated with optical and electron scanning microscopy observations. The results were compared with Q. suber cork.Q. cerris cork has the typical features of cork tissues with a regular and radially aligned structure of suberized cells without intercellular voids, showing a ring structure and a distinction of earlycork and latecork cells. Solid volume fraction was estimated at 25% (22% in earlycork, 36% in latecork).In Q. cerris cork cells are smaller, cell wall thickness and solid volume fraction are higher, and the tissue is less homogeneous with a higher content of lignified inclusions than in Q. suber cork. These factors will negatively influence quality in regard to density and mechanical properties associated to elasticity. However, this does not impair its use for production of granulates and agglomerates, e.g. for insulation and energy absorption. Separation of the cork fraction from the bark is a step required before further processing and use. |
| Keywords: | Quercus cerris Cork Cellular structure Bark Quercus suber |
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