title: Permeability of cork to gases.
abstract: The permeability of gases through uncompressed cork was investigated. More than 100 samples were assessed from different plank qualities to provide a picture of the permeability distribution. A novel technique based on a mass spectrometer leak detector was used to directly measure the helium flow through the central area of small disks 10 mm in diameter and 2 mm thick. The permeability for nitrogen, oxygen, and other gases was measured by the pressure rise technique. Boiled and nonboiled cork samples from different sections were evaluated. An asymmetric frequency distribution ranging 3 orders of magnitude (roughly from 1 to 1000 μmol/(cm·atm·day)) for selected samples without macroscopic defects was found, having a peak below 100 μmol/(cm·atm·day). Correlation was found between density and permeability: higher density samples tend to show lower permeability. However, boiled cork showed a mean lower permeability despite having a lower density. The transport mechanism of gases through cork was also examined. Calculations suggest that gases permeate uncompressed cork mainly through small channels between cells under a molecular flow regime. The diameter of such channels was estimated to be in the range of 100 nm, in agreement with the plasmodesmata size in the cork cell walls.
authors: Center for Physics and Technological Research-CEFITEC, Physics Department, Faculty of Sciences and Technology, Universidade Nova de Lisboa, Portugal.
authors: David P
authors: DP
authors: Faria
authors: Ana L
authors: AL
authors: Fonseca
authors: Helen
authors: H
authors: Pereira
authors: Orlando M N D
authors: OM
authors: Teodoro
mesh_terms: D005740:Gases; D010539:Permeability; D029963:Quercus
chemical_list: D005740:Gases