Effects of Hot Water Treatment on the Structure and Properties of Cork

Authors

  • M. Emília Rosa
  • Helena Pereira
  • M. A. Fortes

Keywords:

Cork, hot water treatment of cork

Abstract

The cork used for stoppers (reproduction cork) is subjected to a boiling operation before processing, which consists of immersing the cork boards in boiling water for approximately one hour. An experimental study of the hot water treatment was undertaken with the purpose of characterizing the alterations that it may cause in the structure, dimensions, mass and compression properties of cork.

Various parameters related to the treatment were investigated, including water temperature, time, cork quality, and the kinetics of open air-drying.

The major structural alteration due to boiling is the attenuation of cell-wall corrugations. This leads to an expansion of 10-15% in the radial direction and 5-7% in directions perpendicular to this, including the axial and tangential directions. The mass is virtually unaffected. Boiling causes a softening of cork and also a reduction of its elastic anisotropy. These and other observed changes in the stress-strain curves in compression can be explained in terms of the structural changes.

References

Fortes, M. A., and M. E. Rosa. 1988. Factors affecting the density of cork. Cortiça 593:65-68.nGibson, L. J., K. E. Easterling, and M. F. Ashby. 1981. The structure and mechanics of cork. Proc. R. Soc. Lond. A377:99-117.nNatividade, J. V. 1938. What is cork? Boletim da Junta Nacional da Cortiça 1:13-21.nNatividade, J. V. 1950. Subericultura. Ministério da Economia—Direcção Geral dos Serviços Florestais e Aquícolas, Lisboa.nPereira, H., M. 1988. Chemical composition and variability of cork from Quercus Suber L. Wood Sci. Technol. 22:211-218.nPereira, H., M. Ferreira, and M. G. Faria. 1979. Analysis of extraction water in the industrial processing of cork. Cortiça 493:493-496.nPereira, H., M. E. Rosa, and M. A. Fortes. 1987. The cellular structure of cork form Quercus Suber L. IAWA Bull. 8(3):213-218.nRosa, M. E., and M. A. Fortes. 1988a. Rate effects on the compression and recovery of dimensions of cork. J. Mat. Sci. 23:879-885.nRosa, M. E., and M. A. Fortes. 1988b. Temperature induced alterations of the structure and mechanical properties of cork. Mater. Sci. Eng. 100:69-78.nRosa, M. E., and M. A. Fortes. 1988c. Stress relaxation and creep of cork. J. Mat. Sci. 23:35-42.nRosa, M. E., and M. A. Fortes. 1989. Effects of water vapour heating on the structure and properties of cork. Wood Sci. Technol. 23:27-36.n

Downloads

Published

2007-06-22

Issue

Number 2 / April 1990

Section

Research Contributions

License

The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:

1. All proprietary rights other than copyright, such as patent rights.

2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.

3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.