Sorption isotherms and moisture transfer properties of seven Central Africa hardwood species

ABSTRACT

The aim of this article is to characterize the wood-water relationship and certain moisture transfer properties of Central African species for which very little data exists in the literature, i.e. Iroko, Padouk, Bibolo (Dibetou), Moabi, Doussié, Bilinga and Grenadilla. Moisture sorption isotherms were measured using the Dynamic Vapor Sorption method at 35°C. The Hailwood-Horrobin model was used to describe the sorption isotherm and the model parameters are given for each species. A rough estimation of the fiber saturation point could be made and is between 18.5% for Doussié and 26.5% for Bibolo. The water vapour diffusion coefficient in the radial direction of the wood was determined by the cup method at 35°C. Its value ranges from 1.72E-11 for Grenadilla to 1.71E-10 m²/s for Bibolo. It has been shown that the model proposed by Siau (1984) allows a relatively reliable estimation of the value of this parameter from wood density. The gas permeability was also measured on the same samples and ranged from 3.3E-19 m² for Moabi to 3.78E-16 m² for Bibolo. From these parameters, the apparent tortuosity and equivalent pore diameter for the mass flow were estimated for each species.

KEYWORDS:

• Sorption isotherm
• vapour diffusivity
• gaseous permeability
• tropical woods

Acknowledgements

The authors would like to thank Adèle Miquau and Mélanie Serruys for their assistance for the tests on Grenadilla wood, which was supplied by the factory Buffet Crampon in Mantes-la-Ville (France), whom we also thank.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Part of this work was financed by the International Tropical Timber Organization (ITTO) awarded to Dr. Merlin Simo-Tagne (ITTO Ref. Grant: 022/19A).