Understanding of the effect of ancestral and natural saltwater treatment on durability, fibers densification and chemical modification of palm wood

IRG/WP 18-10921

M T Elaieb, A Namsi, M Tella, M-F Thévenon, K Chandelier

The palm-tree sector plays a very important role on both the socioeconomic and ecological levels, in Tunisia. There are three million trees in Tunisian palm plantations, ensuring a potential significant wood production, mainly in the craft and furniture industries. In the past, Date Palm wood (Phoenix dactylifera L.,) was also used as structural material. Its low natural durability and its low mechanical properties were improved by an ancestral preservative method consisting in the immersion of the trunk of the palm tree trunk freshly slaughtered for a period ranging from 1 to 2 years (depending on the species) in the salt waters of the Lake of Chot Djerid. This ancestral practice was disappeared, and it is always difficult to find more information on the different parameters involved in this kind of process. The objective of this work was to assess the main technological qualities of palm wood preserved by salting while trying to retrace the steps of this natural and eco-friendly preservation process. Two Common date palm cultivars woods (Kentichi and Deglet Noor) with ages ranging from 40- to 50-years, native and preserved by salting in the Chot Djérid were used for the experiments. Each wood samples were collected at the Regional Center of Research on Oasis Agriculture - Degache - Southern Tunisia. Densities (air-dried, water saturated, basic), mechanical properties, decay and termites resistances tests were performed on native and salt water - treated palm woods. The first results showed a significant increase of the air-dried density of palm wood samples which increases after their wood salt water immersion. Salt water treatment allows improving greatly the palm wood MOR in bending and paralleling to the fibers. Termite’s resistance tests highlighted that native and treated palm wood had a similar degradation level after termite exposure, but the termite mortality rate was higher for the treated wood than that of native palm wood. Extractives, lignin and cellulose contents are slightly more abundant in the control samples except for the hemicelluloses which are more abundant in the treated palm wood sample. Additional analyses conducted with an ICP-AES 700 Agilent device, evaluating the mineral compositions between native and salt-treated palm woods, give us some explanation ways about the performance improvement of wood after such a natural preservation process.

Keywords: palm wood, chemical modification, Brining treatment, decay and termite resistance, mechanical properties

Conference: 18-04-29/05-03 Johannesburg, South Africa

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