Abstract

Thermally modified hardwood species, e. g. limba, is now being marketed in Europe for cladding and other external applications. The timber is supplied from West Africa and treated thermally in the EU. This approach opens very good possibilities for commercialisation of lesser-known tropical wood species that are hardly used nowadays. The objectives of the study were to treat thermally metil (Sterculia appendiculata) and neem (Azadirachta indica) timber originating from Mozambique under industrial conditions applying two well-recognized methods namely thermal treatment by steam (Thermowood (R)) and under vacuum (Termovuoto (R)). Matched boards were treated in industrial facilities under identical treatment conditions (temperature of 212 C, duration 3 h). Colour changes were characterised with CIELab method and it was proved that the thermal modification under vacuum generates lighter colour than that caused by steam treatment. Mass loss of the boards were measured; the difference was statistically significant for the mass loss being higher in Thermowood (R) process namely, 9.9% after vacuum and 14.1% after steam thermal treatment for metil and 12.1 and 14.2% for neem respectively. This probably can be explained by the fact that the applied vacuum removes partly the produced acetic acid from the material which catalyses sugar degradation. On the other hand, anatomical and chemical features may also play a significant role concerning the applied atmosphere. For instance, it should be noted that metil wood is more permeable than neem wood. In general the mass loss is an important predictor for the mechanical properties that are expected to be somewhat lower after thermal modification. Both thermal treatments showed good ability to mask fungal discolouration which is typical for the processing conditions in the tropics.

Keywords

colour; fungal discolouration; mass loss; metil; neem; thermal modification

Published in

Book title: Eco-efficient Resource Wood with Special Focus on Hardwoods: Sopron, 8-9 September 2016 : Proceedings
eISBN: 978-963-334-291-6
Publisher: University of West Hungary

Conference

7th Hardwood Conference on Eco-Efficient Resource Wood with Special Focus on Hardwoods, SEP 08-09, 2016, Sopron, HUNGARY

Authors' information