Efeito da modificação térmica nas propriedades da madeira de mogno africano (Khaya ivorensis A. Chev.)

Abstract

Brazil is recognized for having one of the largest biodiversity in the world. In relation to forest resources, wood is one of the main. The Brazilian monkey (Swietenia macrophylla) as a result of the exploitation, is scarce and, therefore, the reduction of the supply and increase of prices in the national and international market and also by being attacked by Hypsipyla grandella (pointer drill). Aiming to circumvent such problems was introduced in Brazil, the African mahogany (Khaya sp.). There was a good acceptance of the market, having characteristics similar to Brazilian mahogany and being resistant to pointer drill, motivating the growth of planted areas in Brazil. With such economic potential but with shortcomings in relation to works that address the technological knowledge of this wood. Thus, this research aimed to evaluate the effect of the thermal modification on the properties of African mahogany (Khaya ivorensis). For both, were evaluated the sampling position of the pieces in the logs, in two levels and thermal modification temperature. The effect of the thermal modifications on the technological properties was evaluated on colorimetry; chemical analysis; physical and mechanical properties, and termites biological tests were carried out (dry wood and subterranean termites). For the thermal treatments performed (180 and 200 °C) a color enhancement of African mahogany wood was observed, and a more uniform color was obtained. Thermally modified heartwood became less hygroscopic, dimensionally more stable and less dense, at both temperatures (180 and 200 °C). The moisture content of equilibrium, apparent density and tangential swelling decreased with increasing temperature from 180 to 200 °C. As for the elastic modulus (stiffness), both static and dynamic, it was generally observed that they increased with the elevation of the thermal treatment temperatures (180 and 200 °C). The best temperature for the improvement of wood resistance to dry wood termites (Cryptotermes brevis) and subterranean termites (Nasutitermes corniger) was 180 °C, as it promoted higher mortality and faster death of insects. Finally the temperature of 180 °C was the most favorable for the thermal modification of tested African mahogany wood.