Avaliação da estabilidade térmica e da cinética de degradação de espécies de madeiras provenientes da região amazônica

Abstract

In this work, the correlation between wood components (cellulose, hemicellulose, lignin and extractives) and the thermal stability of three species of the Amazon Region was investigated by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry and by using of Kissinger, Flynn-Wall-Ozawa and Criado methods. The species studied were Cedrela odorata L. (Cedar), Marmaroxylon racemosum Ducke Killip (Angelim brindle) and Tectona grandis (Teak). Infrared spectroscopy evidenced that the species Teak and Angelim have more intense bands of holocellulose and lignin, while the Cedar has more discrete bands. The Teak has also the most intenses peaks for crystalline cellulose, while the Angelim demonstrated the typical band of amorphous cellulose more intense. The thermogravimetric results showed that in the temperature range between 180-220 °C the Cedar presents the most significant mass loss, beginning its degradation process around 130 °C, while the Angelim is near 205 °C and Teak around 190 °C, indicating a higher content of extractives in Cedar as well as low thermal stability in relation to the other species analyzed. The kinetic analysis showed that the three species has different degradation mechanisms according to the conversion, being the activation energy relatively constant until the conversion of 50%. Criado method showed that the wood degradation mechanism occurs by diffusion processes when the conversion is also less than 50%. The results show the lower thermal stability of Cedar in relation to the other species and the extractive content accelerates, in general, the thermal degradation of the wood (sic).