RESUMO -Os objetivos deste estudo foram os seguintes: a) observar o efeito de termorretificação sobre a durabilidade natural da madeira de Eucalyptus tereticornis e Corymbia citriodora após ataque de fungos causadores de podridão-branca (Trametes versicolor e Ganoderma applanatum); b) avaliar parâmetros colorimétricos após a submissão das madeiras a tratamentos térmicos e aos fungos T. versicolor e G. applanatum. Para realização do estudo, corpos de prova de ambas as espécies foram submetidos aos tratamentos: T 1 -testemunha; T 2 -autoclave (120 °C) a 1,5 kgf/cm² durante 1 h; T 3 -estufa laboratorial (180 °C) por 4 h; e T 4 -térmico combinado [120 °C (1 h) + 180 °C (4 h)]. Posteriormente, os corpos de prova foram submetidos ao apodrecimento acelerado, sendo expostos às duas espécies de fungos por 16 semanas. Após esse período, foram avaliadas a perda de massa e as variáveis colorimétricas, através dos parâmetros L*, a*, b*, C* e hº antes e depois do ataque pelos fungos. De acordo com os resultados, E. tereticornis e C. citriodora foram classificados como altamente resistentes a fungos apodrecedores, exceto no tratamento testemunha de C. citriodora submetido ao ataque de G. applanatum, o qual foi classificado como resistente. Com os tratamentos T 3 e T 4 , a perda de massa foi reduzida em ambas as espécies de madeira. As maiores mudanças nos parâmetros colorimétricos ocorreram devido ao tratamento térmico e à pouca variação observada com o ataque dos fungos apodrecedores. Houve redução da variável claridade (L*) e queda das matrizes vermelho (a*) e amarelo (b*), razão por que o tratamento térmico mostrou-se como alternativa para proteção e escurecimento da madeira de eucalipto, tornando-a mais próxima de padrões de coloração de madeiras nobres.Palavras-chave: Podridão branca; Tratamento térmico; Claridade. BIOLOGICAL RESISTANCE AND COLORIMETRY OF HEAT TREATED WOOD OF TWO EUCALYPTUS SPECIESABSTRACT -The objectives of this study were: a) to observe the effect of heat treatment on natural durability of Eucalyptus tereticornis and Corymbia citriodora wood to attack of white rot fungi (Trametes versicolor and Ganoderma applanatum); b) to evaluate colorimetric parameters after the submission of the woods to heat treatments and T. versicolor and G. applanatum fungi. To start the study, samples of both specie were submitted to the treatments: T 1 -control; T 2 -autoclave (120 °C) at 1,5 kgf/cm² for 1 h; T 3 -oven (180 °C) for 4 hours; and T 4 -thermal combined [120 °C (1 h) + 180 °C (4 h)].
The aim of the present study is to investigate the resistance of Eucalyptus botryoides treated with TiO 2 particles to attack by the fungus Ganoderma applanatum. The Bethel treatment method was applied to wood specimens (25 × 25 × 9 mm) and compared to CCB. The wood was subjected to the accelerated decay test and characterized through Rockwell Hardness and Fourier Transform Infrared Spectroscopy (FT-IR). The TiO 2 -treated wood showed lower degradation and greater resistance to the penetration of a steel sphere (Rockwell Hardness) than the untreated wood. In addition, the results of the TiO 2 treatment were statistically equal to those of CCB. The FT-IR analysis showed that the fungus degraded lignin and hemicellulose in untreated samples. The present results showed the TiO 2 efficiency in forming a protective layer on the cell wall and in preventing the development of microorganisms, a fact that verifies its fungicidal action on wood.
It was impregnated commercial titanium dioxide into Pinus elliottii wood, aiming to increase its durability against the attack of brown rot fungus Postia placenta and photodegradation caused by ultraviolet radiation. The samples were put under 8 bar pressure for 3 hours at different concentrations of TiO2 (0.5%, 0.25%, 0.124% and 0%-control). To evaluate the effect of the fungus on the wood, the test was carried out according to ASTM D2017-05 and UNE-EN 113:1996 with modifications. The photodegradation was performed by exposing a tangential section to ultraviolet radiation for 400 hours, and the colorimetric parameters were periodically evaluated. Statistically, the treatments with TiO2 did not differ among themselves, but were much lower than the control, showing the effectiveness of this product in protecting the wood against the attacks of degraders. As for the photodegradation, the treated wood remained practically unchanged, differently from the control that had a darkening accelerated mainly in the first 50 hours. With this information, it can be stated that TiO2 treated wood is able to hinder the fungus access to the cell wall, to inhibit its growth and to create a barrier that protects the polymers from photodegradation, increasing its durability and emerging as a potential alternative for wood treatment.
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