Abstract 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.

Resumen Se impregnó dióxido de titanio comercial en la madera de Pinus elliottii, con el objetivo de aumentar su durabilidad contra el ataque del hongo pardo de la Postia placenta y la fotodegradación causada por la radiación ultravioleta. Las muestras se pusieron a una presión de 8 bar durante 3 horas a diferentes concentraciones de TiO2 (0.5%, 0.25%, 0.124% y 0% de control). Para evaluar el efecto del hongo en la madera, la prueba se realizó de acuerdo con la norma ASTM D2017-05 y UNE-EN 113:1996 con modificaciones. La fotodegradación se realizó exponiendo una sección tangencial a radiación ultravioleta durante 400 horas, y los parámetros colorimétricos se evaluaron periódicamente. Estadísticamente, los tratamientos con TiO2 no diferían entre sí, pero eran mucho más bajos que el control, mostrando la efectividad de este producto en la protección de la madera contra los ataques de los degradadores. En cuanto a la fotodegradación, la madera tratada se mantuvo prácticamente sin cambios, a diferencia del control que tuvo un oscurecimiento acelerado principalmente en las primeras 50 horas. Con esta información, se puede afirmar que la madera tratada con TiO2 puede dificultar el acceso del hongo a la pared celular, inhibir su crecimiento y crear una barrera que protege a los polímeros de la fotodegradación, aumentando su durabilidad y emergiendo como una alternativa potencial para tratamiento de la madera.

ABSTRACT The aim of the present study is to investigate the resistance of Eucalyptus botryoides treated with TiO2 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 TiO2-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 TiO2 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 TiO2 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.

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 eGanoderma 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: T1 - testemunha; T2 - autoclave (120 °C) a 1,5 kgf/cm2 durante 1 h; T3 - estufa laboratorial (180 °C) por 4 h; e T4 - 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 T3 e T4, 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.

ABSTRACT 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 andT. versicolor and G. applanatum fungi. To start the study, samples of both specie were submitted to the treatments: T1 - control; T2 - autoclave (120 °C) at 1,5 kgf/cm2 for 1 h; T3 - oven (180 °C) for 4 hours; and T4 - thermal combined [120 °C (1 h) + 180 °C (4 h)]. Subsequently, the samples were subjected to accelerated decay, being exposed to both species of fungi for 16 weeks. After this period, the mass loss and the colorimetric variables through the parameters L*, a*, b*, C* and hº were evaluated before and after the fungal attack. According to the results, E. tereticornis and C. citriodora were classified as highly resistant to decay fungi, except for the control treatment of C. citriodora subject to the attack ofG. applanatum, which was classified as resistant. T3and T4 treatments reduced the mass loss for both wood species. The biggest changes in colorimetric parameters occur due to heat treatment and minimum variation was observed with the attack of decay fungi. There was a reduction in the variable lightness (L*) and red (a*) and yellow (b*) matrix, thereby the heat treatment could be an alternative to protection and darkening of eucalyptus wood approximating these to hardwood patterns.