Resistência biológica e colorimetria da madeira termorretificada de duas espécies de eucalipto

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 and T. 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 of G. applanatum, which was classified as resistant. T3 and 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.