Brittleness increase inEucalyptuswood after thermal treatment

Abstract

Thermal treatments arise as an alternative to increase the physical and biological properties of wood, though they usually cause a reduction in mechanical strength. Therefore, the aim of the study was to determine the brittleness of Eucalyptus wood submitted to freezing and heat treatments. Freezing occurred with green condition specimens and the heat treatment with samples in equilibrium moisture content (20°C and 65% RH). The static bending test was carried out on an EMIC® universal testing machine. The freezing showed slight changes in the mechanical properties of Eucalyptus wood, not differing from natural wood. The treatments with high temperatures caused significant losses in mechanical strength, evidenced by decreases in maximum load and increases in brittleness. In the combined treatments, there was no sum of effects. Therefore, heat treatments modify the mechanical properties of wood, increasing its brittleness and following the tendency that, as the temperature increases, the mechanical resistance decreases.

Propose of models to estimate toughness as a function of physical and chemical properties of commercial thermally modified hardwoods

“…Observing the behavior of physical, chemical and mechanical properties, the coefficient of variation (CV) increases with elevation of thermal treatment temperature. Such performance is corroborated by literature [6,35,[44][45][46][47], which can be explained by a major degradation of wood constituents and wood hysteresis [31,46,48], increasing the inherent material variability after thermal modification.…”

“…One form to possibility and encourage to use thermally treated hardwoods is to use models to estimate physical, chemical and mechanical properties as a function of thermal treatment temperature. It is consolidated on the literature that thermal treatment temperature interferes on wood properties, being possible to correlate the increase of temperature with raise or reduction of wood properties [23,[31][32][33][34][35]. Such generalization of models for hardwoods is possible due the similarity of wood anatomy and constituents on this wood class [36][37][38].…”

Determination of the Elastic Modulus of Brazilian Tropical Wood at High Temperatures Using the Impulse Excitation Technique (IET)

“…The main changes in wood subjected to high temperatures occur in the degradation of hemicellulose by deacetylation, depolymerization, and dehydration, as well as in structural changes and rearrangement of lignin (Dalla Costa et al 2020). These chemical changes, primarily the degradation of hemicellulose, are considered responsible for the decrease in mechanical properties, as evidenced by reduced resistance to force application (Wentzel et al 2019;Oliveira et al 2022).…”

Enhancing mechanical and surface properties of Eucalyptus wood

“…In this context, a wood modification process that enhances mechanical and surface properties and also homogenises the different species is necessary. These modification methods, whether of thermal treatments or also using densification, are currently used by researchers in different species, such as Pinus caribaea and Eucalyptus saligna (Brito et al 2019), Eucalyptus nitens (Wentzel et al 2019), Eucalyptus grandis and Eucalyptus cloeziana (Dalla Costa et al 2020), Fagus sylvatica and Quercus robur (Laskowska 2020), Populus usbekistanica (Sözbir et al 2019), aiming at increases in the technological properties of wood. The densification process suites well to this purpose because it is proven to significantly increase the mechanical and surface properties of wood (Welzbacher et al 2008, Pertuzzatti et al 2018.…”