Thermal modification influences the mechanical resistance of wood from forestry species

Abstract

This study evaluated the effects of thermal modification at different temperatures and for different durations on the mechanical strength of wood of selected species from an agroforestry system. To this end, three 9-year-old (approximate age) individuals, each from four species of forest trees-Parapiptadenia rigida (Benth.) Brenan, Peltophorum dubium (Spreng.) Taub., Eucalyptus grandis × Eucalyptus urophylla hybrid, and Schizolobium parahyba (Vell.) Blake-were evaluated. After obtaining initial measurements, samples from the four species under went heat treatment for 2 h and 4 h and were subsequently subjected to heat using an oven at temperatures 120°C, 150°C, 180°C, and 210°C; respectively, in addition to the control. For evaluating mechanical strength, the technical standard ASTM D 143-94 was used to obtain the values of the moduli of elasticity and rupture, tension at the proportional limit, and maximum force of the subjects. It was observed that different durations and temperatures altered the mechanical strength of the wood of the four species studied. The 2 h residence time is the most recommended for conducting thermal modification. This procedure modifies the mechanical resistance of wood in a positive manner, with exposure temperatures ranging between 120 ºC and 180 ºC being the most recommended. The thermal treatment carried out for 4 h is not recommended for structural purposes because of the decrease in flexural strength.

Correlation of anatomy with physical properties of wood species from an agroforestry system

“…To evaluate the influence of one parameter on another in the correlation analysis, as in the case of the anatomical and physical properties of wood, it is essential that the species studied show heterogeneity among themselves. This is an important characteristic, because heterogeneous materials are mandatory to more accurately evaluate the influence of anatomical parameters on the physical properties of wood (Eloy et al, 2023). This is justified by the fact that the different species studied have different anatomical parameters and, consequently, their physical properties differ.…”

“…When we analyze the dimensions of the fibers, we can infer that the highest CWF values found for the species P. rigida, P. dubium and E. grandis × E. urophylla are associated with the basic density, since they are directly proportional (Table 4). This relationship results in the highest values for this physical property, as well as for all other mechanical properties, making the material more resistant (Eloy et al, 2023). On the other hand, lower CWF values result in a lower basic density of the wood (Lima et al, 2014), corroborating the results found for S. parahyba, which were lower average CWF values (21.6%) (Table 2) and, consequently, lower basic density values (0.277 g cm -3 ) (Table 3).…”

“…movement. In this context, species that show rapid growth and the use of new forms of cultivation stand out as alternatives to supply this market (Eloy et al, 2023).…”

“…Therefore, products with high basic density values are suitable for uses that require greater mechanical resistance, directly influencing the machining of wood (Bandera et al, 2021). On the other hand, the higher the cell lumen values, the greater the amount of empty space in the wood, reducing the basic density, as well as the values of mechanical properties (Eloy et al, 2023).…”