Effect of thermal modification on some physical and mechanical properties of yellow poplar (liriodendron tulipifera)

Thermal modification is a treatment method used to improve some properties of wood in order to expand its range of usage and extend its lifetime. Although it generally causes a worsening of mechanical properties, some of them can change due especially to lower equilibrium moisture content when compared with untreated wood. Therefore, we wanted to compare some properties of thermally modified and untreated samples having either the same moisture contents or those of the area of use. For this purpose, we tested untreated and thermally modified (at 180° C for 3 hours) yellow poplar (Liriodendron tulipifera) solid wood samples. We investigated density, swelling and shrinkage ratios, and anisotropy of shrinkage as physical properties, and compression and bending strength, modulus of elasticity and impact bending as mechanical properties, according to the relevant ISO standards. The results showed that thermal modification increased the dimensional stability while having a negative impact on the mechanical properties (except modulus of elasticity) at the same moisture content, as indicated in the literature. However, thermally modified samples with moisture content as in the area of use exhibited improved properties (except in the case of impact bending).