Reducing the set-recovery of surface densified solid Scots pine wood by hydrothermal post-treatment

Abstract

The mechanical properties of wood surface are of particular interest in applications where mainly the surface is exposed to use, such as flooring boards. Wood surface densification aims to improve these properties by compressing only the first few millimeters beneath the surface. Scots pine (Pinus sylvestris L.) sapwood was surface densified to three degrees of compression at 150 °C using a specially designed heated press. Half of the specimens were hydrothermally post-treated at 200 °C. To study the influence of the degree of compression and hydrothermal post-treatment on the set-recovery, specimens were subjected to water soaking-drying-cycles. The surface densification process resulted in a minor mass loss regardless of the degree of compression, whilst the hydrothermal post-treatment led to an average mass loss of 3.8 % in surface densified specimens and of 4.1 % in control un-densified specimens. Furthermore, considerable fixation of compressive deformation was obtained by hydrothermal post-treatment at 200 °C.