Thermo-hydro-mechanical densification of hemlock

ABSTRACT The effect of Thermo-Hydro-Mechanical densification on selected properties of western hemlock was investigated. The drive was to explore the possibility of using hemlock as a replacement for expensive hardwoods for flooring applications. Kiln-dried boards at about 12% moisture content were subjected to densification in a hot press. As a special treatment, half of the samples were surface-sprayed with water before densification and three pressing times (5, 10, and 15 min), as well as temperature levels (120°C, 160°C, and 200°C) were used. Sample density, hardness, colour change, and abrasion resistance were evaluated after densification. Data analysis revealed that the temperature level, densification time, and type of pre-treatment were statistically significant factors. Compared to controls, densification significantly improved density, hardness, and abrasion resistance by 197%, 386%, and 437%, respectively. As a possible desired aesthetic feature, this process darkened hemlock by about 200%.