Effects of Heat Treatment on the Characteristics of Royal Paulownia (Paulownia tomentosa (Thunb.) Steud.) Wood Grown in Korea

Abstract

Effects of heat treatment on the characteristics of Royal paulownia (Paulownia tometosa) wood were investigated. The results were compared with those of Suwon silver poplar (Populus tementiglandulosa) and Korean red pine (Pinus densiflora) woods. The wood samples of the three species were treated at 160°C, 180°C, 200°C and 220°C in an electric furnace for 2 hours. The changes of color, density, mass loss, and relative crystallinity were investigated before and after heat treatment. The lightness (L*) decreased rapidly from 200°C in all species. There were no change in red-green chromaticity(a*) and yellow-blue chromaticity(b*) of Royal paulownia and poplar woods with increasing temperature. Whereas, yellow-blue chromaticity(b*) of Korean red pine wood decreased sharply from 200°C. Royal paulownia wood showed appreciable color change(ΔE*) after heat treatment above 180°C. Poplar and pine woods, however, presented significant color change from 160°C. Color change of the three wood species increased rapidly with increasing temperature. Mass loss of the three wood species by heat treatment was the highest in the Royal paulownia wood and the lowest in the pine wood. Mass loss and relative crystallinity increased and density decreased slightly with increasing temperature. Consequently, it is revealed that Royal paulownia wood showed considerable differences in the temperature of color change, weight loss and change of relative crystallinity compared to the other wood species.