Pre-freezing as a pre-treatment for thermal modification of wood. Part 2: surface properties and termite resistance

Wood samples of red pine (Pinus resinosa) were subjected to freezing for 60 h at a temperature of -20 degrees C and then thermally modified in soy oil at a temperature of 220 degrees C for 2 and 4 h. The pH, acid buffering capacities, alkali buffering capacities, surface energy and resistance to termite attack were determined. Wood, subjected to pre-freezing as a pre-treatment method, has lower surface energy, pH values and acid buffering capacity. The effects on pH and acid buffering capacity were only significant during the 2-h treatment. The effect of pre-freezing on the alkali buffering becomes noticeable only after 4 h of thermal modification. The effect of this pre-treatment method varies largely with the treatment temperature. After 2-h thermal modification, the unfrozen wood showed higher susceptibility than the frozen wood while the reverse was the case as the treatment time was increased to 4 h.