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

Abstract

Wood samples of red pine (Pinus resinosa) were subjected to freezing for 60 h at a temperature of -20°C and then thermally modified in soy oil at a temperature of 220°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.

Thermochemical and physical properties of two fast-growing eucalypt woods subjected to two-step freeze–heat treatments

“…Parameters of thermal treatments performed in this study were defined based on a pilot experiment and previous scientific works [4,7,12,18,19,21].…”

“…Nevertheless, in some cases this variation of extractives is small and insignificant. According to Hart [17], Ilic [7] and Awoyemi et al [18], specific extractives tend to rearrange or to migrate toward the inside of the wood cell wall, increasing the radial permeability and possibly creating more pathways through the pits.…”

“…A successful combination of thermal treatments has been reported in the literature, such as hydrothermolysis followed by heat treatments at high temperatures [19,20], and wood freezing as a pre-treatment followed by heat treatments [18,21]. Thus, this study aimed to evaluate the effects of two-step freeze-heat treatments on thermochemical and physical properties of fast-growing Rose gum (Eucalyptus grandis Hill ex Maiden) and Gympie messmate (Eucalyptus cloeziana F.…”

Physical and Mechanical Properties of Fast-Growing Wood Subjected to Freeze-Heat Treatments

“…Such treatments include a two-stage impregnation and heat treatment (Perçin et al 2015;Lahtela and Kärki 2016); magnetization followed by furfurylation (Dong et al 2016); boron impregnation and heat treatment (Kartal et al 2008); densification followed by oil heat treatment (Fang et al 2011(Fang et al , 2012, as well as freezing and heating treatment (Awoyemi et al 2010;Missio et al 2015Missio et al , 2016.…”

“…Interesting results were observed after treating tropical wood with a combination of freezing and heating (Awoyemi et al 2010;Missio et al 2015). The two-stage freeze-heat treatment was more efficient than just the heat treatment for water absorption, water repellence, and maximum impact strength .…”