Abstract
Building structures made from fir wood are often attacked by wood-destroying insects for which the terpenes it contains serve as attractants. One of the possibilities for extending the lifetime of structures is to use older wood with a lower content of terpenes and/or thermally modified wood. The study evaluated the levels of terpenes in naturally aged fir wood (108, 146, 279, 287 and 390 years) and their decrease by thermal treatment (the temperature of 60 °C and 120 °C, treatment duration of 10 h). Terpenes were extracted from wood samples by hexane and analyzed by gas-chromatography mass-spectrometry (GC-MS). The results indicate that recent fir wood contained approximately 60 times more terpenes than the oldest wood (186:3.1 mg/kg). The thermal wood treatment speeded up the release of terpenes. The temperature of 60 °C caused a loss in terpenes in the recent fir wood by 62%, the temperature of 120 °C even by >99%. After the treatment at the temperature of 60 °C the recent fir wood had approximately the same quantity of terpenes as non-thermally treated 108 year old wood, i.e., approximately 60–70 mg/kg. After the thermal treatment at the temperature of 120 °C the quantity of terpenes dropped in the recent as well as the old fir wood to minimum quantities (0.7–1.1 mg/kg). The thermal treatment can thus be used as a suitable method for the protection of fir wood from wood-destroying insects.
Highlights
There are several types of monoterpenes in fir wood, α-pinene, β-pinene, limonene, Δ3-carene, camphene, β-phellandrene and myrcene
Wood is currently being used more and more for construction purposes due to its advantageous properties. It shows some disadvantages such as flammability and low resistance to fungi and insects. It is said in the construction practice that log houses, roof timber, ceilings and others structures made of soft wood are more resistant against an attack by wood-destroying insects if they are produced from older seasoned wood from which monoterpenes have vaporised and/or transformed into other compounds
Structures made of fresh timber with higher levels of monoterpenes are more liable to the attacks of H. bajulus beetles as well as other species of wood-destroying insects
Summary
There are several types of monoterpenes in fir wood, α-pinene, β-pinene, limonene, Δ3-carene, camphene, β-phellandrene and myrcene. It shows some disadvantages such as flammability and low resistance to fungi and insects It is said in the construction practice that log houses, roof timber, ceilings and others structures made of soft wood are more resistant against an attack by wood-destroying insects if they are produced from older seasoned wood from which monoterpenes (or higher terpenes as well) have vaporised and/or transformed into other compounds. Structures made of fresh timber with higher levels of monoterpenes are more liable to the attacks of H. bajulus beetles as well as other species of wood-destroying insects. The obtained results can be useful to the thermal sterilisation of buildings attacking by wood-borer insect and/or at the thermal treatment of wood dedicated to building purposes
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