Changes in physical, mechanical and chemical properties of wood during sterilisation by gamma radiation

Abstract

Gamma irradiation, which is an easy, fast and effective method for wood sterilisation, changes molecular structures not only in pest cells, but also in wood cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness, as demonstrated by experimental data. The influence of gamma radiation on maximum swelling (a MAX ), resistance to impact milling (RIM), and the total amount of water-soluble carbohydrates (TSC) was investigated. Cobalt ( 60 Co) was used as a gamma source and Scots pine wood (Pinus sylvestris L.) was irradiated at doses of 30, 90 and 150 kGy. A strong linear correlation was found between TSC and radiation dosage. Leached irradiated specimens showed significantly greater TSC content than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters improved. Gamma radiation had no significant effect on a MAX and the time elapsed after irradiation did not influence a MAX , RIM or TSC.

Changes in Selected Properties of Wood Caused by Gamma Radiation

“…Hasan (2006) and Despot et al (2007; found a strong influence of gamma irradiation on TSC. As gamma radiation causes destruction of cellulose chains and the resulting smaller cellulose fragments are easily soluble, increasing of TSC with increasing radiation dose was expected.…”

“…Hasan (2006) and Despot et al (2007; measured the total amount of water-soluble carbohydrates (TSC) according to Rapp et al (2003). They used the following procedure: Five oven-dried specimens of each group were milled together for 60 s in a heavy vibratory disc mill (Herzog Maschinenfabrik, Osnabrück, Germany).…”

“…Thus, the extraction of soluble carbohydrates appeared to be a sensitive method to display degradation of carbohydrates (Hasan, 2006;Despot et al, 2007; and is therefore also considered as a suitable tool to characterize the treatment intensity of gamma radiation.…”

“…3. Correlation between total amount of water-soluble carbohydrates relative to controls (TSC r ) and gamma radiation dose (G) for non-leached and leached specimens (Despot et al, 2007).…”

“…Curling and Winandy (2008) reported that density of southern pine sapwood stayed unchanged by any tested level of irradiation dose or dose rate of gamma radiation. Hasan (2006) and Despot et al (2007) measured oven dry mass of Scots pine (Pinus sylvestris) specimens. They determined no statistically significant changes in mass before and after irradiation at a confidence interval of 95 % although specimens were gamma irradiated in plastic bags with the presence of air ( Figure 5).…”