Influence of impregnation, chemical and thermal wood modification on properties related to sorption, tensile strength and resistance to Fenton’s reagent

Heat treatment (HT) of wood at temperatures above 200°C efficiently reduces the degradation by treatment with Fenton`s reagent (FT), i. e. the formation of hydroxyl radicals are supressed, as evidenced by the mass loss (MLFT) and tensile strength loss TSLFT data. One reason for the reduced degradation by the Fenton’s reagent (FR) might be the pre-degradation of the cell wall polymers during HT. Another one is the inhibition of the FR process. Fe ions dissolved in acetate buffer are hardly able to penetrate into cell walls of HT wood with high MLHT. This inhibits both the production of hydroxyl radicals in the direct vicinity to the cell wall polymers and the reduction of ferric ions. In addition to thermal pre-degradation of wood constituents, the decay resistance of HT wood towards the FR might be explained with the retarded penetrability due to the smaller cell wall nano-pores and and the lower moisture contents due to minor swelling ability. High resistance of HT wood to brown rot fungi might thus be attributed to the fact that the FR process is inhibited because the complexed Fe ions cannot penetrate the modified cell wall which is a prerequisite of incipient decay.