Permeability and mechanical behaviour of microwave pre-treated norway spruce ripewood

Abstract

This is a study of the influence of microwave (MW) pre-treatment on the permeability of Norway spruce ripewood (Picea abies L. Karst) as it affects its mechanical properties. Specimens were treated under variable moisture content, MW intensity, and impregnation processes. According to the results, the specimens with an initial moisture content of 45–65% exhibited the highest permeability values compared to reference samples. An insignificant difference was found between MW pre-treatments at 2 and 3 kW. Statistically significant results were found after long-time (24h) vacuum-pressure impregnation (LP). The average retention value following LP was 132 kg.m-3, which is almost three times greater than the MW-treated groups impregnated in a short-time vacuum-pressure process. The average depth of penetration after LP was 2.0 mm and the proportion of the impregnation area following LP was 17.6%. MW pre-treatment had no effect on the impregnability or the mechanical properties of the wood; other MW regimes are open for further examination.