Artificially aged spruce and beech wood surfaces reactivated using FE-DBD atmospheric plasma

Abstract

Abstract Although weathering is usually carried out in outdoor conditions, even ageing in indoor conditions can cause significant changes to wood surfaces. We found these to notably impact wetting and coatability of surfaces of common beech (Fagus sylvatica L.) and Norway spruce [Picea abies (L.) Karst.] wood. These effects were well overcome and the surfaces reactivated using a novel kind of a plasma device. On both kinds of wood, ageing caused significant changes in their colour, opening of pits and cell wall destruction. Infrared spectra indicated a significant decrease of aromatic lignin and production of non-conjugated carbonyl groups. Surface free energies and spreading kinetics varied much upon this kind of ageing. In beech, pull-off strengths for a commercial waterborne wood coating slightly decreased for longer exposure times. For the reactivation of wood surfaces, we employed a novel approach using a floating electrode dielectric barrier discharge (FE-DBD) plasma, which had not been done on wood before. Similar to other plasma techniques, the surface free energy (SFE) increased after treatment. On beech wood, the plasma treatment (PT) led to higher pull-off strengths of the waterborne coating. On spruce wood, the coating mostly showed cohesive failures after ageing, and thus the PTs showed less improvements.