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

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.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

“…Wood exposed to solar UV radiation typically undergoes surface discolouration and degradation that reduces its adhesive strength for coatings [ 458 , 459 ]. A novel variant of the APP technology was shown to successfully reverse moderate effects of surface degradation due to exposure to UV radiation of Fagus sylvatica (beech wood) [ 460 ]. Beech wood weathered under exposure to a xenon source in the laboratory, when subsequently treated by the novel variant of APP, showed an increase of adhesion strength by up to 20%.…”

Wood Surface Finishing with Transparent Lacquers Intended for Indoor Use, and the Colour Resistance of These Surfaces during Accelerated Aging

“…Discolouration can also occur due to daylight comprising bigger wavelengths. Consequently, there has been an evident necessity for more attention regarding the effects of indoor conditions, especially related to the discolouration of surface-treated wood, and equally native wood without surface treatment [ 40 , 41 ]. The coating materials used for surface treatment of wood products intended for indoor performance need studying as a priority (furniture, indoor sides of window frames, and similar), with the aim that the application of these coating materials on wooden products can guarantee their long-lasting colour stability.…”

Trends in Chemical Wood Surface Improvements and Modifications: A Review of the Last Five Years

“…However, they noted that it would improve the performances of solvent-borne coatings after 3024 h of artificial weathering, showing a better aging behavior. On the other hand, Zigon et al showed that the tensile strength of coatings applied on weathered wood could increase by 20% with a FE-DBD plasma pre-treatment [178]. These results were supported by Peng et al who also noted that dielectric barrier discharge plasma treatments would consequently reduce the delamination of a water-based primer applied on a beech substrate during a cross-cut test [190].…”

“…An interesting use of plasmas in wood surface modification is to oxidize its polymeric constituents to increase its surface free energy and wettability. Over the last 5 years, many workers explored this application to increase the interactions between wood and adhesives or coatings [176][177][178][179][180][181][182][183][184][185][186][187]. They found that using reactive carrier gases such as air and O 2 would lead to the creation of polar groups such as carboxyl and carbonyl at the surface of the treated wood, increasing its hydrophilicity and surface free energy.…”