Investigations into the influence of two different wood coatings on water diffusion determined by means of neutron imaging

Abstract

The diffusion of water into spruce wood coated with an acrylate/polyurethane and with a silica-based coating system is investigated by varying the humidity conditions. Thereby, the change of moisture content (MC) is measured and analysed with the non-destructive method of neutron imaging. For the acrylate/polyurethane based coating system, the barrier effect of the coating on wood sorption in direct water contact and the influence of surface defects on this barrier effect are also tested. On changing the humidity conditions, the specimens with silica-based coating initially show a clear deceleration of the sorption process, whereas after 10 days the MC gradient is nearly similar to the uncoated reference specimens. In contrast, the specimens with acrylate/polyurethane based coating show a strong barrier effect against water sorption into wood over the whole measurement period when changing the humidity conditions and in direct water contact. As can be expected, a defect in the coating strongly reduces its barrier effect. Thereby, the kind of defect (saw kerf or blade cut) is rather irrelevant.

Selected previous findings on the factors influencing the gluing quality of solid wood products in timber construction and possible developments: A review

“…For example, digital image correlation was used to measure crack initiation and crack propagation in adhesive joints under load (Knorz et al 2016). Atomic force microscopy (AFM), scanning electron microscopy, and related nanoindentation (NI) techniques enable the determination of the mechanical properties of the wood cell wall at the nanometer scale (Sonderegger et al 2015, Casdorff et al 2018, Bockel et al 2020. A similar level of observation can be achieved by analyzing the materials in situ when performing tests in a synchrotron.…”

“…Chemical wood modification is a well-accepted solution, even at the expense of high raw material costs. An alternative approach is surface treatment, where protective coatings/films reduce moisture uptake and slightly increase the resistance of the wood to moisture diffusion (Sonderegger et al 2015, Volkmer et al 2015.…”

Using Thermal Neutron Imaging in Forest Products Research

“…Despite its potential, the technique has not been widely used in wood and forest products research. The limited existing research has focused on investigating moisture uptake and water transport effects in various wood-based products [5][6][7][8], including woodplastic composites [9]. While, others have used the technique to measure local density variations across growth rings [10].…”

The Implication of Benzene–Ethanol Extractive on Mechanical Properties of Waterborne Coating and Wood Cell Wall by Nanoindentation

“…Wood often suffers from water damage [16][17][18] because of the hydrophilicity of its chemical components [19]. Coatings can protect wood from directly contacting water and prevent wood surface from degradation [20][21][22]. Coating solid wood has the advantage of enhancing its natural beauty and its physical and chemical properties.…”