engleski

Water vapour permeability of wood-based panels finished with water-borne and solvent-based coating

One of the most important factors affecting the application area of wood-based panels is their affinity to water and water vapour. The consequences of uncontrolled moisture flows and moisture accumulation can be severe: mold growth, decay, corrosion, staining, and even structural failure [1]. Affinity to water vapour can be reduced by using a variety of coatings for wood and wood-based panels [2]. In this study, the permeability of coated and uncoated 12 mm thick plywood and particleboard was examined. Plywood is a strong thin wood-based panel consisting of two or more veneers glued together with the grain direction of veneers at a 90˚ angle. Particleboard is manufactured by pressing mixed wood particles with a suitable resin. Particleboard is mainly used in furniture productions and has become popular as a construction material due to its numerous usage possibilities and inexpensive cost [3]. A total of three types of commercial coatings was used and dried in room conditions: transparent one-component water-borne acrylic coating, transparent two-component water-borne polyurethane coating and transparent two-component solvent-based polyurethane coating. Water vapour permeability properties was determined by cup method based on EN ISO 12572:2016. Four samples were made of each type of coated and uncoated panels. Conditioned samples were sealed on the top of the cups with neutral silicone and aluminium rubber seal tape to ensure water vapour loss through the defined test surface area. An initial mass of samples was recorded, and samples were left in laboratory conditions at 23 ± 2 °C and 50 ± 5 % relative humidity. Changes in sample weight were recorded every day for the next 40 days. The results showed a higher water vapour permeability on particleboard samples compared to plywood samples. Moreover, water vapour permeability on particleboard samples was intensive in the first 10 days after which it was equalized. However, water vapour permeability on plywood samples was very small in the first 5 days after which it increases sharply. The water vapour permeability of the water-borne coatings was higher than the water vapour permeability of the solvent-base coating on both types of panels. Also, the water vapour permeability of the polyacrylate coating was higher than the water vapour permeability of the polyurethane coating on both types of panels. The lowest water vapour permeability was recorded on panels finished with two-component solvent-based polyurethane coating, and the highest water vapour permeability was recorded on uncoated panels and then on panels finished with transparent one-component water-borne acrylic coating.

water vapour permeability, wood-based panels, water-borne coating, solvent-based coating

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