Moisture conditions in coated wood panels during 24 months natural weathering at five sites in Europe

Grüll, Gerhard; Truskaller, Michael; Podgorski, L.; Bollmus, Susanne; Windt, Imke De; Suttie, Ed

doi:10.1080/17480272.2013.771212

Cited by 17 publications

(23 citation statements)

References 6 publications

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“…Earlier studies have focused on treated or untreated softwood as substrate for coatings (Creemers et al 2002, Nejad and Cooper 2011, Grüll et al 2013. Few studies incorporate tropical hardwoods (Roux M.L.…”

Section: Introductionmentioning

confidence: 99%

Outdoor weathering performance parameters of exterior wood coating systems on tropical hardwood substrates

et al. 2014

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Wood coating research almost exclusively focuses on softwood as substrate despite the fact that coatings applied on tropical hardwoods show a different weathering behaviour. The objective of this study was to quantify the impact of wood substrate and coating type on the weathering behaviour of finished wooden joinery in outdoor exposure using a set of statistical methods. Therefore, a broad range of white opaque paints and mid-oak semitransparent stains were used. The coatings were industrially applied on window frames made of frequently used commercial tropical hardwood species. The general appearance of the wood/coating systems was assessed visually using a rating scale that takes into account the anatomical characteristics of hardwood. A minimum required exposure time for evaluation of 2.5 years outdoor weathering for joinery in vertical position and facing south-west was determined. At 30 months best performances were recorded for waterborne alkyd primers with an acrylic topcoat when dry coating film was sufficiently thick. The dry layer thickness also affected the impact of the hiding power on the performance of the wood/coating system. Within hardwood species the degradation rate of coatings on species with a fine texture was the lowest. The significant influence of the substrate's texture on the weathering behaviour of coated hardwood stressed the need to evaluate the wood/coating system in total.

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Section: Introductionmentioning

confidence: 99%

Outdoor weathering performance parameters of exterior wood coating systems on tropical hardwood substrates

et al. 2014

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“…Cracking is often selected to indicate the end of the service life of coatings, and the need for maintenance [23,24]. Coating cracking will lead to higher fluctuations of wood moisture content, especially during winter [25], which encourages colonization by staining fungi. Our results have shown that the growth of blue stain fungi was not due to cracking development, and could start before visible cracking was noticed.…”

Section: Discussionmentioning

confidence: 99%

Fungal Growth on Coated Wood Exposed Outdoors: Influence of Coating Pigmentation, Cardinal Direction, and Inclination of Wood Surfaces

2019

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Four coating systems were exposed for one year outdoors at 45° south. They consisted of solventborne (alkyd based) and waterborne (acrylic based) systems in both clear and pigmented versions. Fungal growth visually assessed was compared to fungal enumeration, and the influence of exposure time on the main fungal species was studied. Results clearly showed that fungal growth was lower on the pigmented coating systems compared with their pigment-free versions. Although the clear solventborne coating included a higher amount of biocide, it was more susceptible to blue stain than the pigmented version. A new multifaceted exposure rig (MFER) also contributed to the study of fungal growth. It allowed samples to be exposed with nine different exposure directions and angles. Exposure using this MFER has shown that the worst cases (highest area and intensity of blue stain fungi) were for samples with the clear coating system exposed to north 45° and at the top of the MFER (horizontal surfaces). For any cardinal direction, all surfaces inclined at 45° displayed more blue stain fungi than vertical surfaces, due to a higher moisture content of the panels. Depending on the cardinal direction and the orientation, some surfaces were free of visible cracking, but colonized by fungi. It was concluded that the growth of blue stain fungi was not linked with cracking development.

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“…18 Sunlight radiation causes increased temperatures on a coated surface. Grü ll et al 19 explained the lower MC of samples with darker coatings with the higher energy absorption from sunlight. Elevated temperatures could also decrease the growth of microorganisms on the surface.…”

Section: Introductionmentioning

confidence: 99%

“…The protective properties of a coating decrease through weathering degradation with corresponding brittleness and crack formations in the coating. 19 Hence, the properties of the wood substrate will be emphasized with increased weathering. For example, coated sapwood spruce develops a similar cracking as uncoated sapwood spruce with increased weathering.…”

Section: Introductionmentioning

confidence: 99%

The influence of coating color, heartwood and sapwood, on moisture content and growth of microorganisms on the surface during outdoor exposure of Norway spruce boards

Sjökvist

Blom

2019

J Coat Technol Res

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The use of wood contributes to the global transformation into a bio-based community. There are, however, challenges. The growth of mold, rot fungi, and algae on the coated surface is of major concern due to decreased aesthetic service life and shorter maintenance intervals. The colonization of a coated surface requires the presence of spores, nutrients, and a sufficient amount of water. This work studied the influence of using heartwood and sapwood on the moisture content (MC) and growth of microorganisms on the surface of coated Norway spruce boards [Picea abies (L.) Karst.]. The results revealed a relationship of heartwood samples having a lower MC and a lower or equal degree of biological growth on the coated surface than sapwood samples. The relationship was valid through a range of densities (309-548 kg/m 3 ) and two different coating systems based on either an alkyd or an acrylic resin. Furthermore, the choice of coating color (red compared to white) affected the MC as the red-colored samples had a lower MC, combined with no growth of microorganisms.

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Moisture conditions in coated wood panels during 24 months natural weathering at five sites in Europe

Cited by 17 publications

References 6 publications

Outdoor weathering performance parameters of exterior wood coating systems on tropical hardwood substrates

Outdoor weathering performance parameters of exterior wood coating systems on tropical hardwood substrates

Fungal Growth on Coated Wood Exposed Outdoors: Influence of Coating Pigmentation, Cardinal Direction, and Inclination of Wood Surfaces

The influence of coating color, heartwood and sapwood, on moisture content and growth of microorganisms on the surface during outdoor exposure of Norway spruce boards

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