The Search for Durable Exterior Clear Coatings for Wood

Evans, Philip D.; Haase, Jonathan G.; Seman, A. Shakri B.M.; Kiguchi, Makoto

doi:10.3390/coatings5040830

Cited by 87 publications

(105 citation statements)

References 61 publications

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“…The results of the conducted experiments (Figures 2-7, Table 4) confirmed that the development of durable transparent surface protection for wood exposed to external conditions is complicated, and that the field of research in this area is still open [66]. This fact was emphasized even more through the use of oak as the underlying wood species.…”

Section: Resultssupporting

confidence: 48%

“…The remaining treatments were characterized by a significant colour change compared to untreated oak wood (Figure 2), which was associated with a certain darkening after their application (see Table 2), and subsequent leaching by water associated with more significant changes in colour parameters (L*, a* and b*). Based on the results, it can be concluded that the use of UV-stabilizers only increases the colour stability of underlying wood if their leaching in external conditions is further prevented by a high-quality coating film [66]. According to the experimental results, using only the hydrophobic layer does not provide protection for the wood for a long period of time.…”

Section: Resultsmentioning

confidence: 80%

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Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

et al. 2017

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Abstract:The durability of transparent coatings applied to an oak wood exterior is relatively low due to its anatomic structure and chemical composition. Enhancement of the protection of oak wood against weathering using transparent hydrophobic coatings is presented in this study. Oak wood surfaces were modified using UV-stabilizers, hindered amine light stabilizer (HALS), and ZnO and TiO 2 nanoparticles before the application of a commercial hydrophobic topcoat. A transparent oil-based coating was used as a control coating system. The artificial weathering test lasted 6 weeks and colour, gloss, and contact angle changes were regularly evaluated during this period. The changes in the microscopic structure were studied with confocal laser scanning microscopy. The results proved limited durability against weathering of both tested hydrophobic coatings. The formation of micro-cracks causing the leaching of degraded wood compounds and discolouration of oak wood were observed after 1 or 3 weeks of the weathering test. Until then, an oil-based coating film had protected the wood sufficiently, but after 6 weeks the wood was fully defoliated to its non-homogenous thickness, which was caused by the presence of large oak vessels, and by the effects of specific oak tannins. Using transparent hydrophobic coatings can prolong the service life of the exteriors of wood products by decreasing their moisture content. Without proper construction protection against rainwater, the hydrophobic coating itself cannot guarantee the preservation of the natural appearance of wood exteriors.

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Section: Resultssupporting

confidence: 48%

Section: Resultsmentioning

confidence: 80%

Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

et al. 2017

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“…Future work will involve construction and testing of this proposed low cost device. As well as application to automotive coatings, the combination of the low cost LF-OCT device and graph search segmentation could be used for industrial coatings on wood [2] and in aerospace applications, such as thermal barrier coatings for aerospace turbine blades [49]. It may also be used for the automatic measurement of pharmaceutical tablet coating thicknesses [50].…”

Section: Discussionmentioning

confidence: 99%

“…Examples of this variety are the heavy industry clear top coats in modern car paint systems [1], the do-it-yourself varnishing of outdoor wooden objects [2], and the highly specialised varnish coatings for valuable works of art [3]. This paper is focused on the economically important industrial coating context [1,4].…”

Section: Introductionmentioning

confidence: 99%

Scan-Less Line Field Optical Coherence Tomography, with Automatic Image Segmentation, as a Measurement Tool for Automotive Coatings

et al. 2017

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Abstract:The measurement of the thicknesses of layers is important for the quality assurance of industrial coating systems. Current measurement techniques only provide a limited amount of information. Here, we show that spectral domain Line Field (LF) Optical Coherence Tomography (OCT) is able to return to the user a cross sectional B-Scan image in a single shot with no mechanical moving parts. To reliably extract layer thicknesses from such images of automotive paint systems, we present an automatic graph search image segmentation algorithm. To show that the algorithm works independently of the OCT device, the measurements are repeated with a separate time domain Full Field (FF) OCT system. This gives matching mean thickness values within the standard deviations of the measured thicknesses across each B-Scan image. The combination of an LF-OCT with graph search segmentation is potentially a powerful technique for the quality assurance of non-opaque industrial coating layers.

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“…Samples were attached to separate aluminium stubs using nylon nail polish and coated with a 10 nm layer of gold to make them electrically conductive. A scanning electron microscope fitted with a high brightness lanthanum hexaboride electron source (Cambridge Stereoscan 360, Leica Microsystems, Wetzlar, Germany) or a variable pressure scanning electron microscope (S-2600N, Hitachi Ltd., Tokyo, Japan) was used to obtain images of the tangential surfaces of samples after sanding or planing, and again after wetting and drying [17]. Loose material present at sanded or planed surfaces, both before and after wetting, was removed using transparent tape, and the tape was mounted on aluminium stubs and imaged using a scanning electron microscope, as above.…”

Section: Grain Raising Of Sanded Versus Planed Woodmentioning

confidence: 99%

Microstructure and Mechanism of Grain Raising in Wood

et al. 2017

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Grain raising, the lifting of fibres when water is applied to wood surfaces, is a reason why some companies are reluctant to finish wood products with water-borne coatings. However, the elements that lift-up and cause grain raising have not been identified, and the relationship between wood density and grain raising has not been clarified. Our work sought answers to both questions. We planed or sanded different woods using aluminum oxide abrasive paper, and characterized surfaces using profilometry and SEM. Surfaces were re-characterized after wetting and drying. Grain raising is inversely related to wood density. In particular, very low-density woods are highly susceptible to grain raising, whereas grain raising does not occur in high-density woods or planed woods. In low-density woods, sanding tears cell walls creating loosely-bonded slivers of wood that project from surfaces, particularly after wetting and drying. This mechanism for grain raising was confirmed by modelling the action of abrasives on wood cell walls using an array of hollow tubes and a serrated tool. Less commonly, fibres and fibre-bundles project from surfaces. We observed that grain raising was correlated with the coarseness of the abrasive and conclude that it can be reduced in severity by tailoring sanding to account for the density and surface microstructure of wood.

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The Search for Durable Exterior Clear Coatings for Wood

Cited by 87 publications

References 61 publications

Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

Scan-Less Line Field Optical Coherence Tomography, with Automatic Image Segmentation, as a Measurement Tool for Automotive Coatings

Microstructure and Mechanism of Grain Raising in Wood

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