Special Issue "Wood Coatings"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (31 August 2017).

Special Issue Editor

Guest Editor
Dr. Mojgan Nejad Website E-Mail
Department of Forestry, Michigan State University, East Lansing, MI 48824, USA
Interests: development of green bioproducts (coatings, adhesives, and foams)

Special Issue Information

Dear Colleagues,

The growth of multi-story wooden building constructions in recent years, as well as the positive consumer and industry attitudes toward sustainable materials, has opened many more opportunities for wood products. These developments have led to a larger market for wood coatings. Throughout the last few decades, wood coating formulators have dealt with a few major changes in the industry, such as the transition from solvent-based to water-based or UV-Cure formulations, the development of coatings for Cu-based preservative treated wood upon the phase out of CCA, and the formulation of coatings for heat-modified or acetylated wood in exterior applications. Many researchers have also devoted their time to studying the applications of nanoparticles and renewable materials in wood coating formulations and their performance on wood.

This Special Issue of “Wood Coatings” is intended to invite researchers within the field from across the world to publish their latest work in an online coating journal. Since there is no journal exclusively dedicated to wood coatings, this issue will serve as a starting point for gathering all the researchers in wood coatings. As such, the Special Issue may also be seen as a comprehensive compendium for students interested in pursuing research in wood coatings, and as a resource for industries looking for experts in the field.

Dr. Mojgan Nejad
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Keywords

  • exterior wood coatings
  • interior wood coatings
  • weathering performance
  • renewable materials
  • nanocoatings
  • treated wood
  • UV-Cure coatings
  • engineered wood products

Published Papers (9 papers)

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Research

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Open AccessArticle
Synergistic Effect of Addition of Fillers on Properties of Interior Waterborne UV-Curing Wood Coatings
Coatings 2018, 8(1), 9; https://doi.org/10.3390/coatings8010009 - 23 Dec 2017
Cited by 6
Abstract
A waterborne ultraviolet (UV)-curing coating was prepared on the surface of wood materials with modification of talcum powder and calcium carbonate (CaCO3). When the waterborne UV-curing coatings on the surface of wood materials (WUVCW) was radiated for 1 min by UV [...] Read more.
A waterborne ultraviolet (UV)-curing coating was prepared on the surface of wood materials with modification of talcum powder and calcium carbonate (CaCO3). When the waterborne UV-curing coatings on the surface of wood materials (WUVCW) was radiated for 1 min by UV (λ = 365 nm) and dried at 40 °C for 10 min, it showed good hardness, adhesion, and impact strength, with controlling the talcum content of 2.0% and CaCO3 content of 1.0%, respectively. When the content of talcum powder was higher than 2%, the mechanical properties and gloss of the WUVCW decreased, and when the talcum powder of WUVCW increase to more than 5%, a matte surface appeared after curing. When CaCO3 and talcum powder were present at the same time, the mechanical properties of WUVCW were better than those of only CaCO3 or talcum powder. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessCommunication
Evaluation of Selected Properties of Alder Wood as Functions of Sanding and Coating
Coatings 2017, 7(10), 176; https://doi.org/10.3390/coatings7100176 - 21 Oct 2017
Cited by 7
Abstract
The objective of this study was to optimize the sanding and coating processes of black alder wood to promote and support its use in furniture manufacturing. Two criteria have been applied for process optimization, namely, the minimum surface roughness of the samples and [...] Read more.
The objective of this study was to optimize the sanding and coating processes of black alder wood to promote and support its use in furniture manufacturing. Two criteria have been applied for process optimization, namely, the minimum surface roughness of the samples and power consumption during sanding as a function of various sanding systems. The surface roughness of the sanded specimens and the power consumption during sanding strongly depends on the grit size used. Two eco-varnishes were applied to the samples by spraying. Moreover, the effect of the surface preparation and varnish type on the coating properties expressed by the varnish layer adherence to the substrate and surface glossiness was evaluated. For better glossiness values, the UV-cured varnish was preferred. The sanding with a grit sequence of 60, 120, and 150 grit size abrasives was found to be optimal when applied to black alder wood, and it is recommended to obtain performant UV-coated wood surfaces for furniture products. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessArticle
Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering
Coatings 2017, 7(10), 172; https://doi.org/10.3390/coatings7100172 - 18 Oct 2017
Cited by 10
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 [...] Read more.
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 TiO2 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. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessArticle
Atmospheric Pressure Plasma Coating of Wood and MDF with Polyester Powder
Coatings 2017, 7(10), 171; https://doi.org/10.3390/coatings7100171 - 17 Oct 2017
Cited by 5
Abstract
In this study, polyester powder based on iso- and teraphthalic acid was deposited with an atmospheric plasma jet. The powder was fed into the effluent plasma zone and deposited on European beech wood (Fagus sylvatica L.), Grand fir (Abies grandis Lindl.) [...] Read more.
In this study, polyester powder based on iso- and teraphthalic acid was deposited with an atmospheric plasma jet. The powder was fed into the effluent plasma zone and deposited on European beech wood (Fagus sylvatica L.), Grand fir (Abies grandis Lindl.) and medium density fiberboard (MDF). The substrates were annealed subsequent to the coating process. To exclude decomposition of the polyester layers by the plasma treatment, the surface chemistry of the layers has been examined by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) and compared with the polyester powder reference. Furthermore, topographical investigations were carried out using laser scanning microscopy (LSM). Adhesive strength of the layers was evaluated by dolly test and gloss measurements with a goniophotometer. The deposited layers showed no chemical changes compared to the reference. The adhesive strength of the layer met practical requirements of >1 MPa. It was demonstrated that the deposition of a macroscopic layer is possible without a pretreatment or the usage of additives. Therefore this coating process by atmospheric pressure plasma for wood and wood based materials could represent an environmental-friendly alternative to conventional coating methods. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessArticle
Influence of Coating Formulation on Its Mechanical Properties and Cracking Resistance
Coatings 2017, 7(10), 163; https://doi.org/10.3390/coatings7100163 - 30 Sep 2017
Cited by 1
Abstract
The mechanical properties of coatings strongly influence wood coatings’ performance, as coatings may be stressed by dimensional variations of wood when exposed outdoors. Within the European project SERVOWOOD (2014–2016), the influence of coating formulation on mechanical properties and cracking resistance has been studied. [...] Read more.
The mechanical properties of coatings strongly influence wood coatings’ performance, as coatings may be stressed by dimensional variations of wood when exposed outdoors. Within the European project SERVOWOOD (2014–2016), the influence of coating formulation on mechanical properties and cracking resistance has been studied. Several acrylic and alkyd formulations with different pigment volume concentrations (PVCs), with and without UV protection have been applied on pine samples and exposed to artificial weathering (EN 927-6) for 12 weeks. Persoz hardness of coatings applied on wood was assessed before and after weathering. Tensile tests on free films have been carried out at −10 °C, 20 °C, and 45 °C. For each formulation, elastic modulus, tensile strength, and strain at break have been determined for the three test temperatures. For each test temperature, there was no correlation between the elastic modulus and strain at break, nor between tensile strength and strain at break. The results showed a relation between Persoz hardness and elastic modulus. The best performing formulation had a mean elastic modulus at room temperature lower than 400 MPa and a mean strain at break higher than 30%. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessArticle
Microstructure and Mechanism of Grain Raising in Wood
Coatings 2017, 7(9), 135; https://doi.org/10.3390/coatings7090135 - 29 Aug 2017
Cited by 4
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Wood Coatings)
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Review

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Open AccessReview
Role of Moisture in the Failure of Coatings on Wood
Coatings 2017, 7(12), 219; https://doi.org/10.3390/coatings7120219 - 02 Dec 2017
Cited by 1
Abstract
Most wood coating tests are done either in a short term artificial weathering chamber or long term on an outdoor rack/fence. In both cases, the coatings are exposed to both ultraviolet radiation and water. This study is focused on the influence of moisture [...] Read more.
Most wood coating tests are done either in a short term artificial weathering chamber or long term on an outdoor rack/fence. In both cases, the coatings are exposed to both ultraviolet radiation and water. This study is focused on the influence of moisture alone on wood opaque film forming coating failures. As moisture is sorbed into the wood structure, the wood swells in proportion to the volume of water sorbed. As moisture is lost, the wood shrinks in proportion to the volume of the water lost. Moisture in the wood end grain is responsible for coating failure in, for example, window corners and end to end siding. The wood cell wall moisture can be greatly reduced by a process known as acetylation which not only reduces the moisture sorbed in the cell wall but results in high levels of dimensional stability. The reduced moisture uptake along with the stability results in less stress created between the coating wood surface interface improving the performance of the coating and increasing its useful lifetime. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessReview
The Search for Durable Exterior Clear Coatings for Wood
Coatings 2015, 5(4), 830-864; https://doi.org/10.3390/coatings5040830 - 12 Nov 2015
Cited by 28
Abstract
The goal of a durable exterior clear coating has eluded generations of coatings technologists, despite long-standing desire amongst the public for such a coating. The journey towards this goal initially focused on modifications to coating formulation, but took a completely different direction when [...] Read more.
The goal of a durable exterior clear coating has eluded generations of coatings technologists, despite long-standing desire amongst the public for such a coating. The journey towards this goal initially focused on modifications to coating formulation, but took a completely different direction when it was found that a UV-transparent silicone clear coating on wood modified with chromic acid met consumer expectations of coating durability. This finding sparked world-wide interest in wood pre-treatments as a way of enhancing the durability of clear coatings. This interest initially focused on transition metal compounds, but has now shifted in the direction of organic and inorganic photostabilizers or even more drastic pre-treatments. Pre-treatments that dimensionally stabilize wood, protect it from microbial degradation and photostabilize lignin, when combined with flexible, photostable, coatings provide the next way-stop on the journey towards achieving the goal of durable exterior clear coatings for wood. This paper reviews this journey, drawing upon our research and that of other groups who have focused on this elusive goal. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessReview
Coating Acetylated Wood
Coatings 2015, 5(4), 792-801; https://doi.org/10.3390/coatings5040792 - 06 Nov 2015
Cited by 9
Abstract
Wood exposed to the outdoor environment is susceptible to weathering due to a series of chemical, biological and physical processes. Acetylation of wood is known to reduce cell wall moisture content, improve dimensional stability and durability against fungal decay. As a result of [...] Read more.
Wood exposed to the outdoor environment is susceptible to weathering due to a series of chemical, biological and physical processes. Acetylation of wood is known to reduce cell wall moisture content, improve dimensional stability and durability against fungal decay. As a result of these improvements, less stress is created between the coating and the wood surface improving the performance of the coating and increasing its useful lifetime. This paper is a review of research done on the chemistry of the acetylation process, the coating performance of acetylated wood and concentrates on the factors influencing coating performance. Full article
(This article belongs to the Special Issue Wood Coatings)
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