Surface Properties and Surface Treatments of Wood and Wood-Based Composites

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Surface Characterization, Deposition and Modification".

Deadline for manuscript submissions: 20 September 2024 | Viewed by 27659

Special Issue Editor


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Guest Editor
Department of Wood Science & Technology, Biotechnical faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
Interests: wood coatings for interior and exterior; interactions of wood coatings with various substrates (wood, modified wood, densified wood); wood liquefaction and preparation of new wood coatings on the basis of liquefied wood; applications of nanomaterials in wood coatings and in treatment of wood; surface properties of wood and lignocellulosic materials

Special Issue Information

Dear Colleagues,

Whenever products made of wood or wood-based composites are utilized, when their weathering is studied, or when the processes of wood deterioration due to exposure to biotic or abiotic factors are investigated, it is the surface of the object under consideration that must be taken into account at first. Therefore, surface properties of wood have to be known well and tailored to the purpose. Proper surface characterization and treatment methods must be selected to get the most relevant surface properties. Some surface treatment process are well established, like surface finishing of wood with coatings, and others are less known, and their potentials are underestimated. Just to illustrate, this is also the case with plasma treatments, which have been utilized for decades, but the potentials of this technique for treatment of wood and wood-based composites would deserve larger attention, both from a research as well as from an industrial exploitation point of view.

This Special Issue will serve as a forum for papers in the following concepts:

  • Surface finishing of wood and wood-based composites with all kinds of stains and film-forming coatings to obtain a fit-for-purpose finished product;
  • Properties of wood surface systems, including resistance to weathering and biological deterioration parameters;
  • Plasma treatments;
  • Functionalization of lignocellulosic material surfaces, e.g., by grafting, sol–gel treatments, deposition of nanoparticles;
  • Surface-free energy of lignocellulosic materials, either untreated or finished;
  • Wettability of wood and wood-based materials and their treated surfaces;
  • Microscopic and spectroscopic surface analytical methods;
  • Adsorption phenomena on untreated and surface finished lignocellulosic materials.

Prof. Dr. Marko Petric
Guest Editor

Manuscript Submission Information

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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.

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Keywords

  • Protective and decorative wood finishes
  • Surface properties of wood and wood-based materials
  • Plasma treatments
  • Functionalization, grafting, sol–gel, nanoparticles

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Published Papers (9 papers)

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Research

17 pages, 21836 KiB  
Article
Effect of Two Types of Pomelo Peel Flavonoid Microcapsules on the Performance of Water-Based Coatings on the Surface of Fiberboard
by Jinzhe Deng, Tingting Ding and Xiaoxing Yan
Coatings 2024, 14(8), 1032; https://doi.org/10.3390/coatings14081032 - 14 Aug 2024
Viewed by 293
Abstract
In order to achieve antibacterial properties in water-based coatings, two types of antibacterial pomelo peel flavonoid microcapsules were added to water-based coatings and decorated on the surface of fiberboard. The surface coatings of the substrates were tested and analyzed. The antibacterial rate of [...] Read more.
In order to achieve antibacterial properties in water-based coatings, two types of antibacterial pomelo peel flavonoid microcapsules were added to water-based coatings and decorated on the surface of fiberboard. The surface coatings of the substrates were tested and analyzed. The antibacterial rate of the surface coatings of the two groups of fiberboards gradually increased with the increase in the content of the microcapsules. The color difference of the surface coatings of both groups increased slightly, the glossiness decreased, the gloss loss rate increased greatly, and the reflectivity increased slightly. The adhesion of the surface coatings of the two groups of fiberboards did not change significantly, the roughness gradually increased, the hardness of the melamine-resin-coated pomelo peel flavonoid microcapsules gradually increased, and the impact resistance slightly improved. Compared with the antibacterial results of the coating without substrate at the same content, the antibacterial effect of the fiberboard surface coating was slightly decreased. Overall, the surface coating on the fiberboard with 9.0% chitosan-coated pomelo peel flavonoid microcapsules demonstrated superior performance, superior coating morphology, and enhanced antibacterial properties. The antibacterial rate was 73.7% against Escherichia coli, and the antibacterial rate was 77.4% against Staphylococcus aureus. The color difference was 3.85, the gloss loss rate was 90.0%, and the reflectivity was 20.19%. The hardness was HB, the adhesion was level 1, the impact resistance level was 3, and the roughness was 1.94 μm. This study explored the effect of antibacterial microcapsules on coating performance, providing a technical basis for the application of the antibacterial microcapsules. Full article
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21 pages, 6772 KiB  
Article
The Effects of Urea–Formaldehyde Resin-Coated Toddalia asiatica (L.) Lam Extract Microcapsules on the Properties of Surface Coatings for Poplar Wood
by Ye Zhu, Ying Wang and Xiaoxing Yan
Coatings 2024, 14(8), 1011; https://doi.org/10.3390/coatings14081011 - 9 Aug 2024
Viewed by 394
Abstract
Urea–formaldehyde resin was used as a wall material and Toddalia asiatica (L.) Lam extract was used as a core material to prepare urea–formaldehyde resin-coated Toddalia asiatica (L.) Lam extract microcapsules (UFRCTEMs). The effects of UFRCTEM content and the mass ratio of core-to-wall material [...] Read more.
Urea–formaldehyde resin was used as a wall material and Toddalia asiatica (L.) Lam extract was used as a core material to prepare urea–formaldehyde resin-coated Toddalia asiatica (L.) Lam extract microcapsules (UFRCTEMs). The effects of UFRCTEM content and the mass ratio of core-to-wall material (Mcore:Mwall) on the performance of waterborne coatings on poplar surfaces were investigated by adding microcapsules to the waterborne topcoat. Under different Mcore:Mwall of microcapsules, as the content of microcapsules increased, the glossiness and adhesion of the coatings gradually decreased, and the color difference value of the coatings gradually increased. The cold liquid resistance, hardness, and impact resistance of the coatings were all improved, and the roughness of the coatings increased. The antibacterial rates of the coatings against Escherichia coli and Staphylococcus aureus were both on the rise, and the antibacterial rate against Staphylococcus aureus was slightly higher than that against Escherichia coli. When the microcapsule content was 7.0% and the Mcore:Mwall was 0.8:1, the surface coating performance on poplar wood was excellent. The glossiness was 3.43 GU, light loss was 75.55%, color difference ΔE was 3.23, hardness was 2H, impact resistance level was 3, adhesion level was 1, and roughness was 3.759 µm. The cold liquid resistance was excellent, and resistance grades to citric acid, ethanol, and cleaning agents were all 1. The antibacterial rates against Escherichia coli and Staphylococcus aureus were 68.59% and 75.27%, respectively. Full article
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21 pages, 5920 KiB  
Article
Preparation and Characterisation of UV-Curable Flame Retardant Wood Coating Containing a Phosphorus Acrylate Monomer
by Solène Pellerin, Fabienne Samyn, Sophie Duquesne and Véronic Landry
Coatings 2022, 12(12), 1850; https://doi.org/10.3390/coatings12121850 - 29 Nov 2022
Cited by 5 | Viewed by 2471
Abstract
The application of a flame retardant coating is an effective solution to enhance the fire retardancy of wood flooring. However, finding the right balance between reducing the flame propagation and good overall coating properties while conserving wood appearance is complex. In order to [...] Read more.
The application of a flame retardant coating is an effective solution to enhance the fire retardancy of wood flooring. However, finding the right balance between reducing the flame propagation and good overall coating properties while conserving wood appearance is complex. In order to answer this complex problem, transparent ultraviolet (UV)-curable flame retardant wood coatings were prepared from an acrylate oligomer, an acrylate monomer, and the addition of the tri(acryloyloxyethyl) phosphate (TAEP), a phosphorus-based monomer, at different concentrations in the formulation. The coatings’ photopolymerisation, optical transparency, hardness, water sorption and thermal stability were assessed. The fire behaviour and the adhesion of the coatings applied on the yellow birch panels were evaluated, respectively, using the cone calorimeter and pull-off tests. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses were performed on the collected burnt residues to obtain a better understanding of the flame retardancy mechanism. Our study reveals that phosphorus monomer addition improved the coating adhesion and the fire performance of the coated wood without impacting the photopolymerisation. The conversion percentage remained close to 70% with the TAEP addition. The pull-off strength reached 1.12 MPa for the coating with the highest P-monomer content, a value significantly different from the non-flame retarded coating. For the same coating formulation, the peak of heat release rate decreased by 13% and the mass percentage of the residues increased by 37% compared to the reference. However, the flame-retarded coatings displayed a higher hygroscopy. The action in the condensed phase of the phosphorus flame retardant is highlighted in this study. Full article
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17 pages, 13825 KiB  
Article
Quality of Oil- and Wax-Based Surface Finishes on Thermally Modified Oak Wood
by Zuzana Vidholdová, Gabriela Slabejová and Mária Šmidriaková
Coatings 2021, 11(2), 143; https://doi.org/10.3390/coatings11020143 - 28 Jan 2021
Cited by 17 | Viewed by 4122
Abstract
In this study, natural linseed oil, hard wax oil, and hard wax, commonly used as finishes for wooden furniture and parquet, were used for surface finishes on Turkey oak wood (Quercus cerris L.), thermally modified at temperatures of 175 °C and 195 [...] Read more.
In this study, natural linseed oil, hard wax oil, and hard wax, commonly used as finishes for wooden furniture and parquet, were used for surface finishes on Turkey oak wood (Quercus cerris L.), thermally modified at temperatures of 175 °C and 195 °C for 4 h. Several resistance surface properties were investigated. The mechanical resistance properties of all surface finishes were very much allied to interactions between the finish and the type of substrate. The adhesion strength and impact resistance decreased if higher temperature was used for thermal modification of the substrate. The surface hardness and the resistance to abrasion were high and increased slightly with increasing temperature during thermal modification of wood. It was also found that surface adhesion, hardness and resistance to impact were very much related to interactions between the coating film and the substrate. The resistance properties of finishes, such as resistance to cold liquids and mold, were mainly influenced by the type of the surface finish. The resistance to cold liquids increased in the order: surface finish with hard wax < linseed oil < finish system of linseed oil + hard wax oil. The lowest resistance to cold liquids showed up in condensed milk and sanitizer. Resistance to Aspergillus niger and Penicillium purpurogenum was relatively weak, however apparently improved during the first 7 days of the fungal test; the surfaces were covered with a lower distribution density of fungal mycelium after 21 days of the fungal test. Individual surface performances of oil and wax-based surface finishes on native wood were different from thermally modified wood. Full article
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13 pages, 3045 KiB  
Article
Superhydrophilic Coating of Pine Wood by Plasma Functionalization of Self-Assembled Polystyrene Spheres
by Sebastian Dahle, John Meuthen, René Gustus, Alexandra Prowald, Wolfgang Viöl and Wolfgang Maus-Friedrichs
Coatings 2021, 11(2), 114; https://doi.org/10.3390/coatings11020114 - 20 Jan 2021
Cited by 6 | Viewed by 2835
Abstract
Self-assembling films typically used for colloidal lithography have been applied to pine wood substrates to change the surface wettability. Therefore, monodisperse polystyrene (PS) spheres have been deposited onto a rough pine wood substrate via dip coating. The resulting PS sphere film resembled a [...] Read more.
Self-assembling films typically used for colloidal lithography have been applied to pine wood substrates to change the surface wettability. Therefore, monodisperse polystyrene (PS) spheres have been deposited onto a rough pine wood substrate via dip coating. The resulting PS sphere film resembled a polycrystalline face centered cubic (FCC)-like structure with typical domain sizes of 5–15 single spheres. This self-assembled coating was further functionalized via an O2 plasma. This plasma treatment strongly influenced the particle sizes in the outermost layer, and hydroxyl as well as carbonyl groups were introduced to the PS spheres’ surfaces, thus generating a superhydrophilic behavior. Full article
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13 pages, 622 KiB  
Article
Interactions of Coating and Wood Flooring Surface System Properties
by Matjaž Pavlič, Marko Petrič and Jure Žigon
Coatings 2021, 11(1), 91; https://doi.org/10.3390/coatings11010091 - 15 Jan 2021
Cited by 22 | Viewed by 3372
Abstract
Parquet flooring is one of the most common types of flooring, the surface of which can be covered with various coatings. To avoid possible damage to the parquet during use, it is necessary to test the surfaces before installation according to various non-standard [...] Read more.
Parquet flooring is one of the most common types of flooring, the surface of which can be covered with various coatings. To avoid possible damage to the parquet during use, it is necessary to test the surfaces before installation according to various non-standard and standard protocols. The present study provides an overview of the interactions between the properties of selected waterborne coatings (solids content, hardness, resistance to cracking, tensile strength) and the properties of oak wood flooring surfaces (dry film thickness, coating adhesion, resistance to scratching, impact, abrasion and cold liquids). The tests conducted showed that the performance of the surface systems was highly dependent on the coating formulations, as they were either one- or two-component systems. Although no major differences in surface resistance to cold liquids were found, there was a correlation between coating thickness, hardness and tensile strength. The harder coatings had higher tensile strengths and lower elongations. The coatings with higher tensile strength and better hardness achieved better adhesion properties. The coatings that exhibited ductile behavior showed the worst scratch resistance. A statistically significant relationship was found between the higher resistance of the flooring systems to impact stress and the improved abrasion resistance. The obtained results provide potential end users of surface coatings with valuable information on the quality that can be expected in wood flooring. Full article
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13 pages, 1857 KiB  
Article
Enhancing Thermally Modified Wood Stability against Discoloration
by Dace Cirule, Errj Sansonetti, Ingeborga Andersone, Edgars Kuka and Bruno Andersons
Coatings 2021, 11(1), 81; https://doi.org/10.3390/coatings11010081 - 13 Jan 2021
Cited by 15 | Viewed by 3468
Abstract
Thermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood [...] Read more.
Thermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood was assessed and, based on these results, the possibility to delay discoloration due to weathering by non-film forming coating containing transparent iron oxides in the formulation was studied. The effect of including organic light stabilizers (UVA and HALS) in coatings as well as pretreatment with lignin stabilizer (HALS) was evaluated. Artificial and outdoor weathering was used for testing the efficiency of different coating formulations on TM wood discoloration. For color measurements and discoloration assessment, the CIELAB color model was used. Significant differences between the spectral sensitivity of unmodified and TM wood was observed by implying that different strategies could be effective for their photostabilization. From the studied concepts, the inclusion of the transparent red iron oxide into the base formulation of the non-film forming coating was found to be the most effective approach for enhancing TM wood photostability against discoloration due to weathering. Full article
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15 pages, 3329 KiB  
Article
Study of the Adhesion of Silicate-Based Coating Formulations on a Wood Substrate
by Arnaud Maxime Cheumani Yona, Jure Žigon, Sebastian Dahle and Marko Petrič
Coatings 2021, 11(1), 61; https://doi.org/10.3390/coatings11010061 - 7 Jan 2021
Cited by 14 | Viewed by 4802
Abstract
Silicate coatings are environmentally friendly inorganic-based products that have long been used for mineral substrates and protection of steel against corrosion. The development and acceptance of these coatings in the wood sector require some adjustments in formulations or special preparation of the surface [...] Read more.
Silicate coatings are environmentally friendly inorganic-based products that have long been used for mineral substrates and protection of steel against corrosion. The development and acceptance of these coatings in the wood sector require some adjustments in formulations or special preparation of the surface to be coated to obtain durable finishes. In this work, the adhesion of various silicate-based formulations to a beech wood substrate (Fagus sylvatica L.), was assessed with the main objective to study relevant parameters and potential improvements. Adhesion strength was determined by pull-off and cross-cut tests. Other coating properties such as scratch, impact, and water resistance were also determined. Surface roughness and interface were analyzed using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM), and coating curing was studied by attenuated total reflection-infrared spectroscopy (ATR FTIR). The results showed that adhesion was highly dependent on formulation, penetration of the coatings into wood, and mechanical anchoring. Increasing the content of solid particles in the coating formulations or adding a polyol (glycerol, xylose), which probably acted as a coalescent, considerably decreased the adhesion strength, probably by blocking penetration into the wood by forming aggregates. Adhesion was improved by pre-mineralization of the surface, and substitution of a part of the potassium silicate binder with potassium methyl siliconate reduced the formation of cracks caused by dimensional instability of the wood. Full article
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12 pages, 3661 KiB  
Article
Fire Characteristics of Selected Tropical Woods without and with Fire Retardant
by Linda Makovicka Osvaldova, Patricia Kadlicova and Jozef Rychly
Coatings 2020, 10(6), 527; https://doi.org/10.3390/coatings10060527 - 29 May 2020
Cited by 19 | Viewed by 3942
Abstract
The flammability of tropical woods and the effect of a selected fire protection coating were evaluated using a cone calorimeter at a cone radiancy of 35 kW/m2. Three samples were from the South American continent (Cumaru, Garapa, Ipe), and two were [...] Read more.
The flammability of tropical woods and the effect of a selected fire protection coating were evaluated using a cone calorimeter at a cone radiancy of 35 kW/m2. Three samples were from the South American continent (Cumaru, Garapa, Ipe), and two were from the Asian continent (Kempas and Merbau). Samples were treated with commercial fire retardant (FR) containing ferrous phosphate as an essential component. The untreated samples were used as reference materials that were of particular interest concerning their flammability. It was shown that there is unambiguous correlation between the effective heat of combustion (EHC) and total oxygen consumed (TOC) related to mass lost during burning for both the untreated and treated samples. In the case of Cumaru and Garapa, there exists an inverse relation between the amount of smoke and carbon residue. The decisive effect on the time of ignition was performed by the initial mass of the sample. This is valid for the spruce and the Cumaru, Ipe, and Kempas, both treated and untreated with retardant, while Garapa and Merbau were found to decline. According to the lower maximum average rate of heat emission (MARHE) parameter, a lower flammability was observed for the treated samples of wood, except for Garapa wood. Fire-retardant treated Garapa and Merbau also have a significantly lower time to ignition than untreated ones. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Interactions of coating and wood flooring surface system properties

Authors: Pavlič, M.; Petrič, M.; Žigon J.

 
 
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