Research

12 pages, 1651 KiB

Open AccessCommunication

A Comparison of the Performance of Two Kinds of Waterborne Coatings on Bamboo and Bamboo Scrimber

by Jianfeng Xu, Ru Liu, Huagui Wu, Hongyun Qiu, Yanglun Yu, Ling Long and Yonghao Ni

Coatings 2019, 9(3), 161; https://doi.org/10.3390/coatings9030161 - 01 Mar 2019

Cited by 12 | Viewed by 3786

For this paper, two kinds of waterborne coatings, polyurethane acrylate (PUA) and epoxy resin, were synthesized and then coated onto neat bamboo and bamboo scrimber (BS), respectively. The coating performance of the samples was investigated. The results showed that, for the two kinds [...] Read more.

For this paper, two kinds of waterborne coatings, polyurethane acrylate (PUA) and epoxy resin, were synthesized and then coated onto neat bamboo and bamboo scrimber (BS), respectively. The coating performance of the samples was investigated. The results showed that, for the two kinds of coatings, there was a chemical reaction occurring between both coatings and the substrates. The permeability with respect to bamboo was higher than that of BS, while that of the epoxy resin coating was better than PUA. However, the PUA film was smoother than epoxy resin. The epoxy resin coating on bamboo had the best adhesion, which was at a 1 level. The abrasion values of the four samples varied in the same substrate. A higher hardness of the coating film was obtained when coated with PUA. In general, the coating performance of bamboo scrimber was poorer than that of bamboo, either coated with PUA or epoxy resin. The epoxy resin had a better coating performance than PUA. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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16 pages, 2791 KiB

Open AccessArticle

Method of Stabilizing Heavily Spalted Big Leaf Maple as a Decorative Coating Veneer Layer for Engineered Wood Flooring

by Diego Rodrigues de Oliveira, Claudia C. Andersen, Sarath M. Vega Gutierrez, Frederick A. Kamke and Seri C. Robinson

Coatings 2019, 9(2), 132; https://doi.org/10.3390/coatings9020132 - 19 Feb 2019

Cited by 4 | Viewed by 3154

Abstract

Spalted wood, wood colored by fungi, has been popular in woodcraft for centuries. Most spalted wood, however, is found in an advanced state of decay and cannot be utilized. This project describes the use of viscoelastic thermal compression (VTC) to investigate the potential [...] Read more.

Spalted wood, wood colored by fungi, has been popular in woodcraft for centuries. Most spalted wood, however, is found in an advanced state of decay and cannot be utilized. This project describes the use of viscoelastic thermal compression (VTC) to investigate the potential increase in spalted woods’ strength and stiffness, with the main objective of converting so-called “punky” wood into the top layer (veneer layer or “coating”) on commercial flooring. Spalted Acer macrophyllum logs were cut into veneers of size 7 mm × 7.8 cm × 25 cm and were then VTC-treated at 150 °C and 50 psi for 11.5 min. Statistical analysis on the mixed linear models showed significant increases for both the density and hardness of spalted wood (p < 0.0001). Density and Brinell hardness increased by 84% and 209%, respectively. FTIR analysis revealed that the wood polymers present in spalted wood were more susceptible to degradation imposed by the heat of the VTC treatment compared to sound wood. Additionally, the color analysis of the wood specimens showed statistically significant changes in color after the VTC treatment (p < 0.0001), which turned the wood surface darker and redder. The use of the VTC technology to transform spalted wood into wood flooring is viable. However, when exposed to moisture, the VTC-treated spalted wood showed a high percentage of set recovery (78%), which was significantly different from the set recovery of the sound wood (71%, p = 0.004). Successful use of VTC-treated spalted wood for flooring will require addressing of the swelling issue, and additional studies are needed to fully characterize the anatomy of VTC-treated spalted wood. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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13 pages, 1790 KiB

Open AccessArticle

Evaluation of the Impacts of Four Weathering Methods on Two Acrylic Paints: Showcasing Distinctions and Particularities

by Antoine Cogulet, Pierre Blanchet and Véronic Landry

Coatings 2019, 9(2), 121; https://doi.org/10.3390/coatings9020121 - 15 Feb 2019

Cited by 24 | Viewed by 4300

Abstract

Two commercial waterborne wood acrylic paints were applied to wood samples and the weathering resistance of samples was tested using four different weathering methods: outdoor exposure in Arizona (USA), Florida (USA), and the province of Quebec (Canada), and accelerated weathering in a QUV [...] Read more.

Two commercial waterborne wood acrylic paints were applied to wood samples and the weathering resistance of samples was tested using four different weathering methods: outdoor exposure in Arizona (USA), Florida (USA), and the province of Quebec (Canada), and accelerated weathering in a QUV (fluorescent) weatherometer. Degradation was characterised by colorimetric and FTIR analyses. FTIR confirmed the importance of paint composition in the resistance of samples to weathering. Polymer sensitivity to UV radiation was clearly evident. An interpretation of discoloration in terms of either the energy received by the samples or the length of exposure is presented. Strong differences existed between the four weathering methods. Particularities of each method are discussed and recommendations regarding their application for effective testing are proposed. Overall, in addition to accelerated weathering tests, we conclude that it is necessary to test paints in an end-use environment for accurate assessment of their likely performance. This study confirms the multifactorial aspect of the weathering process. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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16 pages, 3277 KiB

Open AccessArticle

Durability of Selected Transparent and Semi-Transparent Coatings on Siberian and European Larch during Artificial Weathering

by Kristýna Šimůnková, Eliška Oberhofnerová, Ladislav Reinprecht, Miloš Pánek, Milan Podlena and Irena Štěrbová

Coatings 2019, 9(1), 39; https://doi.org/10.3390/coatings9010039 - 14 Jan 2019

Cited by 6 | Viewed by 3304

Abstract

This paper compares the resistance of 20 commercial transparent and semi-transparent coatings applied to European and Siberian larch during artificial weathering in Xenotest. The change in gloss, colour, contact angle of wetting, resistance to Aspergillus niger and Penicillium brevicompactum moulds was evaluated, and [...] Read more.

This paper compares the resistance of 20 commercial transparent and semi-transparent coatings applied to European and Siberian larch during artificial weathering in Xenotest. The change in gloss, colour, contact angle of wetting, resistance to Aspergillus niger and Penicillium brevicompactum moulds was evaluated, and visual changes at the top surface of treated wood species were measured. Overall, the durability of coatings on European larch was higher than that on Siberian larch. The most durable of the tested coatings was a thin-film, i.e., semi-transparent oil-based film containing TiO₂ pigment and propiconazole fungicide. Of the transparent coatings, the most stable was a thick acrylic coating. Conversely, penetrating transparent oil systems had low colour stability and overall lifespan. Artificial weathering of all of the coatings resulted in a marked decrease in their resistance to moulds. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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14 pages, 5727 KiB

Open AccessArticle

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

by Laurence Podgorski, Céline Reynaud and Mathilde Montibus

Coatings 2019, 9(1), 27; https://doi.org/10.3390/coatings9010027 - 04 Jan 2019

Cited by 4 | Viewed by 3597

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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10 pages, 4415 KiB

Open AccessArticle

Fabrication of Hydrophobic ZnO/PMHS Coatings on Bamboo Surfaces: The Synergistic Effect of ZnO and PMHS on Anti-Mildew Properties

by Jingbing Chen, Yunyun Ma, Huiping Lin, Qingzhu Zheng, Xinxiang Zhang, Wenbin Yang and Ran Li

Coatings 2019, 9(1), 15; https://doi.org/10.3390/coatings9010015 - 28 Dec 2018

Cited by 26 | Viewed by 4403

Abstract

Poor mildew resistance has limited the application of bamboo materials. In this work, ZnO/PMHS coatings were fabricated on bamboo timber surfaces by hydrothermal synthesis method and hydrophobic modification with poly(methylhydrogen)siloxane (PMHS). The surface chemical characteristics and microstructure of the bamboo before and after [...] Read more.

Poor mildew resistance has limited the application of bamboo materials. In this work, ZnO/PMHS coatings were fabricated on bamboo timber surfaces by hydrothermal synthesis method and hydrophobic modification with poly(methylhydrogen)siloxane (PMHS). The surface chemical characteristics and microstructure of the bamboo before and after modification were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and water contact angle (WCA). The morphology results indicated that ZnO on the surface of bamboo forms flower-like aggregations. The WCA of ZnO/bamboo increased from 65° to 142° after PMHS hydrophobic modification, indicating that the hydrophobicity of bamboo was significantly improved. The original bamboo had poor anti-mildew properties when exposed to Trichoderma viride, Aspergillus niger, and Penicillium citrinum. After depositing ZnO onto the surface of the bamboo, the anti-mildew properties were significantly improved. Furthermore, it was found that after PMHS hydrophobic modification, ZnO/bamboo had excellent anti-mildew properties when exposed to the three mold hyphae, which indicated that PMHS hydrophobic modification had a synergistic effect on the anti-mildew properties of bamboo with a ZnO coating. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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12 pages, 1533 KiB

Open AccessArticle

Manufacture and Characteristics of Oil-Modified Refined Lacquer for Wood Coatings

by Chia-Wei Chang, Hsiu-Ling Lee and Kun-Tsung Lu

Coatings 2019, 9(1), 11; https://doi.org/10.3390/coatings9010011 - 26 Dec 2018

Cited by 23 | Viewed by 4270

Abstract

Oriental lacquer, a natural and renewable polymeric coating, comes from the sap produced by lacquer trees. For practical applications, oriental lacquer must be refined to reduce its water content and enhance its quality. In this study, drying oils were blended with oriental lacquer [...] Read more.

Oriental lacquer, a natural and renewable polymeric coating, comes from the sap produced by lacquer trees. For practical applications, oriental lacquer must be refined to reduce its water content and enhance its quality. In this study, drying oils were blended with oriental lacquer during a refining process to produce oil-modified refined lacquer (OMRL). Rhus succedanea lacquer, composed of 54.1% urushiols, 34.3% water, 7.2% plant gum, and 4.4% nitrogenous compounds, and drying oils, including tung oil (TO), linseed oil (LO), and dehydrated castor oil (DCO), were used as materials in this study. The effect of type and amount (0%, 10%, and 20% by wt %) of drying oils added to lacquer on lacquer properties were evaluated. Results show that the drying oils acted as a diluent, which reduced the viscosity, and enhanced workability, shortened touch-free drying time and accelerated the hardened drying of the OMRL. The results also indicated that the hardness, mass retention, T_g, tensile strength, abrasion resistance, and lightfastness of OMRL films decreased as more drying oils were blended with lacquer. Conversely, the bending resistance, elongation at break, impact resistance increased. Gloss was greatly improved through the blending of more drying oils with lacquer. In conclusion, the LO-modified refined lacquer (RL) had the highest film gloss and the DCO-modified RL had the shortest drying time for coating. Otherwise, the film properties were similar among the three types of drying oils. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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14 pages, 5155 KiB

Open AccessFeature PaperArticle

Plasma Pre-treatments to Improve the Weather Resistance of Polyurethane Coatings on Black Spruce Wood

by Jonathan G. Haase, Lukie H. Leung and Philip D. Evans

Coatings 2019, 9(1), 8; https://doi.org/10.3390/coatings9010008 - 25 Dec 2018

Cited by 19 | Viewed by 4755

Abstract

We hypothesize that plasma treatments that increase the adhesion and penetration of transparent water, and solvent-borne polyurethane coatings into black spruce wood will improve the performance of coated wood exposed to accelerated weathering. We tested this hypothesis by modifying wood samples with plasma [...] Read more.

We hypothesize that plasma treatments that increase the adhesion and penetration of transparent water, and solvent-borne polyurethane coatings into black spruce wood will improve the performance of coated wood exposed to accelerated weathering. We tested this hypothesis by modifying wood samples with plasma for 30, 180, 600, and 1200 s, and measuring coating penetration and adhesion using light microscopy and a mechanical pull-off test, respectively. Plasma treatment did not improve coating adhesion, but the solvent-borne coating showed deeper penetration into plasma-modified wood, and its resistance to accelerated weathering was better on plasma-modified wood than on untreated controls. Plasma treatments enhanced the penetration of water-borne polyurethane into wood, but the treatments did not improve weather-resistance of the coating. Plasma treatment increased the wettability of wood surfaces, and prolonged plasma treatment etched cell walls, increasing their porosity. These effects may explain the positive effect of plasma treatment on coating penetration, and the increased weather-resistance of the solvent-borne polyurethane on plasma-modified wood. In conclusion, our results indicate that the ability of plasma treatment to improve coating performance on black spruce depends on the coating type, and the effects of the treatment on the surface microstructure of wood. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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12 pages, 5572 KiB

Open AccessArticle

Efficient Antifungal and Flame-Retardant Properties of ZnO-TiO₂-Layered Double-Nanostructures Coated on Bamboo Substrate

by Danjing Ren, Jingpeng Li, Jun Xu, Zaixing Wu, Yongjie Bao, Neng Li and Yuhe Chen

Coatings 2018, 8(10), 341; https://doi.org/10.3390/coatings8100341 - 26 Sep 2018

Cited by 28 | Viewed by 3096

Abstract

A facile method to synthesize ZnO-TiO₂-layered double-nanostructures with the average thickness of 20 μm on a bamboo substrate was proposed to improve the antifungal and flame-retardant properties. The cross-linked wurtzite ZnO nanostructures with an average thickness of approximately 0.14 μm were [...] Read more.

A facile method to synthesize ZnO-TiO₂-layered double-nanostructures with the average thickness of 20 μm on a bamboo substrate was proposed to improve the antifungal and flame-retardant properties. The cross-linked wurtzite ZnO nanostructures with an average thickness of approximately 0.14 μm were uniformly distributed on the anatase TiO₂ surface. The energy-dispersive X-ray spectroscopy (EDS) confirmed that the ZnO-TiO₂ coating on bamboo was a layered double nanostructure. During a two-month antifungal test conducted in an outdoor environment, the fungi began to grow after one week on pristine bamboo and three weeks on ZnO-bamboo and TiO₂-bamboo. Furthermore, there was an infected area of 100% after four weeks for pristine bamboo and six weeks for ZnO-bamboo, while there was an infected area of 43% after eight weeks for TiO₂-bamboo. By comparison, there was no visible fungal growth on ZnO-TiO₂-bamboo until the end of the test. The electron spin resonance (ESR) technique has demonstrated that the reactive oxygen species (ROS) of •O₂⁻ and •OH were produced from the ZnO-TiO₂ surface under visible light irradiation (λ > 420 nm). This large quantity of •O₂⁻ compared to •OH is considered to be mainly responsible for the inactivation of fungi. Additionally, the limiting oxygen index has increased from 25.6% to 30.2% after being covered with a ZnO-TiO₂ coating, which revealed a significant enhancement of its flame-retardant property. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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14 pages, 5770 KiB

Open AccessArticle

Effect of Adding UV Absorbers Embedded in Carbonate Calcium Templates Covered with Light Responsive Polymer into a Clear Wood Coating

by Caroline Queant, Pierre Blanchet, Véronic Landry and Diane Schorr

Coatings 2018, 8(8), 265; https://doi.org/10.3390/coatings8080265 - 28 Jul 2018

Cited by 9 | Viewed by 6380

Abstract

The limited durability of clear coatings is a major issue for the coating and wood industry. The addition of organic UV absorbers improves coating resistance by the absorption and the conversion of the UV radiation into harmless heat. Organic UVAs are prone to [...] Read more.

The limited durability of clear coatings is a major issue for the coating and wood industry. The addition of organic UV absorbers improves coating resistance by the absorption and the conversion of the UV radiation into harmless heat. Organic UVAs are prone to degradation and can migrate in the binder of coatings. In this study, commercial UVAs and HALS have been entrapped into CaCO₃ templates coated with stimuli responsive polymers. Microspheres were incorporated into a clear acrylic water-based coating formulation. The formulation was applied on glass and wood panels and was placed into an artificial UV chamber. This study presents a comparison between the aesthetic behavior of coating formulations with free and encapsulated commercial UVAs and HALS during the accelerated ageing test. Encapsulation of UVAs was confirmed by XPS and TGA analysis. Results have shown that the coating’s aesthetic was slightly improved when using the encapsulated products. Full article

(This article belongs to the Special Issue Additives and Pre-treatments to Enhance the Performance of Coatings on Wood)

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