Adhesion and thermal stability of thickness insensitive spectrally selective (TISS) polyurethane-based paint coatings on copper substrates (original) (raw)
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Solar Energy Materials and Solar Cells, 1995
Thickness-sensitive spectrally-selective (TSSS) paint coatings were prepared by using FeMnCuO x pigment in combinations with phenoxy and silicone resins. The spectral selectivity expressed as a ratio between solar absorptance (a s) and thermal emittance (e x) was 0.92/0.14 for the first and 0.87/0.18 for the second type of the paint. The surface of phenoxy resin based coatings is characterized by pigment particles protruding from the surface, while silicone based paints exhibit a much smoother surface. Abrasion resistance and adhesion of both types of coatings were enhanced by cross linking the resin binder with diisocyanate hardener. Cured coatings withstand temperatures up to 135°C. Cross-linking and degradation mechanisms of both types of coatings were studied by using FT-IR spectroscopy and thermogravimetric measurements, cycling and ageing tests.
The aesthetic demand has become an imperative challenge to advance the practical and commercial application of daytime radiative cooling technology toward mitigating climate change. Meanwhile, the application of radiative cooling materials usually focuses on the building surface, related tightly to fire safety. Herein, the absorption and reflection spectra of organic and inorganic colorants are first compared in solar waveband, finding that iron oxides have higher reflectivity in NIR region. Second, three kinds of iron oxides-based colorants are selected to combine porous structure and silicon-modified ammonium polyphosphate (Si-APP) to engineer colored polyurethane-based (PU) coating, thus enhancing the reflectivity and flame retardancy. Together with reflectivity of more than 90% in near-infrared waveband and infrared emissivity of ≈91%, average temperature drops of ≈5.7, ≈7.9, and ≈3.8°C are achieved in porous PU/Fe 2 O 3 /Si-APP, porous PU/Fe 2 O 3 •H 2 O/Si-APP, and porous PU/Fe 3 O 4 •H 2 O/Si-APP, compared with dense control samples. The catalysis effect of iron oxides in the cross-linking reaction of pyrolysis products and dehydration mechanism of Si-APP enable PU coating to produce an intumescent and protective char residue. Consequently, PU composite coatings demonstrate desirable fire safety. The ingenious choice of colorants effectively minimizes the solar heating effect and trades off the daytime radiative cooling and aesthetic appearance requirement.
Rheological Behavior of Spectrally Selective Coatings for Polymeric Solar Absorbers
Coatings, 2022
Since the world’s energy demands are growing rapidly, there is a constant need for new energy systems. One of the cleanest, most abundant, and renewable natural resources available is solar energy; therefore, the development of surfaces with high absorption of solar radiation is increasing. To achieve the best efficiency, such surfaces are coated with spectrally selective coatings, which are strongly influenced by the pigments and resin binders. Spectrally selective paints have a very specific formulation, and since the applied dry coatings should exhibit high spectral selectivity, i.e., high solar absorptivity and low thermal emissivity, the rheological properties of liquid paints are of great importance. In the present work, we studied the effect of the rheological properties of liquid thickness-insensitive spectrally selective (TISS) paints on the spectral selectivity and adhesion of dry coatings on a polymeric substrate. The results showed that the functional and adhesion proper...
Solar Energy - SOLAR ENERG, 2001
In this paper the preparation and testing of spectrally selective paint coatings for absorbers in flat-plate solar collectors are shown. This represents the most inexpensive way of preparing such an absorber. Basic properties of coatings prepared on aluminum, copper and stainless steel substrates are described together with the stability of the painted substrate. To calculate the performance of the solar collector with a painted absorber, a dynamic multi-node model was applied. It considers the main components and heat transfer fluxes of a flat-plate solar collector.
Solar Energy Materials and Solar Cells, 2012
Solar energy is the most abundant source of renewable energy. The direct method of harnessing solar energy is the solar thermal conversion method using solar absorbers. The absorbers are coated with solar selective coatings with high absorptance and low thermal emittance. Spectrally selective coatings which are stable up to temperatures ≤ 300°C (in air and vacuum) have been developed in the past. These coatings are mainly deposited from wet chemical routes (e.g., electrodeposition) and have been reviewed widely in the literature.
New Solar Selective Surface Coatings: A Review
International Journal of Latest Research in Engineering and Technology, 2017
An ideal solar selective surface coating must have good optical properties like high solar absorptance and minimum solar emittance. A new and affordable solar selective surface coating having higher solar absorption efficiency with low in-frared emittance compared to the commercial black paint coating used in most ordinary solar water heating systems has been developed. Such as solar selective coatings like black Nickel-Aluminium alloy particles with commercial black paint. Also, soalar selective surface coating with black nickel-cobalt plating on aluminium alloy substrates with nickel undercoat has been developed. Characterization study of such solar selective coatings is done in this paper. Characterization of coating includes Spectroscopic studies, Surface morphology and XRD studies, Polarization studies for corrosion resistance.
Chemical Degradation and Color Changes of Paint Protective Coatings Used in Solar Glass Mirrors
Coatings, 2021
This paper reports a study of the influence of outdoor natural aging on paint coatings applied to the back of three commercial solar glass mirrors (A1, C2, and D2) under two different exposure environments (marine and desert) in Morocco for a period of about three years. The aging assessment was carried out through colorimetric measurements and FTIR-ATR (Attenuated total reflection-Fourier transform infrared) analyses of the top coat paints. The obtained results demonstrate that the tested coating system had a high resistance at the desert site. Under the desert environment, no obvious changes to the coating occurred after 350 days. However, at the marine site, some color changes were detected, and the coating got yellow and more matte, especially for mirror A1. FTIR-ATR analyses have indicated many modifications in the intensity of many bonds of infrared spectra especially for paint of this mirror type (A1). This chemical degradation is not only due to UV degradation but also relat...
Heat insulation effect in solar radiation of polyurethane powder coating nanocomposite
2021
This study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the min...
Wet-chemistry based selective coatings for concentrating solar power
Spectrally selective coatings are common in low and medium temperature solar applications from solar water heating collectors to parabolic trough absorber tubes. They are also an essential element for high efficiency in higher temperature Concentrating Solar Power (CSP) systems. Selective coatings for CSP are usually prepared using advanced expensive methods such as sputtering and vapor deposition. In this work, coatings were prepared using low-cost wet-chemistry methods. Solutions based on Alumina and Silica sol gel were prepared and then dispersed with black spinel pigments. The black dispersions were applied by spray/roll coating methods on stainless steel plates. The spectral emissivity of sample coatings was measured in the temperature range between 200 and 500°C, while the spectral absorptivity was measured at room temperature and 500°C. Emissivity at wavelengths of 0.4-1.7 µm was evaluated indirectly using multiple measurements of directional reflectivity. Emissivity at wavelengths 2-14 µm was measured directly using a broadband IR camera that acquires the radiation emitted from the sample, and a range of spectral filters. Emissivity measurement results for a range of coated samples will be presented, and the impact of coating thickness, pigment loading, and surface preparation will be discussed.