Academic literature on the topic 'NIR reflective pigments'

Ca₂Mn_0.85Ti_0.15O₄ was synthesized as an inorganic black pigment with thermal barrier properties, and its NIR solar reflectance value was much greater than those of the conventional NIR reflective black pigments.

For building applications, coatings are needed in order to obtain an attractive appearance and protection against the outdoor environments. Buildings are responsible for consumption of cooling energy. Cool coatings applied over buildings surface provide an effective solution for passive cooling of building indoors and influencing local outdoor microclimate, mitigating urban heat islands effect (UHIE). Cool coatings have to resistant to weathering and ageing. For this reason, we developed near infrared (NIR) reflective pigments with the aim to add in binder and obtaining a cool coating. A series of pigments displaying YIn0.9Mn0.1O3–ZnO stoichiometry was synthesized by sol-gel route. The dried gel precursor was calcined at different temperatures for 2h (650°C, 800°C and 850°C) to observe the formation of a light brown pigment and two different blue shades. Precursors and calcined final pigments were characterized by using physicochemical analyses. The colour of pigments was studied using CIE-2004 L*a*b* colorimetric method. The cooling effect of pigments and their thermal stability were confirmed by NIR reflectance measurements and TGA respectively.

Linear-low-density-polyethylene- (LLDPE-) based formulations with several near-infrared- (NIR-) reflective pigments were prepared by melt blending technique and their subsequent films were prepared by blown film extrusion process. Thermal properties of these films were evaluated using differential scanning calorimetry (DSC). The results showed that the melting and crystallization temperatures (TmandTc, resp.) of these formulations were almost similar to that of control resin. The melt viscosity was measured by stress-controlled rotational rheometer and melt flow index (MFI) instruments. Rheological measurements indicated that the blend formulations with NIR-reflective additive have similar melt viscoelastic behavior (storage modulus and dynamic viscosity) to the control resin. The mechanical test performed on NIR-reflective films showed similar values of tensile strength for blend samples as that of control resin. The spectral radiometric properties of the blend films were evaluated in the solar wavelength range of 200–1100 nm and found to be improved over the control sample without having NIR-reflective pigment.

This research article reports a development on green pigments having high reflectance of NIR radiation from the sun. The aim of the development is to use the green pigments as a component of building paint to reduce heat penetrating into the building. Cr2O3, a green pigment oxide, was used as the host component and the mixtures of Al2O3, V2O5 and TiO2 were used as the guest components. Al2O3, V2O5 and TiO2 were mixed at different 36 compositions according to triaxial diagram. For each sample preparation, 80% wt Cr2O3 was mixed with 20%wt of guest component for each composition. Then the mixed sample were calcined at 1150 °C for 4 hours and were ground with an agate ball mill for 7 minutes at a speed of 250 rev/min. Finally, the pigments were sieved to obtain the particle sizes of 0.5 - 2.0 µm. The pigment powders were compressed in a mold to get samples in the form of thin disks, each one with a diameter of 2.7 cm and a thickness of 4 mm. The reflectance for all samples was measured using a spectrophotometer in the wavelength ranging from 300 – 2100 nm in accordance with ASTM E891. It was found that the maximum reflectance, in the wavelengths ranging from 780 – 2100 nm, of 82.83% was obtained from the sample with a composition of 80%Cr2O3, 14%Al2O3, 4%TiO2 and 2% V2O5.

Near-infrared (NIR) reflective materials are being developed for mitigating building cooling needs. Their use contributes to broadening the range of colours, responding to the urban aesthetic demand without compromising the building performance. Despite the increase in NIR reflective pigments investigation, there is still a knowledge gap in their applicability, impact, and durability in multilayer finishing coatings of External Thermal Insulation Composite Systems (ETICS). Hence, the main goal of this work consists of evaluating the impact of incorporating NIR reflective pigments (NRP) in the solar reflectance of the surface layer of ETICS, without affecting the colour perception, as well as their influence on the colour durability and surface temperature. As such, colour, solar reflectance, and surface temperature were monitored for 2 years in dark-coloured specimens of ETICS, with and without NRP and a primer layer. It was confirmed that the main contribution of NRP is the increase of solar reflectance and, consequently, the decrease in surface temperature, especially for high exterior temperatures (around 30 ºC). Moreover, these pigments highly increase the NIR reflectance without affecting the visible colour. In addition, they contribute to maintaining the colour characteristics. The application of primer increased the surface temperature, especially for higher exterior temperatures. However, it contributes to a lower colour difference and solar reflectance variation, which is an important achievement for durability purposes.

This work aimed to explore the possibility of producing NIR-reflective pigment from Thai leucoxene which is an abundant mineral consisting of ~89 wt.% TiO2, 6 wt.% SiO2 and 5 wt.% other oxides such as Al2O3 and Fe2O3. The leucoxene was purified by selective leaching of undesired oxides with NaOH under hydrothermal condition. Effects of NaOH concentration, hydrothermal temperature and time were investigated. The results revealed that dissolutions of the SiO2 and Al2O3 increased with an increased NaOH concentration, while that of the ZrO2 and Fe2O3 remained the same, resulting in the increased TiO2 concentration. The SiO2 dissolution also increased with an increased temperature and time. The optimum leaching condition, i.e. 4 M NaOH, 180 °C and 60 min, yielded TiO2 content of 93.94 ±0.14 wt.%. The Cr-doped CaTiO3 pigments (CaCrxTi1-xO3; x = 0, 0.025, 0.05, 0.75 and 0.1), synthesized from the purified leucoxene, CaO and Cr2O3 by solid-state reaction at 1100 °C, exhibited brown color hue and NIR reflectance in a range of 34.5−59.8% depending on the Cr content. At the Cr content of 0.05, the pigment exhibited decent brownish appearance and modest NIR reflectance of 50.7% which was close to that of the pigment synthesized from pure rutile. The glaze consisting of 10 wt.% pigment had a glossy light brown appearance, and possessed NIR reflectance of 75.0 %, indicating a promising application in a field of NIR-reflective coating.

Developing strategies for the green synthesis of novel materials, such as pigments for protection from solar radiation, is a fundamental research subject in material science to mitigate the heat island effect. Within this perspective, the current study reports on the synthesis of blue pigments of ZnAl2O4:M (M = Co2+ and Co2+/Nd3+) using recycled metallic aluminum (discarded can seal) with reflective properties of Near-infrared radiation. The pigments were characterized by XRD, SEM, XPS, UV-Vis, NIR diffuse reflectance spectroscopy, and CIE-1976 L*a*b* color measurements. The wettability of the coatings containing the synthesized pigments was also evaluated. The structural characterization showed that the pigments present the Gahnite crystalline phase. Colorimetric measurements obtained by the CIEL*a*b* method show values correlated to blue pigments attributed to Co2+ ions in tetrahedral sites. The pigments exhibit high near-infrared solar reflectance (with R% ≥ 60%), with an enhancement of nearly 20% for the pigment-containing neodymium when applied in white paint, indicating that the prepared compounds have the potential to be energy-saving color pigments for coatings.

This study aims to evaluate the difference in thermal behavior among paints with the presence of traditional and NIR pigments by means of a simple and cheap laboratory-scale test. Considering these goals, the thermal and esthetical properties of two different cool coatings were assessed, highlighting their positive and limited aspects. Two different complex near-infrared inorganic reflective (NIR) pigments with yellow and black respectably colors were mixed in an acrylic waterborne copolymer binder. The paint formulations were applied on steel panels. The thermal performance of the coatings was investigated in the NIR-region of the light spectrum by exposing the samples to an IR-lamp. The outer and inner surface temperatures of the painted panels were recorded using thermocouples and an IR camera. The samples were aged by artificial UV-B light exposure. Color and specular gloss changes at different exposure times were evaluated. The behavior of the cool coatings was compared with that of conventional coatings with similar color characteristics. The black cool coating achieved a maximum temperature decrease, compared to the conventional black one, of approximately 12 °C. The stability for the cool coatings was very similar to that of the conventional coating, indicating that black pigment could be a potential candidate for cool-coating applications. The yellow cool coatings did not show a significant decrease in temperature compared to the conventional paint. The gloss and color changes resulted as influenced by the types and amount of pigments.

The present thesis is devoted to synthesis, through the environmentally friendly citrate sol-gel route, of YIn0.9O3 −ZnO near infrared reflective based pigments, having different chromophore elements (Mn, Cu, Fe), with the aim to add in binder and obtaining cool coatings. A “cool” coating for roofing consists of paint (or glaze) containing color pigments, which do not absorb the infrared portion of the solar spectrum. Cool coatings applied over buildings surface provide an effective solution for passive cooling of building indoors and influencing local outdoor microclimate, mitigating urban heat islands effect (UHIE). The primary purpose is to produce pigments according to an environmentally friendly route, using non-toxic raw materials, as well as short times and low temperatures for synthesis, and without residual waste. The resulting pigments must have high reflectance in the near-infrared so that they can be used in the field of cold paints. To realize the corresponding coatings, pigments were dispersed in two different binders (standard PMMA and industrial binder). For the most interesting pigments, in terms of NIR reflectance, other property, was decided to explore, which define these NIR reflective pigments as smart pigments for building application: the photocatalytic ability.

碩士
國立宜蘭大學
化學工程與材料工程學系碩士班
99
This thesis consists of two different parts to investigate the chemical structure, microstructrue, thermal properties, mechanical properties and rheology of polymer blends. The first part is the study on PET (Polyethylene terephthalate)/HDPE (High density polyethylene)/NIR (Near infrared reflective pigment) ternary composites, EGMA-VA (Ethylene/glycidyl methacrylate/vinyl acetate) as compatibilizer. HDPE were pre-mixed with 25 wt% NIR form N-HDPE master batches. Then, variable amounts of N-HDPE were mixed with PET and EGMA-VA to prepare PET/N-HDPE/EGMA-VA composites. The result of FT-IR (Fourier transform IR spectroscopy) revealed reaction between the epoxy groups on EGMA and terminal carboxylic acid and/or the terminal hydroxy group on PET. SEM (Scanning electron microscope) photos showed the compatibility of PET/N-HDPE/EGMA- VA is better than PET/N-HDPE. From XRD (X-ray diffraction) analysis, crystallinity of PET decreased when HDPE content increased with the addition of EGMA-VA, which was confirmed by DSC analysis. DMA result showed storage modulus of blends decreased when N-HDPE content increased with incorporating compatibilizer. From tensile test, with increasing N-HDPE content, tensile strength and Young’s modulus decreased, and tensile strength increased with incorporating compatibilizer. For torque of mixer, The values increased when incorporating EGMA-VA, indicating that the possible formation of PET-EGMA-VA copolymer in agreement with previous FTIR and SEM analyses. UV/VIS/NIR (UV/VIS/NIR spectrometers) showed that the values of reflectance of near IR increased in a great degree with inclusion of NIR into HDPE to form PET/N-HDPE composites with or without EGMA-VA compatibilizer. The properties of metallocene catalyzed polyethylene (mPE)/PLA melt biomass blends containing an EGMA-VA compatibilizer, with or without annealing effect of PLA are investigated. FTIR revealed the reaction between the epoxy groups on EGMA and terminal carboxylic acid and/or the terminal hydroxy group on PLA. The results from SEM morphology observation revealed that the dispersed PLA particles sizes tended to decrease with the added compatibilizer due to the enhanced interfacial interaction. DSC and XRD results indicated that characteristic crystal planes at (010) and (103) for PLA tended to disappear, indicating the hindered crystallization with the addition of compatibilizer. Yet, the additional annealing effect tended to increase the crystallization of PLA further. Tensile test results showed the synergistic effect from the added compatibilizer and annealing improved the tensile strength and Young’s modulus. DMA analysis showed a decrease in the dissipation factor for mPE with the addition of compatibilizer with or without annealing effect. For rheological properties, adding EGMA-VA increased viscosity significantly. Overall, the incorporated biobased PLA materials could be helpful in reducing the petroleum-based materials to be beneficial the environment in terms of sustainable development concern.