Dynamic colorimetric properties of mixed thermochromic printing inks

Leuco dye‐based thermochromic inks reversibly change from the coloured to the discoloured state in a defined, comparatively wide temperature region. Inside this region, the colour of a sample depends on the temperature and thermal history, which is known as the hysteresis effect. The colour of such a sample as a function of temperature has the shape of a hysteresis loop. Commercially available thermochromic inks have different loops, narrow or broad, and their shapes range from approximately symmetric to highly asymmetric. These properties are also important in mixtures of inks. The hysteresis loop of a mixture reveals its binary nature if the individual pure inks have well‐separated hysteresis. When inks with close‐separated loops, i.e. with similar activation temperatures, are mixed together, the loop of the mixture fuses together into an apparently single loop. Our research shows that some of their dynamic colour properties could be predicted in advance. However, optic and colorimetric properties of mixtures are not additive.     

Chromic textiles: Colour fastness properties and irreversible colour change behaviour of textiles screen printed with thermochromic,photochromic and hydrochromic colourants

The objective of this work was to study how ultraviolet (UV) light exposure, washing and rubbing can influence colour and dynamic qualities of chromic textiles, and to explore how the results attained can be applied by designers for the development of colour changing palettes. The experimental work was conducted with 74% polyamide and 26% elastane elastics screen printed with thermochromic, photochromic and hydrochromic pigments in diverse colours. Initially, colourfastness properties of each pigment type versus colour were assessed. Although washing and rubbing can interfere in samples' colours by becoming lighter at different degrees, the results attained highlight the poor stability to lighting of thermochromic and photochromic pigments, which also present changes between hues along exposure time. For conventional textile applications, poor colour fastness commonly represents a limitation. This work proposes that the way textile colours and behaviour are permanently affected by the studied conditions can be interpreted as a creative variable in the design process. Research samples with a combination of pigments were developed and tested with a combination of cycles of different fastness tests, namely one washing cycle for every 4 h of UV light exposure, totalling 48 h and 12 washing cycles. Results demonstrate the possibility of creating interactive surfaces capable of displaying a wide range of colours that evolve to static within different hues, over stimuli conditions.     

热致变色显温材料的研制

本文着重阐述了示温涂料的主要成分及其示范原理,并且着重介绍了无机热色性材料的研究情况及其变色机理。     

Influence of stabilizer additives on thermochromic coating for temperature monitoring

Compounds based on smart materials are functional structures that can be used as thermochromic sensors for temperature monitoring in equipment such as pipelines, motors, and heat exchangers. We developed thermochromic coatings based on 1,3,3-trimethylindolino-β-naphthopyrylospiran acrylic polyurethane with and without 2-(2H-benzotriazol-2-yl)-4,6-ditertpentylphenol photostabilizer additives and antioxidant butylated hydroxytoluene and applied them on stainless-steel plates by the spray lay-up method. The samples were analyzed using a weathering chamber with UVA and UVB radiation to monitor their degradation process, revealing complete degradation of the coating without antioxidant and photostabilizer, leading to loss of its thermochromic characteristic.     

Spectral dependence of colorimetric characterisation of scanners

The spectral dependence of the colorimetric characterisation of a typical scanner was investigated. Different colour sets, including ColorChecker SG, Kodak Q‐60 colour input target, a set of plain woven coloured fabrics with a large colour gamut, and randomly selected samples of the Munsell Book of Color were used as training and testing sets in the colorimetric characterisation of a scanner by employing a non‐linear regression method. The coefficient matrices were optimised for each particular media in the training stage and used to predict the device‐independent colorimetric data, i.e. CIELab values of other media from their corresponding RGB values measured by the scanner. In order to extract the differences between the applied sets and determine the actual dimensions of their reflectance spectra, the principal component analysis technique was employed. As expected, it was observed that the different sets benefit from diverse dimensional properties and, in some cases, the spectral behaviours of the first few eigenvectors were apparently different. It was demonstrated that scanner colorimetric characterisation depended on the spectral properties of the applied colour set in the training stage and, consequently, the testing errors increased with increasing the spectral dissimilarity between the sets that were used in training and testing sequences. It was concluded that, to achieve better colour reproduction results, the scanner should be characterised for each media with specific spectral properties.     

几种常用橡胶着色剂对三元乙丙橡胶老化性能的影响

在相同配合的三元乙丙橡胶配方中,分别使用橡胶大红、立索尔宝红、永固黄、酞菁绿、酞菁蓝后,混炼胶料硫化特性和物理机械性能相近。但老化后,物理机械性能表现出较大差异。160℃×72 h老化后,对拉伸强度的影响,酞菁绿和酞菁蓝是橡胶大红和立索尔宝红的2.5～3倍,永固黄的影响居其间;对扯断伸长率的影响,酞菁绿、酞菁蓝和永固黄是橡胶大红和立索尔宝红的1.3～1.5倍;对硬度的影响,酞菁绿和酞菁蓝是橡胶大红、立索尔宝红和永固黄的1.3～1.4倍;对撕裂强度的影响,永固黄是酞菁绿、酞菁蓝、橡胶大红和立索尔宝红的3～4倍。且在不同的老化条件下,其影响表现出相同的差异趋势。     

The thermochromic properties of the ceramic colour standards

Thermochromism is a reversible change oftransmittance, reflectance, or absorptance induced by a change of temperature. Photochromism is the corresponding effect induced by optical radiation. These effects can occur in the use of reflectance standards, as they may undergo a considerable temperature rise when subjected to the polychromatic irradiation used by many measuring instruments. An investigation of any thermochromic (and photochromic) properties of the twelve Ceramic Colour Standards is described. It is shown that thermochromic effects are only significant to a very small extent in about half of the standards and not at all in the remainder, while there is no evidence of any photochromism.     

Andean colors: A colorimetric registration in pre‐Columbian textiles from Northern Chile

This article shows the colorimetric data obtained from pre‐Columbian northern Chilean textiles and their subsequent analysis for the construction of a color chart. As part of a more extensive study investigating the fundamental pillars of the textile language associated with pre‐Columbian weaves, a registration of colorimetric data was carried out on 42 textile pieces with a total of 203 colors mostly provided by the Chilean Museum of Pre‐Columbian Art. The results are presented in terms of CIELAB coordinates. The colors obtained showed a considerable percentage of reds and browns. The recorded values can contribute to the preservation of cultural heritage and the esthetics of current Chilean identity as they can be used in new industries, contexts, and applications. Subsequently, the colorimetric data obtained could be transferred to other color systems, so that users from different sectors might have access to this cultural legacy, understanding the limitations of color production in mixed media.     

可逆热致变色材料的微胶囊包封及性能研究

用环氧树脂E-12作壁材,低分子聚酰胺200为固化剂,采用原位聚合法,对可逆热致变色有机复配物进行微胶囊包封,用SEM和TGA测定了微胶囊的形态结构和热行为。研究包封条件对微胶囊结构和性能的影响,结果表明,最合适的反应条件是:壁材与变色芯材质量比为0.2~0.6,乳化温度50℃,固化反应分5段升温。此条件下可以制得结构致密完整、具有良好透明性、耐热性和耐溶剂性的变色微胶囊,能满足纺织品涂料印花的要求,微胶囊粒径在5μm以下。     

Investigation into the development of novel lanthanide-based luminescent colorants for application to textiles and paper materials

This article describes the synthesis and application of lanthanide-based luminophores for visualisation under short wavelength ultraviolet (UV) activation (typically 254 nm). Luminophores are chemical compounds which re-emit light of longer wavelength than typical fluorescence and phosphorescence, following photoexcitation, because of efficient energy transfer from the ligands to the lanthanide ion emission levels. The luminophores described in this article are all derived from europium and terbium metal complexes and cover the complete colour gamut. Selection of appropriate ligands allows for water solubility or water insolubility (if required pigment or disperse “dye” applications). Similar to dyeing or printing processes, the anionic complexes can be applied to polyamide fibres or to cellulosic fibres, whereas dispersions of the non-ionic complexes are suitable for polyester or cellulose acetate fibre application. The water-soluble derivatives are also suitable for ink-jet printing and the water-insoluble derivatives are suitable for lithographic or intaglio paper printing. The novel complexes are excited by radiation below 300 nm and thus cannot be activated by sunlight (the earth's atmosphere prevents light below about 300 nm reaching the surface). Accordingly, the photo-stability of the dyed materials and prints obtained is excellent. These materials could be used in security marking applications, for example bank-notes and passports, where they could replace the current fluorophores that are rendered visible under near UV light (typically 365 nm) illumination but exhibit relatively poor photo-stability. The development of an RGB (red, green and blue) colour palette for inkjet printing based on these innovative luminophores will significantly support the design of digitally printed security features.     

The temperature and strain-rate dependence of mechanical properties in polyoxymethylene

The computer aided design approach used in current applications of semicrystalline polyoxymethylene (POM) requires high strain-rate mechanical data. The primary aim of this work has been to measure the room temperature modulus and tensile strength of injection molded samples of POM of different molecular weights at cross-head speeds of between 10^?5 ms^?1. We observe no major transition in bulk mechanical behavior in this range of test speeds, the Young's modulus E, in particular, showing little strain rate dependence. This is rationalized on the basis of tensile tests over a range of temperatures, these indicating room temperature to correspond to the plateau in the E(T) curves (T_g for these materials is taken to be ?70°C, and the DSC melting onset occurs at ～ 170°C). The tensile strength increases as ～log(d?/dt) and the behavior is found to be highly nonlinear, strains to fail of the order of 1 being observed even at the highest strain rates, depending on the molecular weight. It is believed that the yield stress of th crystalline regions determines the tensile strength above T_g, the higher degree of crystallinity associated with lower molecular weights resulting in a slightly higher tensile strength. Nevertheless, failure is qualitatively brittle, with no necking and relatively little permanent deformation. This behavior is discussed in terms of morphological investigations of the fractured samples by optical and scanning electron microscopy (SEM). In attempting to relate ultimate failure to the molecular/crystalline structure of the samples, measurements of the critical stress intensity for crack initiation in mode I opening, K_IC, as a function of crystallization temperature T_c have been carried out using compact tension specimens machined from injection molded and compression molded plaques. K_IC increases with molecular weight and decreases with T_c at low test speeds (in spite of an increase in crystallinity with T_c). This is accounted for in terms of a crack shielding model for crack initiation and of molecular rearrangements occurring during crystallization which lead to a decrease in the effective entanglement density with T_c. The implications of this model are then compared with K_IC results over a range of cross-head speeds and temperatures.     

Dynamic mechanical properties of polymer melts: The effect of molecular weight distribution on the temperature dependence of viscoelastic properties

An experimental investigation of the dynamic mechanical response of molten polymers was performed using the Maxwell Orthogonal Reheometer. One purpose of the study was to evaluate the effect of molecular weight distribution on the temperature dependence of viscoelastic properties. Data were obtained over a range of temperatures for both monodisperse and polydisperse materials which indicate that viscoelasticity is highly temperature dependent only for monodisperse polymers. On a molecular basis the reduction in temperature sensitivity for polydisperse materials logically can be attributed to the influence of the low molecular weight species present in a distribution on the relaxation spectrum. Since the relaxation spectrum largely determines all viscoelastic functions, the observations made from th dynamic data shown in this paper can be generalized to all viscoelastic experiments.     

Preparation of reversible thermochromic building coatings and their properties

Thermochromic dyes reversible at normal ambient temperatures have been identified and microencapsulated using an emulsion polymerization process. By blending microencapsulated thermochromic dyes and nonthermochromic pigments with ordinary building coatings, thermochromic building coatings, in which colors change reversibly from warm tones to cool tones at about 18 °C have been obtained. The application and performance properties of the coatings were measured, and it was found that adding thermochromic dyes did not degrade the properties of coatings. The aging results showed that the aging properties of the coatings were not ideal; the reasons will be given in another paper. 1923 Siping Road, Shanghai, P. R. China. Project Supported by National Natural Science Foundation of China (59978036).     

The effect of colorants on the properties of rotomolded polyethylene parts

An experimental study is reported on the effect of colorants on the warpage, shrinkage, and mechanical properties of rotomolded polyethylene (PE) parts. Five pigments were investigated (titanium dioxide white, cadmium oxide yellow, iron oxide red, carbon black, and phthalocyanine blue). Their concentration was in the range of 0.11 to 0.36 wt%. The pigments were added to the linear low-density polyethylene (LLDPE) by various techniques, dry blended in low intensity or high intensity mixer or compounded with a single-screw extruder. Some blends also contained 0.077 wt% zinc stearate as surfactant. It was found that zinc stearate surfactant in the dry blend increases warpage by about a factor of 2 and shrinkage by ˜ 30%, but color quality and powder handling properties are improved. The dry-blended pigments concentrate along the fusion lines of the PE particles in rotomolded parts, which results in >50% decrease of impact strength with some pigment-surfactant combinations. Mold pressurization minimizes warpage and shrinkage, but causes no significant improvement in impact resistance. Impact resistance can be improved by using compounded pigments or making two-layer parts with a pigmented outer and unpigmented inner layer.     

The dependence of magnetic properties on temperature for rare earth ErCrO3 chromites

Multiferroic ErCrO₃ was synthesized and the detailed magnetic as well as ferroelectric properties were investigated. The dc magnetization shows that ErCrO₃ undergoes a antiferromagnetic ordering at T_N = 133 K due to the Cr³⁺–Cr³⁺ followed by weak ferromagnetic ordering. Around T_SR ≈ 22 K, ErCrO₃ exhibits a spin reorientation from Γ₄ to Γ₁. And the stability of the ferromagnetic Γ₄ phase increases with the applied magnetic field increasing. Furthermore, at lower temperature, it shows weak antiferromagnetic ordering of Er³⁺. We also present the low temperature polarization data for ErCrO₃ and find a remarkable decreasing of polarization around T_N = 133 K on increasing temperature, this effect might be due to the coupling between magnetic and ferroelectric order parameters, and the magnetic field suppresses the polarization which demonstrates convincingly the strong magnetoelectric (ME) coupling in ErCrO₃.     

Research on the preparation of reversibly thermochromic cement based materials at normal temperature

In this paper, reversibly thermochromic cement at normal temperature was prepared by adding reversibly thermochromic microcapsules in white Portland cement. The research results showed that the color of the reversibly thermochromic cement added with a kind of blue reversibly thermochromic microcapsule with 30 °C switching temperature (B30, in which B is for the blue color, 30 is for the switching temperature, and the similar way is used in the following of the paper) could be changed reversibly from blue at lower temperature to white at higher temperature, and the switching temperature was about 42 °C. When added with a kind of red reversibly thermochromic microcapsule with 30 °C switching temperature (R30) or a kind of green reversibly thermochromic microcapsule with 30 °C switching temperature (G30), the color could be reversibly changed from red or green to white, and the switching temperature was about 58 °C. The kind of red reversibly thermochromic microcapsule could thus meet the needs of warm tone in winter and cool tone in summer in buildings. When the thermochromic microcapsule B30 was added in white Portland cement, the water content of the standard consistence of cement slurry increased by about 13%, and the mechanical properties, such as flexural strength and compressive strength, decreased by 20%-40%, but the setting time and the soundness of cement were not affected. All the research results indicate that the prepared material could meet the demand for creation of thermally comfortable environment of buildings. Through changing the solvent, the thermochromic microcapsule R5, G5 and B5 etc. were prepared further. Then by mixed 10% R5, G5 and B5 with white Portland cement, the switching temperatures could be lowered down to 26 °C, 26 °C and 17 °C respectively. The thermal effect of improved reversibly thermochromic cement based material (white cement mixed with 10% black microcapsule, and its switching temperature was about 24 °C) showed that it could warm buildings in winter and avoid buildings over-heated in summer.     

Time and temperature dependence of the mechanical properties of polystyrene bead foam

Tensile and compressive properties of polystyrene bead (PSB) foams at room temperature for strain rates from 10^?3 to 10⁵ min^?1 can be represented as nearly linearly increasing functions of modulus or stress versus the logarithm of the strain rate. The shear modulus and tensile data, including failure properties, on 0.054 g/cc PSB foam at various temperatures and strain rates can be represented by master curves of log (stress or modulus) versus log (reduced strain rate). These master curves are formed by a time and temperature superposition method, wherein data at one temperature are superposed on data at another temperature by a shift along the log (strain rate) axis. These time–temperature shift factors are calculated using a form of the Arrhenius equation.     

Light fastness and high‐temperature stability of thermochromic printing inks

Thermochromic printing inks are known for their low stability under the influence of various external conditions, but the consequences of the phenomenon on dynamic colorimetric properties have not yet been analysed. In this work, thermochromic prints were exposed to light and heated at two different temperatures, 150 and 200 °C, for varying time periods. The changes to the dynamic colour properties of the samples were described. It was found that both exposure to light and heating to high temperatures degrade the dynamic properties of thermochromic inks; however, they have different effects on the colour hysteresis. The corresponding loops contract with light exposure and heating, which is best described by the area of the entire colour loop. Exposure to light broadens the corresponding loop, while heating makes it narrower. The chemical stability of inks after exposure was also analysed by forced oxidation applying weakly ionised oxygen plasma. Stability of thermochromic samples is a combined effect of the binder, the polymeric shell and the active core inside the pigment capsules. The results show that poor stability against light and high temperatures has different origins.     

An evaluation of thermochromic prints based on microencapsulated liquid crystals using variable temperature colour measurement

A variable temperature colour measurement technique has been developed to characterise the temperature-dependent colour change, known as 'colour play', observed with thermochromic prints based on microencapsulated liquid crystals. The effect is most pronounced over a black background. The liquid crystals exhibiting the thermochromic effect adopt a chiral nematic phase with an underlying smectic A phase. A variety of methods for presenting and interpreting the data obtained, as the colour of the print passes through the spectrum, is explored. The effect of temperature on the wavelength of reflected light, a * b 相似文献