The present investigation describes the development of a regression model for dry colour prediction based on the colour of wet leather. Such a prediction will be useful in the colour matching of leather – the time delay in drying of wet leather and determination of the final colour can be avoided. The use of computer technology interfaced with a reflectance spectrophotometer provides a novel approach to the prediction of dry colour from wet colour. In this study, five different regression models, i.e. linear fit, log fit, quadratic fit, log quadratic fit and cubic fit, were developed, with the dry reflectance of the leather sample as a dependent variable and the wet reflectance of the leather as an independent variable. The relationship between moisture content and surface leather colour, a prerequisite for enabling prediction, was studied. The obtained log quadratic model can be used for accurate prediction of dry colour from wet colour.

In this study, a novel metal-free phthalocyanine and three metallophthalocyanines carrying four 2-[2-(4-tert-butylphenoxy)ethoxy groups on the periphery were prepared by cyclotetramerisation of a dinitrile derivative in the presence of the corresponding divalent metal salts [zinc(ii), cobalt(ii), copper(ii)]. These new phthalocyanine compounds have been characterised by infrared, ¹H and ¹³C nuclear magnetic resonance and electrospray mass spectroscopies and elemental analysis. The electrochemical properties of the metal-free, zinc(ii) and cobalt(ii) phthalocyanines were investigated by cyclic voltammetry and differential pulse voltammetry methods. The cobalt complex showed a metal-based reduction process, while the metal-free and zinc(ii) phthalocyanines showed ligand-based electron transfer processes. It has been found that the absorption spectra substantially depend on concentration. It has been shown that these changes are attributable to the association of the phthalocyanine molecule. The number of molecules in the associates and the equilibrium constants for this association are determined.

True colour measurements of wastewater samples, in terms of American Dye Manufacturers' Institute values, were used to evaluate the effectiveness of decolourisation of textile wastewater using spent green tea leaf powder waste. Raw wastewater samples with a true colour of 868 ADMI were used in the batch adsorption experiments. Results revealed that the true colour removal efficiency of the raw textile wastewater was high in acidic solution and at high temperature, indicating an endothermic nature of the system. The major functional groups of the green tea leaf powder waste involved in adsorption were identified by Fourier Transform-infrared spectroscopy analysis. Adsorption kinetic data were modelled using the modified Freundlich and intraparticle diffusion kinetics equations. Fitting results of the Langmuir adsorption isotherm showed that the adsorption capacity of the green tea leaf powder waste was 775 ADMI g⁻¹, which is higher than that of powder activated carbon (526 ADMI g⁻¹). The low activation energy values (13.9 kJ mol⁻¹) suggested that adsorption was governed by a diffusion process and the reaction involved a physisorption mechanism. From the perspectives of waste utilisation, remarkable colour adsorption capacity and inexpensive and abundant availability, green tea leaf waste is an attractive alternative for decolourisaton of textile wastewater. Because high temperature favours colour removal, green tea leaf powder can be directly applied in raw textile wastewater treatment.

Photoredox pairs consisting of 1,4-naphthoquinone dyes and commercially available hydrogen donors (2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole and 2,5-dimercapto-1,3,4-thiadiazole) are found to be effective initiator systems for the radical polymerisation of trimethylolpropane triacrylate under visible light. The efficiency of these initiator systems is discussed in terms of the free energy change for the electron transfer process from the dye to the hydrogen donor. The results show that the photoinitiation ability of tested photoredox pairs depends on the structure of both the dye and the hydrogen donor.

The compatibility of three disperse dyes, CI Disperse Orange 30, CI Disperse Red 167 and CI Disperse Blue 79, which are commonly used as a trichromatic combination for conventional dyeing, was studied in supercritical carbon dioxide dyeing. Both the dyeing rate and the build-up of the selected dyes were measured. Experimental results showed that they were quite compatible. The dyeings of a binary combination (CI Disperse Orange 30 and CI Disperse Blue 79, mass ratio 1:1) and a ternary combination (CI Disperse Orange 30, CI Disperse Red 167 and CI Disperse Blue 79, mass ratio 1:1:1) at different dye concentrations showed an on-tone uptake and presented the same metric hue angles. This proved that the selected dyes could form a useful trichromatic combination in supercritical carbon dioxide dyeing. Furthermore, the uptake and exhaustion of the single dyes in supercritical carbon dioxide dyeing were similar to those in aqueous dyeing, implying that the dyeing media play only a minor role in the dyeing of polyester fibres with disperse dyes.

When β-cyclodextrin was adopted as a dye catcher, the degree of dye migration onto adjacent fabrics as well as onto the coated surface was greatly reduced, while other physical properties, such as waterproofness and breathability, remained unaffected. When acetylation of β-cyclodextrin was carried out, its solubility in an organic solvent, including methyl ethyl ketone and toluene, was greatly improved. Hence, it provided a smoother coated surface and an excellent antimigration effect in a direct-coating system. These results confirm that β-cyclodextrin is an effective dye catcher in a polyurethane-based coating system, in which it prevents the migration of the dyes from coated polyester fabrics onto adjacent surfaces. The solubility of cyclodextrin can be optimised by a chemical modification of its cyclodextrin-hydroxyl groups. Hence, this host–guest interaction demonstrates a universal and effective platform for antimigration coating systems.

In recent years, many advanced composite materials based on poly(p-phenylene-2,6-benzobisoxazole) fibres have become prominent in applications requiring high-strength and flame-retardance such as body armour, industrial reinforcement materials and military camouflage. However, the application of these fibres used as protective clothing is limited due to difficulties in dyeing and printing. In the present work, a process for pretreating poly(p-phenylene benzobisoxazole) fibre with polyphosphoric acid was applied, and the pretreated fibre was then dyed with disperse dyes via dip dyeing. Effects of pretreatment temperature and time on structure and properties were investigated. Surface morphology, crystallinity, chemical structure and degree of orientation of fibres were characterised. The results indicated that the supramolecular structure of the fibre was relaxed or swelled by polyphosphoric acid in the pretreatment process, so that the dyeability of poly(p-phenylene benzobisoxazole) fibre was improved, with satisfactory dye exhaustion, K/S values and dyeing fastness. Also, with the appropriate pretreatment process, the swelling effect of polyphosphoric acid on the structure of poly(p-phenylene benzobisoxazole) fibre was limited, so as to control the decrease in tensile strength and limiting oxygen index of the dyed fibre.

The presence of aromatic amines in effluent from dyeing processes of the textile industry is an added problem to the high coloration typical of this type of effluent. The main objective of the present work was to eliminate these two problems simultaneously by electrochemical treatment using bath solutions containing three azo dyes. For the analysis of amines, a liquid–liquid extraction method was developed as an easier and faster alternative to the method described in the standards and widely used in analytical laboratories. Four amines (aniline, o-toluidine, 4-chloroaniline and 4-aminobiphenyl) were detected by GC-MS in the residual azo dye baths. A total amine concentration of between 2.5 and 1 ppm was detected, 4-aminobiphenyl being the main compound. Both residual colour and amines were removed by electrochemical treatment carried out at three current densities (3, 24 and 40 mA/cm²). At 24 mA/cm², more than 90% of colour removal was achieved, and the total amine concentration was reduced to below 0.15 ppm.

Novel, tunable solid-state emitters based on anthracene groups were synthesised and characterised by spectroscopy and elemental analysis. Their solid-state photoluminescence properties were studied. These fluorophores display interesting solid-state emission properties with an emission at wavelengths ranging from 550 to 650 nm when excited by a 325 nm helium–cadmium laser at room temperature. In particular, among them, 1,6-di(9-anthryl)hexa-1,5-diene-3,4-dione, 2-[4-(2-benzoxazolyl)phenyl]-4,5-bis[2-(9-anthryl)vinyl]-1H-imidazole and 2,3-bis[2-(9-anthryl)vinyl]quinoxaline show red, yellow and green emission, respectively, at 650, 584 and 550 nm. The results demonstrated that the luminescent colours can be tuned from red to yellow and green by simply varying molecular structure. Besides, 1,6-di(9-anthryl)hexa-1,5-diene-3,4-dione also exhibited an upconverted red fluorescent emission peak at around 675 nm under femtosecond excitation at 800 nm.

Dyes have been applied and are playing an increasingly important role in many industries, including the textile, printing, medical and energy industries. Their wide applications imply that specific dyes possessing given properties need to be effectively designed. The present review aims to survey information related to activity/property research of dyes that has been published in the past two decades. Emphasis is laid particularly on studies based on quantitative structure–activity/property relationships that have contributed to the theoretical design and application of dyes. Finally, the perspectives of quantitative structure-activity/property relationship studies are set out in order to show how this method may be used to design new dyes and to evaluate their different properties. The challenges facing these studies are also outlined.

Three chitosan-ZnO composites were prepared by the chitin deacetylation process using zinc chloride as source material and sodium hydroxide as precipitant. The physical characteristics of chitosan-ZnO composites were studied using Fourier Transform infrared spectroscopy and scanning electron microscopy. The adsorption of a chromium complex dye onto commercial chitosan, prepared chitosan and chitosan-ZnO composites was investigated in aqueous dye solution. Dye calibration was carried out by UV-vis spectroscopy. The calculated dye adsorption values for commercial chitosan, prepared chitosan, and chitosan-ZnO composite samples are 0.0086, 0.0137, and 0.0214 mg/g respectively, indicating that the chitosan-ZnO composites have better dye adsorption capacity than commercial chitosan and prepared chitosan. The experimental isotherm data for the composites fitted the Langmuir isotherm model well. Thus, the chitosan-ZnO composites can be used as an effective biosorbent for the removal of anionic dyes.

Three novel cationic liposomes were prepared from commercial soybean lecithin (neutral liposome) and stearylamine (cationic liposome) as a catalyst or accelerating agent for the alkaline hydrolysis of polyester fabric. The formation of 1:1, 1:6 and 1:12 cationic liposomes was confirmed by transmission electron microscopy, nitrogen content and Fourier Transform-infrared spectroscopy. Factors affecting the alkaline hydrolysis performance of polyester fabric in the presence and absence of cationic liposomes were investigated. Size measurements of the three cationic liposomes showed that the vesicle size was 27.88 nm for the 1:1 cationic liposome, 15.57 nm for 1:6 and 10 nm for 1:12, in comparison with 50 nm for neutral liposome. The results showed that alkaline hydrolysis in the presence of cationic liposomes improves the hydrophilicity and dyeability of polyester fabric and creates more carboxylic groups on the fabric. The silky polyester fabric was characterised by scanning electron microscopy, tensile strength, elongation at break, crease recovery angle and surface roughness to prove the success of the cationic liposomes as accelerating agents in the alkaline hydrolysis process. The results also indicate that the colour strength of hydrolysed polyester fabric in the presence of cationic liposomes dyed with disperse dye was slightly higher than that obtained in the absence of cationic liposomes and with unhydrolysed fabric. Furthermore, the fastness properties of hydrolysed polyester in the absence and presence of cationic liposomes do not vary.

Characterisation targets usually include a set of physical coloured samples. A characterisation model can be derived between the colorimetric values (tristimulus values) and camera responses (RGB values) taken from an imaging device such as a digital camera capturing the colours in the target. The performance of such a model is highly dependent upon the number of colours and the colour region in the characterisation target. An ideal characterisation target should provide accurate model prediction without requiring too many samples. In this paper, a computational method is presented for colour selections to train a camera characterisation model based on a fourth-order polynomial model including 35 terms. Compared with other available methods, the newly developed method performed better. It is proposed that this method be applied to generate generic targets in terms of colorimetric values. These targets should work reasonably well for a wide range of materials.

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.

In this study, silk fabric samples were dyed according to various procedures with buckthorn (Rhamnus petiolaris Boiss) and walloon oak (Quercus ithaburensis Decaisne) extracts. Reversed-phase high-performance liquid chromatography with diode-array detection was utilised for the identification of dyes present in the dyed silk fabrics and the plant extracts. The extraction of dyes was carried out with a hydrochloric acid/methanol/water (2:1:1; v/v/v) mixture. The colour coordinates of the silk fabrics were measured, and the rubbing, wash and light fastness properties of the dyed silk materials were determined and are discussed.

Commercial thermochromic colorants were applied to a conductive cotton fabric prepared by using nichrome/cotton core-spun yarns in weft and 100% cotton in warp. The fabrics were pretreated and coloured with thermochromic pigments in isolation, in combination with each other, or in a mixture with a non-thermochromic pigment. The weft yarns were joined to allow passage of current through the fabric to enable ohmic heat generation to increase fabric temperature. The heat generation and temperature rise could be controlled by monitoring the voltage applied. The colour of the samples changed gradually with an increase in temperature, and significantly so when the temperature of the fabric rose beyond the activation temperature of the thermochromic colorant. The temperature-dependent properties of commercial thermochromic colorants were determined using a spectrophotometer. Wash fastness of the samples was found to be fair in all cases except with the yellow colorant. Predetermined colour effects, such as camouflage or novel design, can be produced by combining thermochromic colorants with conventional pigments or thermochromic colorants with different activation temperatures.