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    Dyes and Pigments

    Resistance variation of conductive ink applied by the screen printing technique on different substrates

    Abstract

    This research study focuses on the application of conductive ink by the screen printing technique to evaluate the potential of creating printed electrodes and to investigate the effect of washing upon electrical resistance and flexibility. Two conductive inks were applied by a conventional screen printing method on four different textile substrates, 100% cotton, 50%/50% cotton/polyester, 100% polyester and 100% polyamide. The inks were also applied on a multifibre fabric. Atmospheric plasma treatment was applied to improve the adhesion to the samples, and the resistance values were compared with those of non‐treated samples. The values were measured before and after cleaning and washing tests, which were performed to simulate domestic treatment for garments to predict the behaviour of the inks after normal usage of the fabrics. Comfort properties like stiffness of the fabrics were also evaluated after five and 10 washing cycles. It was observed that PE 825 ink forms a thicker film on the fabric surface, contributing to the loss of flexibility of the textile. However, PE 825 ink also produced the best results in terms of durability and lower values of resistance. Polyamide fabrics lost their conductive property after five washing cycles due to weak bonding between the ink and the fibres, whereas cotton fibres provided the best results.

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    Source:: Coloration Technology

          

    Prevention of biofouling on aquaculture nets with eco‐friendly antifouling paint formulation

    Abstract

    Aquaculture, which is an important part of food supply, is usually carried out in cage nets made of textile materials. Fouling organisms settle on the cage nets over time, close the mesh openings, and cause unwanted weight gain. In order to prevent fouling, aquaculture nets are generally treated with antifouling paints. In this paper, warp knitted cage nets made from various raw materials were treated with three different antifouling paints. Econea was used as a biocide to prepare an eco‐friendly antifouling paint formulation, and two copper‐based commercial antifouling paints were supplied for comparison. Antifouling paint‐treated and untreated net samples were immersed in a marine ecosystem next to an aquaculture zone for 6 months. Settlement of fouling organisms on nets was observed by taking underwater photographs at periodic intervals. Following the field study, changes in the structure of the nets and antifouling performance of the paints were evaluated considering the results of underwater photographs, biomass growth, variation in mass and strength tests. Colour fastness of the antifouling paints to sea water was also measured to learn about biocide release and surface hydrophobicity. The results show that copper‐free eco‐friendly antifouling paint is just as effective against the fouling mechanism for all types of nets as copper‐based commercial antifouling paints. The novel eco‐friendly formulation has promising results, which provides an alternative for producers when considering the selection of raw materials.

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    Source:: Coloration Technology

          

    Enhancing the wash fastness of disperse dyes on wool with oxidants

    Abstract

    Disperse dyes are not currently applied to wool commercially, in large part because of inadequate wash fastness, but they do have potential, especially for wool‐polyester blends. In this study, for the first time hydrogen peroxide was investigated to increase the wash fastness of disperse dyes on wool. In the absence of oxidants, 10 disperse dyes from seven classes imparted colours with a range of depths (K/S 2‐26) with wash fastness (grey scale ratings for colour change) grades of 3 to 4‐5. Hydrogen peroxide had only small effects on colours and gave only small enhancements to wash fastness, which were limited to anthraquinone, nitrodiphenylamine, disazo and coumarin dyes. The bleach activators Prestogen W and citric acid enhanced the bleaching effect of hydrogen peroxide but did not assist with raising wash fastness. Hydrogen peroxide in post‐dyeing scouring made the dyeings brighter but did not significantly enhance wash fastness. Ammonium persulphate, which was included for benchmarking with earlier studies, yellowed the wool and decomposed some dyes. This study extends the range of dye classes whose wash fastness on wool can be improved by ammonium persulphate to now include diazo, coumarin and methine, and confirms that oxidants/free radical initiators have potential for enabling the disperse dyeing of wool.

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    Source:: Coloration Technology

          

    Consistency issues in hair spectral reflectance and colour measurements

    Abstract

    The colour shade quality control scenario is ubiquitous within the cosmetic hair colouring industry. Visual inspection is nowadays the go‐to standard for the evaluation of dye application outcomes, even although the increased availability of easily operated spectrophotometers has favoured the introduction of colorimeters in the manufacturing process. Human hairs, however, are very efficient scatterers, and this makes their instrumental measurements more difficult and less consistent. To assess the degree to which this intrinsic property compromises the reliability of spectrophotometric measurements, we tested a variety of samples of human hair locks (swatches), both dyed and undyed, and those of nylon fibre hair swatches. First, we analysed results from two measuring modalities made available by instrumentation: Specular Component Included and Specular Component Excluded. Then, to modify macroscopic spatial orientation, we arranged swatches so that hair strands would cross at varying angles. Measurements confirmed the expected dependencies, namely, the clear influence of the scattered component and of sample orientation on instrumental reading outputs. Having settled on a preferred measuring setup, we analysed measurement variance. Here, we briefly discuss the qualitative visual inspection of spectra, before switching to ΔE to show the unreliability, at least as far as lighter coloured dyes are concerned, of the classic target‐sample measurements which are employed to issue pass‐or‐fail verdicts. Despite quantitative measurements being an asset for quality control, we suggest that greater care should be placed in spectrophotometric readings when human hair is involved, as opposed to more traditional fields of application.

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    Source:: Coloration Technology

          

    Investigation into the effect of a plant‐derived stabiliser on the light and wash fastness of sulphur‐dyed cotton and nylon fabrics

    Abstract

    In this study, cotton fabric and nylon fabric were dyed with a range of commercial sulphur dyes and the light and wash fastness of the coloured fabrics was investigated. The effect of after‐treating the coloured cotton and nylon fabrics with a tannin‐based commercial product, Bayprotect Cl, in the presence or absence of sodium sulphate in the treatment bath, was found to significantly improve the light fastness of the sulphur‐dyed cotton, and the photoprotective effect was partially stable to ISO 105‐C06 washing. In addition, the tannin‐based after‐treatment also improved the colour stability of the dyed fabrics to the perborate‐based ISO 105‐C06 washing. The possible mechanisms for the improved fastness properties are also discussed. The application of sulphur dyes to nylon is potentially commercially useful but has been limited because of the reported poor light fastness of the dyeings. The photoprotective effect of the tannin‐based after‐treatment was investigated with a view to providing the necessary commercial performance. However, it was established that on this fibre, the light fastness improvement was marginal, and the associated wash fastness to oxidative bleach‐based ISO 105‐C06 washing was limited.

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    Source:: Coloration Technology

          

    Investigation into the effect of a plant‐derived stabiliser on the light and wash fastness of sulphur‐dyed cotton and nylon fabrics

    Abstract

    In this study, cotton fabric and nylon fabric were dyed with a range of commercial sulphur dyes and the light and wash fastness of the coloured fabrics was investigated. The effect of after‐treating the coloured cotton and nylon fabrics with a tannin‐based commercial product, Bayprotect Cl, in the presence or absence of sodium sulphate in the treatment bath, was found to significantly improve the light fastness of the sulphur‐dyed cotton, and the photoprotective effect was partially stable to ISO 105‐C06 washing. In addition, the tannin‐based after‐treatment also improved the colour stability of the dyed fabrics to the perborate‐based ISO 105‐C06 washing. The possible mechanisms for the improved fastness properties are also discussed. The application of sulphur dyes to nylon is potentially commercially useful but has been limited because of the reported poor light fastness of the dyeings. The photoprotective effect of the tannin‐based after‐treatment was investigated with a view to providing the necessary commercial performance. However, it was established that on this fibre, the light fastness improvement was marginal, and the associated wash fastness to oxidative bleach‐based ISO 105‐C06 washing was limited.

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    Source:: Coloration Technology

          

    The influence of chemical reaction conditions upon poly(styrene‐methyl methacrylate‐acrylic acid) synthesis: Variations in nanoparticle size, colour and deposition methods

    Abstract

    Monodisperse latex nanospheres of poly(styrene‐methyl methacrylate‐acrylic acid) with different sizes were synthetised by soap‐free emulsion copolymerisation and applied onto polyamide 6,6 fabrics by two methods, ie, gravitational sedimentation and dip‐drawing. Different‐sized nanospheres were synthetised by varying temperature and stirring velocity as reaction parameters. Scanning electron microscopy and scanning transmission electron microscopy were used to evaluate nanosphere sizes and deposition structures. The results showed two different nanosphere structural arrangements on the fabric surface, a hexagonal packed centre structure in the even surfaces and a square arrangement in the out‐of‐plane surfaces. Different colours were observed according to particle size, namely, violet (ca. 170 nm), blue (ca. 190 nm), green (ca. 210 nm), yellow (ca. 230 nm) and red (ca. 250 nm). An iridescence effect was also observed, displaying different colours at different observation angles. By controlling the size of the nanospheres it was possible to obtain different, brilliant and iridescent colours. Using different nanosphere sizes it was possible to obtain different interplanar distances and to control the light scattering in the crystalline lattice planes, obtaining Bragg diffraction patterns.

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    Source:: Coloration Technology

          

    The influence of chemical reaction conditions upon poly(styrene‐methyl methacrylate‐acrylic acid) synthesis: Variations in nanoparticle size, colour and deposition methods

    Abstract

    Monodisperse latex nanospheres of poly(styrene‐methyl methacrylate‐acrylic acid) with different sizes were synthetised by soap‐free emulsion copolymerisation and applied onto polyamide 6,6 fabrics by two methods, ie, gravitational sedimentation and dip‐drawing. Different‐sized nanospheres were synthetised by varying temperature and stirring velocity as reaction parameters. Scanning electron microscopy and scanning transmission electron microscopy were used to evaluate nanosphere sizes and deposition structures. The results showed two different nanosphere structural arrangements on the fabric surface, a hexagonal packed centre structure in the even surfaces and a square arrangement in the out‐of‐plane surfaces. Different colours were observed according to particle size, namely, violet (ca. 170 nm), blue (ca. 190 nm), green (ca. 210 nm), yellow (ca. 230 nm) and red (ca. 250 nm). An iridescence effect was also observed, displaying different colours at different observation angles. By controlling the size of the nanospheres it was possible to obtain different, brilliant and iridescent colours. Using different nanosphere sizes it was possible to obtain different interplanar distances and to control the light scattering in the crystalline lattice planes, obtaining Bragg diffraction patterns.

    …read more

    Source:: Coloration Technology

          

    Green synthesis of reactive dye for ink‐jet printing

    Abstract

    Chloropyrimidine‐based reactive dyes are reported as well suited to textile printing; however, nucleophilic aromatic substitution of chloropyrimidines with amino‐containing chromophores is slow and often suffers from poor yields. In this study, a novel and simple method was developed for the synthesis of chloropyrimidine‐based reactive dye under microwave irradiation. In addition, the dye was also synthesised by conventional heating for comparison, which took both the reaction time and yield into account. The progress of the synthesis reactions concerned were monitored using capillary electrophoresis and the purity of the dye obtained was assessed by thin‐layer chromatography. The structure of the synthesised trichloropyrimidine dye was confirmed by Fourier Transform–infrared spectroscopy and elemental analysis. It was found that the reaction rate of the nucleophilic aromatic substitution carried out under microwave irradiation was 4‐fold faster than that carried out under conventional heating, although the enhancement in product yield was modest. These results suggest that microwave irradiation is an effective technique for the synthesis of chloropyrimidine‐based reactive dyes. The synthesised chloropyrimidine dye was formulated into an ink and applied onto a wool fabric by ink‐jet printing. The printed fabrics were steamed at 102°C for 5‐25 minutes at 5‐minute intervals. Good K/S and rate of dye fixation were obtained, both of which improved with increasing steaming time. The prints obtained exhibited reasonably good light and wash fastness properties.

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    Source:: Coloration Technology

          

    Green synthesis of reactive dye for ink‐jet printing

    Abstract

    Chloropyrimidine‐based reactive dyes are reported as well suited to textile printing; however, nucleophilic aromatic substitution of chloropyrimidines with amino‐containing chromophores is slow and often suffers from poor yields. In this study, a novel and simple method was developed for the synthesis of chloropyrimidine‐based reactive dye under microwave irradiation. In addition, the dye was also synthesised by conventional heating for comparison, which took both the reaction time and yield into account. The progress of the synthesis reactions concerned were monitored using capillary electrophoresis and the purity of the dye obtained was assessed by thin‐layer chromatography. The structure of the synthesised trichloropyrimidine dye was confirmed by Fourier Transform–infrared spectroscopy and elemental analysis. It was found that the reaction rate of the nucleophilic aromatic substitution carried out under microwave irradiation was 4‐fold faster than that carried out under conventional heating, although the enhancement in product yield was modest. These results suggest that microwave irradiation is an effective technique for the synthesis of chloropyrimidine‐based reactive dyes. The synthesised chloropyrimidine dye was formulated into an ink and applied onto a wool fabric by ink‐jet printing. The printed fabrics were steamed at 102°C for 5‐25 minutes at 5‐minute intervals. Good K/S and rate of dye fixation were obtained, both of which improved with increasing steaming time. The prints obtained exhibited reasonably good light and wash fastness properties.

    …read more

    Source:: Coloration Technology

          

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