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Abstract The development of halochromic textile materials could lead to interesting end-use applications as it offers the potential for flexible pH-sensors with a first warning signal. Research on halochromic textiles, especially on the development of these materials using a simple and economic beneficial dyeing process, is however very limited. Therefore, we studied color-changing textile materials with a pH-sensitivity based on the dyeing of conventional textiles with standard water-soluble pH-indicator dyes. In a first broad screening, a set of pH-indicators is evaluated on their dyeing performance and their color change with a change in pH. After this, some promising indicators (Brilliant Yellow and Alizarin) are selected and studied in more detail. It was found that the indicators show different characteristics on the textile materials compared with the solution due to dye-fiber interactions. The properties of the pH-indicator dyes are also dependant on the fiber type. Moreover, in case of Brilliant Yellow this thesis was confirmed by Raman spectroscopy. Generally, it can be concluded that it is feasible to develop a pH-sensor with pH-indicator dyes and conventional textile materials using a standard dyeing process.
Key words dyeing, color changing textiles, halochromism, Brilliant Yellow, Alizarin
In the last decade smart textiles have become the subject of many studies all over the world. Within the group of smart textiles, a growing interest in color change materials, or socalled chameleon textiles, is recognized. These materials can change their color due to a change of several external triggers, such as temperature (thermochromism), light (photochromism), electricity (electrochromism), polarity of solvent (solvatochromism), pH (halochromism), etc [1]. At first sight such types of materials seem to be unwanted [2]. Yet, they can be useful in a variety of situations. A color change is immediately visible for everyone and can, for this reason, perform a first signal or warning function. Furthermore, when covering large surfaces, they are capable of giving a local signal by a local color change and this without having to incorporate many separate local sensor systems. However, the study of color change materials is still preliminary. Research about the application of chromic dyes on textiles by conventional dyeing processes is limited. The dyes are generally incorporated in the textile structures by coating, extrusion or microencapsulation [3-5].
Even though the majority of...