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The design of flexible sensors which can be incorporated in textile structures is of decisive importance for the future development of wearables. In addition to their technical functionality, the materials chosen to construct the sensor should be nontoxic, affordable, and compatible with future recycling. Conductive fibres were produced by incorporation of carbon black into regenerated cellulose fibres. By incorporation of 23 wt.% and 27 wt.% carbon black, the surface resistance of the fibres reduced from 1.3 &times, 1010 &Omega, &middot, cm for standard viscose fibres to 2.7 &times, 103 and 475 &Omega, cm, respectively. Fibre tenacity reduced to 30&ndash, 50% of a standard viscose, however, it was sufficient to allow processing of the material in standard textile operations. A fibre blend of the conductive viscose fibres with polyester fibres was used to produce a needle-punched nonwoven material with piezo-electric properties, which was used as a pressure sensor in the very low pressure range of 400&ndash, 1000 Pa. The durability of the sensor was demonstrated in repetitive load/relaxation cycles. As a regenerated cellulose fibre, the carbon-black-incorporated cellulose fibre is compatible with standard textile processing operations and, thus, will be of high interest as a functional element in future wearables.

The food and beverage industry releases considerable amounts of wastes which contain natural dyes. Such wastes could serve as a sources for the extraction of natural dyes for textile-dyeing operations. The extraction of brilliant yellow and red colours from fruits and vegetables is of particular interest. Wastes, e.g. pressed berries, pressed grapes, distillation residues from strong liquor production, and wastes and peels from vegetable processing, have been extracted with boiling water and test dyeings on wool yarn were performed. Colour strength, shade and fastness properties of the dyeings have been tested. The extracts were applied as direct dyes and in the presence of iron(II) or alum mordants. The results prove the potential of such wastes as a source for natural dyestuff extraction. To obtain textile dyeings with acceptable fastness properties, however, rigorous selection of dyes and development of suited processes is required. A considerable number of red natural dyes need further research to optimise the low level of fastness to light. Copyright © 2005 Society of Chemical Industry

BACKGROUND: Pomace from different grape varieties was studied with regard to the content of extractable anthocyanins. RESULTS: Total anthocyanin concentrations of 24.5–126 mg dm−3 were found in the extracts. The amount of extractable pigment was dependent on the variety of grape. The extracts were applied in textile dyeing operations using cotton fabric pre-mordanted with tannin as textile substrate. Red/violet shades were obtained that showed good water-fastness; however, limited light-fastness indicated need for improvement to fulfil requirements for textile application. CONCLUSION: Colour measurement by means of CIE-Lab coordinates and Kubelka–Munk value showed a direct correlation between extractable anthocyanin concentration and colour depth of the dyed material. Thus the analytically determined concentration of anthocyanins in the aqueous extract can serve as a measure of quality of grape pomace as raw material for textile dyeing application. Copyright © 2007 Society of Chemical Industry

Publisher Summary This chapter provides an overview of the potential for natural dyes to be used in textile dyeing, with special reference to plant-based materials found in food processing and food chain waste streams. It also discusses the requirements that have to be met for successful application of natural dyes in textile dyeing operations. Natural dyes present in plant wastes have to be extracted for use in the dyebath. The extraction step is discussed with regard to energy and chemicals, which forms a basis to compare different strategies to handle natural dyes in full technical scale. Results of a screening study to identify suitable wastes, released from the food and beverage industries, as potential sources for natural dyes are also illustrated in the chapter.

The production of natural dyes from plant sources available in the moderate climate of Austria (Europe) has been studied. Besides direct agricultural production, additional sources e.g., bark from timber industry and wastes from food industry have been investigated. Model calculations of energy consumption indicate that stabilised plant material e.g., dried plants, is favourable compared to dyestuff extracts. The low dyestuff content of the crops demands extraction of huge amounts of plant material, thus extraction should be performed in water only. Dyeing experiments indicate that based on a selection of dyestuffs and mordants an acceptable quality level can be reached.