Amalid Mahmud-Ali

Anthocyanin dyes extracted from grape pomace for the purpose of textile dyeing

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

Efficient processing of raw material defines the ecological position of natural dyes in textile production

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.

Aqueous thiocyanate–urea solution as a powerful non-alkaline swelling agent for cellulose fibres

For many applications cellulose fibres are treated with concentrated solutions of swelling agents to increase reactivity and to achieve reorganisation of fibre structure. Representative examples are caustic soda, potassium hydroxide solution or liquid ammonia. These highly concentrated media bear considerable safety hazards during the technical handling thus alternative swelling agents are of interest. The thiocyanate-urea system investigated in this work offers high swelling potential for regenerated cellulose fibres. Experiments with different cations of M(+) in M(+) SCN(-) demonstrate the significant influence of the cation on the degree of fibre swelling. In concentrated NaSCN/urea solutions, at 80 °C, lyocell fibres expand the diameter from 12-14 to 100 μm. The treatment in the swelling agent also led to a significant increase in the water retention value which was accompanied by a strength loss of 20-40% of the initial value. FTIR analysis of treated fibres did not indicate substantial changes in structure of the cellulose polymer. Limited weight loss of up to 20% was observed despite the high expansion of the fibre.

Natural dyes from food processing wastes

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.