Fibres and Textiles (2) 2020 58 INVESTIGATION OF THE COLORFASTNESS PROPERTIES OF NATURAL DYES ON COTTON FABRICS Shariful Islam 1 , Shaikh Md. Mominul Alam 2 and Shilpi Akter 3 1 Department of Fabric Engineering, Bangladesh University of Textiles, Tegjaon, Dhaka, 1208 2 Department of Textile Machinery Design and Maintenance, Faculty of Science and Engineering, Bangladesh University of Textiles, Tegjaon, Dhaka, 1208 3 Department of Fabric Engineering, Faculty of Textile Engineering, Bangladesh University of Textiles, Tegjaon, Dhaka, 1208 sharifultextiles@gmail.com; head.tmdm@butex.edu.bd; shilpiakter@butex.edu.bd Abstract: The aim of this research was to identify the color fastness properties of the natural dyes on cotton fabrics using different types of dyes like mehedy/henna, turmeric, tea leaf and pomegranate, which were cheap, easily obtainable and ecofriendly. The findings established that, mehedy/henna dye reacted with cellulose of cotton in alkaline condition to form a permanent covalent bond between the dye and the cellulose, which would not be removed by frequent washing treatment with steaming water in neutral conditions and exposed excellent color fastness properties. Mehedy dye had a reactive group that acted as an integral part of fiber and this covalent bond was formed between the dye molecules and the terminal reactive group. With necessary treatments these dyes were collected from nature in powder form and liquefied them for dyeing on 100% cotton mercerized fabrics with necessary chemicals and auxiliaries as natural dyes had affinity towards cellulosic fibers. Continuous dyeing process was carried out with the facilities of "Pad Dye Pad Steam" machine in open width form and then steamed wash to fix the colors with natural dyestuffs. Dyeing process and color fastness tests were carried out in accordance with the test method provided by AATCC and ISO standards. Dye absorption and color strength tests were conducted with the facilities of lab spectrophotometer "Data Color Spectra Flash SF600" in agreement with Kubelka Monk equation through the spectral reflectance, absorption and scattering characteristics of the samples. "Nicolet IS 50 FTIR" instrument was applied to attain the color intensity properties through the passage of Infrared Radiation (IR) within the spectrum. This research was practice based and the findings were advantageous to the personnel involved in textile industries who were responsible for dyeing the fabrics with natural dyes and to controlling of their color fastness properties. Keywords: Natural dyes; color fastness; FTIR; spectrophotometer; dye absorption; color strength; color intensity; infrared radiation. 1 INTRODUCTION The research under discussion was undertaken in the field of cotton fabric dyeing with natural dyes which were economical, simply accessible in nature and sustainable. There is a great importance of this research in textile and clothing engineering since the task of dyeing the cotton fabrics with natural dyes were always challenging due to the poor colorfastness properties. Dyeing processes were conducted in textile mills and they involved the application of natural dyestuffs along with necessary chemicals and auxiliaries. The research may be considered important in textile wet processing zone since the dyeing of fabric with natural dyes can reduce the impact on the environment resulting from the disposal of toxic chemicals due to the application of ecofriendly substances. Different researcher worked related to this subjected matter at different times, where literature review exposed different results. For an example, due to the variety of variable involved, if one constraint was changed during experimentation, then there was also a change in the other property of fabrics, and this investigation was carried out with some substances obtained from nature. While experimenting with the cotton fabrics, it was observed that if one condition or amount of chemical or auxiliaries was changed, then there was an unexpected change occurred in the fabric’s color fastness properties or the fabric’s color staining properties [1]. Ford et al [2] reported that some dyestuff like indigo or lichen showed good color fastness property during dyeing. These dyes were known as direct dyes or substantive dyes since the majority of natural dyes necessitate the application of a mordant, which was applied to "fix" the color in the textile fibers. These dyes were also called sustainable dyes. These dyes were ecofriendly and did not do any harm to the environment. Kabir et al [3] reported that by applying various mordants with dyes, dyers can obtain outstanding colors and shades. Fibers or fabrics were treated with mordants and these mordants were integrated in the same dye bath [4]. In the customary dyeing process, the conjoint