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Mechanical Properties and Stability to LightExposure for Dyed Egyptian Cotton Fabrics withNatural and Synthetic Dyes Kh. El-Nagar National Institute for Standards, Giza, Egypt Suzan H. Sanad and Amal S. Mohamed Cotton Research Institute—Agriculture Research Center,Giza, Egypt A. Ramadan Faculty of Applied Arts, Giza, Egypt Abstract: Synthetic dyes are more available than natural dyes were in the past,because of lower prices and wider ranges of bright shades with considerablyimproved color fastness properties. In current years, concern for the environmenthas created an increasing demand for natural dyes, which are friendlier to theenvironment than are synthetic dyes. The aim of this work is to study the effectof dyeing cotton fabrics with both a natural dye (henna) and a synthetic dye(Remazol blue) on some mechanical properties and those of stability to lightexposure. The undyed and dyed cotton fabrics were tested for their mechanicalbehaviors expressed as tenacity (N), elongation % , and work-breaking (N m).They were also tested for shrinkage and crease recovery angle. The stability tolight before and after 100h exposure was examined by investigating the micro-structure [using x-ray diffraction (XRD)] and macrostructure [using a scanningelectron microscope (SEM)] and the reflection spectra. The results proved thatthe cotton samples dyed with Henna dye have higher mechanical properties thanthose dyed with ‘‘Remazol’’ reactive dye. Moreover, the light fading behaviors of both synthetic and natural dyes were studied in terms of the reflection spectra(400–800nm), microstructure, and macrostructure of the sample’s fibers. Keywords: Henna, reactive dye, x-ray, SEM, cotton, macrostructureAddress correspondence to Kh. El-Nagar, National Institute for Standards,Giza, Egypt; E-mail: khnagare
[email protected] Polymer-Plastics Technology and Engineering , 44: 1269–1279, 2005Copyright Q Taylor & Francis, Inc.ISSN: 0360-2559 print/1525-6111 onlineDOI: 10.1080/03602550500207816 INTRODUCTION Natural dyes are fairly nonpolluting. They are very important for the his-torical textiles in the museums as well as to replace the synthetic dyes infood for safety and so forth [1] . They have also some disadvantages, only afew natured dyes have good fastness to light and washing [2,3] . Other dis-advantages include a lack of availability of precise technical knowledge of extraction and dyeing techniques, higher cost and limited range, andsome of mordants are harmful to silk.Henna is an excellent substantive dye that is made from Egyptian pri-vet (Lawsonia inermis), which has been used for centuries. The dye ismade from the dried leaves, which are picked, dried, and made into a pasteor powder containing hennatonic acid [4] . Tommasi isolated from hennaleaves a crystalline coloring matter, which was named lawsone, and hedescribed some of its chemical and physical properties [5] . He concludedthat lawsone is probably identical with 2-hydroxy-1,4 naphthoquinone.Lai and Dutt separated a compound from henna leaves, which was foundto be 2-hydroxy 1,4 naphthoquinone identical with that of Tommasi [6] .They also showed that lawsone behaves as an acid dyestuff and formsabout 1 % of the dry leaves. Cox analyzed a typical specimen of air-driedhenna leaves and found that it contained lawsone in a concentration of about 1 % , he found also that the dry leaf is free from starch and tannin [7] .On one hand, the major factors behind the remarkable growth of reactive dyes, which were introduced in 1956, are their specific properties,e.g., they can be applied to cotton by practically all known methods, theirhigh brilliancy of shades, and all round color fasteness for general useand universal application on pure and regenerated cellulose. On the otherhand, the main problem of these dyes is their light fastness propertieswhen compared with the other dyestuffs. These dyes form covalent link-age with the fiber substrate [8] .There are two purposes in the present study. Firstly, studying thephysical and mechanical properties of the cotton fabrics dyed with oneof the natural dyes (henna dye) and one of the synthetic dyes (Remazolblue reactive dye). Secondly, studying the stability of the dyes to lightexposure in terms of microstructure and macrostructure of the cottonfibers in the fabric. EXPERIMENTALMaterials One hundred percent Egyptian plain cotton fabric (Giza 83 and Giza 85varieties) were supplied by Misr Spinning and Weaving Company,El-Mahala El-Kubra from the 2001–2002 season. 1270 El-Nagar et al. Chemicals Disodium hydrogen phosphate, sodium dihydrogen phosphate, sodiumchloride, sodium carbonate, acetic acid, sodium hydroxide1, L-histidenmonohydrochloride, nonionic detergent, and copper sulfate were usedin this work (supplied by El-Gomheria Co., Egypt). Dyeing Method Dyeing with reactive dye (Remazol blue, supplied by Hoechst Company,Egypt) was carried out using 1 % reactive dye (dye = fabric weight) withliquor ratio 1:50 (fabric:solution). Inorganic salts and alkali were added,and the dyeings obtained were thoroughly washed with water, soapedwith a solution containing 2 % soap at 60 C, rinsed with water, and thendried at the ambient condition [9,10] . The natural dye was applied byimmersing the cotton fabrics in a dye bath containing the extract of henna (50 % –70 % ) at liquor ratio of 1:50mL dyeing solution for eachgram of the sample; copper sulfate was added as a mordant [11] . Measurements Tenacity (N), Elongation % and work-break of the preconditioned sam-ples (relative humidity of 65 5 % and temperature of 20 1 C) weremeasured using a Zwick automatic tensile testing machine, model 1511,Germany. The testing instrument was adjusted at speed of 100mm = min [12] . The obtained results and the average readings of 11independent measurements were statistically treated. Standard deviationand the uncertainty of the repeatability (U A ) were also calculated usingthe following equation [13] .UA ¼ Standard deviation = ffiffiffi n p where n is the number of measurementsThe shrinkage (dimension’s stability) of both dyed fabrics was testedusing a calibrated ruler according to the Kamat method [8] .Wrinkle recovery of the preconditioned samples (relative humidity of 65 5 % and temperature of 20 1 C) was measured in accordance withthe standard testing method [14] .Stability to light exposure before and after 100h exposure for undyedand dyed cotton fabric was examined by:1. The morphological investigations were carried out using a scanningelectron microscope (SEM) manufactured by Jeol Co., Japan. Thecotton fibers were deposited on the sample-holder, coated with a layer Dyed Egyptian Cotton Fabrics 1271 Table 1. Effect of dyeing with natural and synthetic dyes of the cotton fabric on the tenacity, elongation ( % ), and the work-break of the weftdirectionUndyed cotton fabric Fabric dyed with Remazol blue Fabric dyed with hennaSample no.Tenacity(N)Elong.( % )Work-break(N m)Tenacity(N)Elong.( % )Work-break(N m)Tenacity(N)Elong.( % )Work-break(N m)Average 491.2 3.8 4.3 421.5 4.8 4.2 462.8 5.1 4.8Standard deviation 27.9 0.3 0.6 29.2 0.2 0.5 4.2 0.4 0.4Uncertainty 11.4 0.1 0.3 11.9 0.1 0.2 1.7 0.1 0.1 1 2 7 2 Table 2. Effect of dyeing cotton fabric with natural and synthetic dyes on the tenacity, elongation ( % ), and the work-breaking of the warpdirectionUndyed cotton fabric Fabric dyed with Remazol blue Fabric dyed with hennaSample no.Tenacity(N)Elong.( % )Work-break(N m)Tenacity(N)Elong.( % )Work-break(N m)Tenacity(N)Elong.( % )Work-break(N m)Average 434.8 3.7 3.4 404.4 4.6 3.5 402.9 5.2 3.8Standard deviation 24.9 0.2 0.4 9.4 0.4 0.6 33.6 0.4 0.6Uncertainty 10.2 0.1 0.2 3.6 0.1 0.2 12.7 0.1 0.2 1 2 7 3
