The Influence of Mordanting on the Dyeability of Cotton Dyed 199 with Turmeric Extract Irena Mulec and Marija Gorjanc University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Textiles, Graphic Arts and Design, Snežniška ulica 5, SI-1000 Ljubljana The Influence of Mordanting on the Dyeability of Cotton Dyed with Turmeric Extract Vpliv čimžanja na obarvljivost bombaža z ekstraktom kurkume Original Scientific Article/Izvirni znanstveni članek Received/Prispelo 04-2015 • Accepted/ Sprejeto 07-2015 Abstract The dyeability of cotton fabric with turmeric extract in two concentrations (pale and dark dyeing) was studied using four different mordants in low concentration (0.2 g/l). As mordants three metal salts were used as mordants (ferrous sulphate, aluminium sulphate and zinc chloride), and organic mordant tannin. The mordanting of cotton was performed before, during and after dyeing, namely by pre-, meta-, and post-mordanting application methods. Colour fastness of dyed samples to repetitive washing and hot pressing was also performed. The colour values of the dyed samples were measured on a reflectance spectrophotometer. The results showed that the dyeability of the cotton with turmeric extract is greatly influenced by the used mordant and its application method. The highest dyeing uptake (dyeability) was achieved by pre-mordanting with aluminium sulphate. All the mordanted samples had improved colour fastness, especially those samples meta-mordanted with ferrous sulphate. Keywords: cotton, turmeric, curcuma, mordant, natural dyeing, dyeability Izvleček V raziskavi je bil proučevan vpliv čimžanja z uporabo štirih čimž v nizki koncentraciji (0,2 g/l) na obarvljivost bombažne tkanine z ekstraktom kurkume v dveh koncentracijah (za svetlo in temno obarvanje). Uporabljene čimže so bile tri kovinske soli (železov sulfat, aluminijev sulfat in cinkov klorid) in organska čimža tanin. Čimžanje je potekalo pred barvanjem, med njim in po njem oziroma pre-, meta- in postčimžanje. Določene so bile tudi barvne obstojnosti na večkratno pranje in vroče likanje. Barvne vrednosti barvanih vzorcev so bile določene z uporabo refleksijskega spektrofotometra. Raziskava je pokazala, da je obarvljivost bombaža z ekstraktom kurkume močno odvisna od uporabljene čimže in načina čimžanja. Najgloblje obarvanje je bilo doseženo pri bombažu, bar-vanem z višjo koncentracijo ekstrakta kurkume, ki je bil čimžan z aluminijevim sulfatom pred barvanjem. Barvne obstojnosti na pranje in vroče likanje so se z uporabo čimž na splošno izboljšale, najbolj za vzorec, metačimžan z železovim sulfatom. Ključne besede: bombaž, kurkuma, čimža, barvanje z naravnimi barvili, obarvljivost 1 Introduction Textile materials are usually dyed using synthetic dyes. Synthetic dyes are used in order to facilitate the high demands of the costumers and the added-value of the textile material [1]. The high usage of Corresponding author/ KorespondenCna avtorica: Assist. Prof. D.Sc. Marija Gorjanc Telephone: +386 1 2003256 E-mail: marija.gorjanc@ntf.uni-lj.si synthetic dyes in textile dyeing is also due to their ready-to-use form for fast and easier handling and repeatability of dyeing. Over recent years we have witnessed an immense shift towards the usages of natural dyes and pigments during the dyeing and printing of textile materials due to, again, costumer Tekstilec, 2015, letn. 58(3), str. 199-208 DOI: 10.14502/Tekstilec2015.58.199-208 200 The Influence of Mordanting on the Dyeability of Cotton Dyed with Turmeric Extract demand. Costumers are becoming more and more conscious about the hazardous threats and potential health issues in conjunction with the textiles they are using. Most of the commercial textile dyers have responded to the trend towards using natural dyes and started looking towards the maximum possibilities of using natural dyes for the dyeing and printing of different textile materials [1, 2]. For a successful commercial use of natural dyes for any type of textile, the appropriate and standardised techniques of dyeing need to be adopted [1]. The word 'natural dye' covers all those dyes derived from natural sources such as plants, animals, and minerals [3]. Natural dyes produce very lustrous, soft and soothing shades as compared to synthetic dyes [1]. Natural dyes are more eco-friendly, can perform better biodegradability and generally have a higher compatibility with the environment. Furthermore, natural dyed textiles also have good UV-protection and antibacterial activity [4, 2]. Turmeric is the most popular natural dye in textile dyeing [1]. Turmeric is a rich source of phenolic compounds called curcuminoids [5]. The active colouring ingredient in turmeric rhizome is Curcumin, which is also known as Natural Yellow 3 (C.I. 75300). Its general formula is given in Figure 1. Figure 1: Chemical structure of turmeric (keto form) [5] Turmeric is the brightest yellow natural dye, which belongs to the diaroylmethane group named difer-uloylemethane [5]. It is also well-known for its anti-carcinogenic, anti-inflammatory, anti-microbi-al, anti-parasitic, anti-mutagenic and anti-inceptive properties, as well as for the formation of sunscreen products [6-8]. Natural dyes such as turmeric dye are mostly non-substantive and must be applied on textiles with the help of mordants, usually a metallic salt, having an affinity for both the dye and the fibre [9]. Metallic mordants are generally metal salts of aluminium, iron, copper, chromium and tin [1]. The metallic mordants are of two types. Brightening and dulling mordants. Amongst all types of aluminium, potash aluminium is a cheap, easily available and safe to use mordant. It usually produces pale versions of the prevailing dye colour in the plant. Chrome is also referred to as red chromate but it is relatively more expensive. However it is considered to be harmful for human skin. Copper is known as blue vitriol, it is readily soluble in water and easy to apply. It gives some special effects in shades that otherwise cannot be obtained. However, copper beyond a certain limit is also under the eco-standard norms as objectionable heavy metals. Iron is also known as green vitriol and is readily soluble in water. It is used for darkening, browning and blackening of the colours / shades. It is easily available and one of the older mordants known. It is extensively used to get grey to black shades. Tanin is not a metal salt but it gives brighter colours than any other mordant. However, the tannin mordant is oxidised on exposure to air and imparts a stiff hand to the fabric if used in high concentration [1]. Zinc is a slightly acid mordant of white powder or silver-grey metallic granules with a 4.5 pH, easily clumped by humidity; found naturally, known since at least around 15 th century. Natural and man-made fibres can be dyed with turmeric extract dye. Turmeric extract can be applied onto cotton, silk, polyamide and acrylic fibres [1, 2, 6, 10, 11]. Different mordants on acrylic fibres not only cause difference in hue and changes in K/S values but also changes in colour characteristic when dyed with turmeric extract [6]. Hydroxylamine hydrochloride and ammonium acetate were used for providing higher concentration of the nitrogen on the surfaces of acrylic fibres. The K/S values of the dyed samples were higher due to the increased nitrogen content on the fibres. The washing, perspiration, and rubbing fastness properties for the dyed samples were enhanced by application of alum as pre-mordant. A man-made fibre that also contains nitrogen in its structure is polyamide [11]. Polyamide samples were pre-mordanted with potassium aluminium sulphate, cupric sulphate, ferric sulphate and dyed with turmeric extract at 100°C. The results showed that using mordants leads to higher K/S values, for example ferric sulphate mordant gave the highest K/S value [11]. Another nitrogen containing fibre is silk, which is a natural protein fibre and was dyed with turmeric after mordanting with copper sulphate, ferrous sulphate and potassium aluminium sulphate [10]. The results showed that pre-mordanting of silk imparted deeper shades compared to the fabrics dyed without mordants. Cotton is also a natural fibre, however it Tekstilec, 2015, letn. 58(3), str. 199-208 The Influence of Mordanting on the Dyeability of Cotton Dyed 201 with Turmeric Extract does not contain nitrogen within its structure and for the purpose of dyeing with natural dyes needs to be mordanted. Pre- and post-mordanting with iron and aluminium improves the light fastness and washing fastness of turmeric dye on cotton [12]. In previous studies of dyeing textiles with turmeric dye, mordants were applied onto textiles mostly before dyeing (pre-mordanting) and at high concentrations. The purpose of our research was to dye cotton fabric with turmeric extract, using low concentrations of different mordants and different mordanting application methods, i.e. mordanting prior, during and after dyeing, and to evaluate which mordanting technique gives higher dyeability with turmeric. 2 Experimental Material 100% bleached cotton plain weaved fabric (Teksti-na, Ajdovščina) was used for the research. Mordanting Ferrous sulphate (FeSO4), aluminium sulphate (Al2(SO4)3, zinc chloride (ZnCl2) and tannin were used as mordants. The application methods of mordanting were pre-mordanting (mordanting before dyeing), meta-mordanting (mordanting during dyeing) and post-mordanting (mordanting after dyeing). The concentration of mordant was 0.2 g/l. Pre-and post-mordanting was performed at goods to liquor ratio 1:40 for 10 min at room temperature. The samples were then dried in the oven at 130°C, for 5 min. Meta-mordanting was performed during dyeing. Extraction of turmeric dye The dye was prepared by extracting turmeric powder from deionised water at neutral pH, at 95°C for 1.5 hours. Two concentrations of turmeric powder were used, i.e. 2 g/l and 20 g /l. The obtained Curcuma Longa extract solution (dye solution) had a yellowish colour. Wash-fastness The dyed samples were washed in the Launderome-ter Laboratory apparatus according to EN ISO 105-C06 standard. The size of the sample was 100 x 40 mm, the wash bath contained 4 g/l ECE phosphate reference detergent B, the volume of the bath was 150 ml, the temperature of the bath was 40°C and time of washing 45 minutes. Ten stainless steel globules were added into each bath to perform washing, which corresponds to five domestic washings. After washing, the samples were rinsed twice in deionised water and air dried at room temperature. Fastness to hot pressing Hot pressing of dyed samples was performed according to EN ISO 105-X11standard. The test specimen and adjacent fabric were soaked in distilled water and squeezed. The wet specimen and adjacent fabric were placed on the top of dry adjacent fabric. The specimen was put into a heating device for 15 s at 200 ± 2°C. Fastness was evaluated according to the Grey Scale test (standards EN ISO 105-A05 and EN ISO 105-A04). Colour measurements CIE L*a*b* colour values and reflectance (R) of samples were measured using a reflectance spectrophotometer Spectraflash 600 PLUS-CT (Datacolor). From the CIE L*a*b* colour values, colour differences were calculated according to equation 1: AEab* = )+L*2 + A a*2 + A**2, (1) where AL* is the lightness difference, Aa* is the red/ green difference and Ab* is the yellow/blue difference between standard and batch. From the reflectance measurements, K/S values were calculated according to equation 2: K = (1 - R) S 2 R (2) where R is the reflectance, K is absorbance and S is the scattering. Dyeing Dyeing of cotton was performed in stainless-steal beakers, at goods to liquor ratio 1:40, at 60°C, for 60 min. After dyeing, rinsing of samples was performed in warm and cold deionised water. The samples were air-dried at room temperature. 3 Results and discussion The CIE L*a*b* colour values of the non-dyed non-mordanted sample (UN) and samples mordanted with FeSO4 (Fe), Al2(SO4)3 (Al), ZnCl2 (Zn) and Tekstilec, 2015, letn. 58(3), str. 199-208 202 The Influence of Mordanting on the Dyeability of Cotton Dyed with Turmeric Extract tannin (Tan) are presented in Table 1. The results show that mordanting with FeSO4 caused the non-dyed sample to be darker, redder and yellower compared to the non-mordanted non-dyed sample. Mordanting with Al2(SO4)3 and ZnCl2 caused the samples to be greener and yellower compared to the non-mordanted sample. Mordanting with tannin caused the sample to be darker, greener and e yellower compared to the non-treated sample. From the results of colour differences (AE*ab) between non-mordanted and mordanted non-dyed samples (Figure 2) it is clear that mordanting with Al2(SO4)3 and ZnCl2 does not induce colour changes. The AE*ab values were lower than 1, meaning that colour change was undetectable (there was no visible colour difference between the samples) [13]. Mordanting with FeSO4 and tannin gave the AE*ab values 8.45 and 3.52, respectively, meaning that the colour change was detectable. Table 1: CIEL* a*b* colour values of non-mordanted (UN) and mordanted non-dyed samples Sample L* a* b* UN 95.37 -0.21 1.84 Fe 91.98 0.05 9.58 Zn 95.30 -0.45 2.24 Al 95.24 -0.41 2.17 Tan 93.82 -0.49 4.99 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 _ _ I Zn Al Sample Tan Figure 2: Colour differences (AE*ab) between non-mordanted and mordanted non-dyed samples From the results of mordanting non-dyed cotton it could be assumed how mordanting would affect dyeing with turmeric extract, i.e. mordanting with FeSO4 and tannin would give predominantly darker, redder (or greener) and yellower dyeing and that mordanting with Al2(SO4)3 and ZnCl2 would not affect the colour differences significantly. However, the results of cotton dyed with turmeric extract show a different trend. In Table 2, the results of CIE L*a*b* values are presented for cotton samples dyed with 2 g/l of turmeric extract. Mordanting with FeSO4 indeed caused the dyed samples to be darker, however the samples were less yellow (Table 2). Furthermore, the mordanting application method with FeSO4 had a great influence on the final colour values of the dyed samples. For example, pre-mordanting gave darker, less green and less yellow dyeing while meta and post-mordanting gave darker, redder and less yellow dyeing compared to the non-mordanted dyed sample. The mordanting application method also influenced when other mordants are used (Table 2). The meta-mor-danted ZnCl2 samples were yellower compared to the non-mordanted sample. The pre- and post-mordanted ZnCl2 samples were lighter, greener and yellower than the non-mordanted dyed sample. Pre-mordant-ing with Al2(SO4)3 gave lighter, greener and less yellow dyeing, meta-mordanting gave lighter, less green and yellower dyeing and post-mordanting gave lighter, greener and yellower dyeing compared to the non-mordanted dyed sample. Dyeing of samples mordanted with tannin gave similar CIE L*a*b* colour values Table 2: CIE L*a*b* colour values of non-mordanted (UN) and mordanted samples dyed with 2 g/l of turmeric extract Sample L* a* b* UN 90.98 -5.32 61.64 Pre_Fe 84.11 -1.28 46.17 Meta_Fe 83.22 0.50 32.03 Post_Fe 82.10 1.90 45.81 Pre_Zn 91.48 -5.71 62.90 Meta_Zn 90.19 -4.77 64.64 Post_Zn 92.06 -6.30 62.74 Pre_Al 91.34 -6.36 57.12 Meta_Al 91.08 -4.52 61.93 Post_Al 91.74 -6.60 64.23 Pre_Tan 90.35 -5.36 62.82 Meta_Tan 90.00 -5.76 62.33 Post_Tan 90.82 -5.91 61.74 Tekstilec, 2015, letn. 58(3), str. 199-208 The Influence of Mordanting on the Dyeability of Cotton Dyed 203 with Turmeric Extract 35.00 30.00 25.00 .q 20.00 (C &U < 15.00 10.00 5.00 0.00 V .0/ &•/ .0/ JS/ &■/ i ^