Abstract
The great appeal of textiles lies in their colours and the way that colour is used to create patterned effects. Colour is applied by the process of dyeing, which in its simplest form involves the immersion of a fabric in a solution of a dyestuff in water.
The amount of dyestuff required is very small, but its production and application require considerable skill. Changes in the ways of producing dyes during the nineteenth century heralded modern science. The uses of natural dye on textile materials are now being popularised globally by the continuous efforts of nature lovers. The problems caused by synthetic dye in human lives and environments, since the introduction of synthetic dye more than a century ago, has come to an alarming level today. Hence there is an urgent need to for an alternative to the hazards of synthetic dyes.
To explore the use of natural dyes is one such immediate solution. However, the limitations with the natural dye are their poor fastness properties, limited shades, low brilliancy, etc. To some extent, adding selected mordants/chemicals in natural dyeing is accepted, provided the character of the natural dye is unaltered and the eco-system is not damaged.
The present study explored the development of a process for the extraction of natural dyes from abundantly occurring plants, flowers namely Croton (Croton species) leaves. The study showed that this source can produce different shades of brown and peach colour. A series of experiments was conducted to optimise the different variables for dyeing. Acidic medium was optimised for dye extraction. For Croton dye, 8% dye concentration, 60 minutes extraction time and 75 minutes dyeing time were optimised.
Test of colour fastness to light, washing, perspiration and crocking were also carried out. The results concluded that the light fastness, washing, fastness, perspiration and crocking fastness of the Croton dye were good and samples that were mordanted showed better fastness properties as compared to control. This dye source is abundantly available throughout the year and does not cause environmental depletion. Experiments proved that the Croton dye is the good source for dyeing silk in shades of brown and peach. Thus it can be concluded that this dye has a lot of commercial potential.
Introduction
The use of natural dyes has attracted increasing worldwide attention as the carcinogenicity and environmental pollution problem of synthetic pigments are becomes a great concern.
Increased environmental awareness and health hazards associated with the use of synthetic dyes have led to the revival of natural dyes.
Natural dyes are eco-friendly and promote the green revolution. It is the need of the day to exploit the forest wealth that can be a source of colour for textiles.
Natural dyes are deep and soft in colour, and many of these have antibacterial, insecticidal and medicinal properties, due to their natural origin, from herbal plants. Most of the natural dyes are non-substantive dyes, as they require the aid of mordants to penetrate the yarn/fibres.
Croton (Croton species) leaves come from one of the most colourful evergreen shrubs that we grow indoors. Also known as Codiaeum, this plant has its origin in Malaysia and the larger islands in the West Pacific. It is grown for its decorative foliage. The leaves are alternate, linear to broadly ovate, simple or shallowly to deeply lobed, and often variegated. They reach all the possible colours that a leaf can be, from the brightest green and yellow to the deepest green and red. Foliage colours change as the plant matures. There are never two leaves that look the same on a plant, and this is why Croton is so attractive.
In the present era the revival of natural dyes has created opportunities for researcher to explore for alternative sources that can compete with synthetic dyes in brilliant colour fastness.
Keeping these points in mind, an attempt was made through this study to optimise various dyeing variables for dyeing of silk fabric with Croton dye and also to test the colour fastness of dyed samples.
Experimental Procedure
Selection of Fabric
Silk (garad) fabric was selected for the study, as this fabric gave brilliant shades with selected dyes.
Pretreatment of Silk
A mild detergent (genteel) solution containing 0.5 ml of genteel/100 ml of water was prepared and heated to 50°C. Silk fabric was dipped in to this solution and stirred gently for about 30 min, then it was rinsed under tap water and dried in shade and ironed when half wet.
Selection of Dye
Croton (Croton species) leaves were selected for the study. The leaves were dried in shade.
Selection of Mordants
Three metallic mordants, viz. potassium aluminium sulphate (alum), copper sulphate and ferrous sulphate, and three natural mordants, namely bahera, pomegranate rind and tea leaves, were taken for study.
For each mordant, four concentrations – ie.0.5, 0.10, 0.15 and 0.20gm for alum; 0.1, 0.2, 0.3 and 0.4gm for copper sulphate and ferrous sulphate; and 1, 2, 3 and 4gm for bahera, pomegranate rind and tea leaves – were used. Three methods of mordanting, viz. pre-, simultaneous and post-mordanting were used for the study.
Optimisation of Dyeing Variables
A series of following experiments were conducted to determine the dyeing variables such as extraction medium, optimum concentration of dye material, extraction time, and dyeing time, concentration of mordants and methods of mordanting.
Medium of Extraction for Dyeing
Dye from Croton was extracted in alkaline, acidic and aqueous medium. Acidic medium was prepared by adding 1ml of hydrochloric acid in 100ml of water and alkaline medium was prepared by adding 1gm of sodium carbonate in 100ml of water. The dye material was then entered in each solution and boiled at 60°C for 1 hour. For aqueous medium only dye material was added in 100ml of water. To each dye extract, a known amount of silk fabric introduced and dyeing was carried out for 60 minutes. The method that gave the best colour on the silk was selected for further study.
Concentration of Dye Material
Five different concentration of dye material were prepared separately by heating 2, 4, 6, 8 and10gm of dye material in 100ml of water at 80°C for 1 hour. The solution were filtered and cooled.
The optical density (OD) of the dye solution before and after dyeing was recorded and the percent absorption was calculated by using following formula:
Percent absorption = Optical density before dyeing - optical density after dyeing/Optical density before dyeing X100
The concentration that showed the highest percent absorption was selected as the optimum concentration for further study.
Time for Extraction of Dye
The selected concentration of dye material was taken in five beakers, each containing 100ml of acidic water and boiled for 30, 45, 60, 75 and 90min respectively. To each extracted solution, known weights of silk fabric were introduced and dyed for 60 minutes. The dyed fabrics were removed from the dye liquor, and dried in shade. Percent absorption was calculated for each sample and, on the basis of results, time for dye extraction was optimised.
Dyeing Time
Five dye solutions of Croton leaves were prepared by extracting dye using the optimum dye concentration and extraction time in 100ml of water. Dyeing of pre-soaked silk samples was carried out for 30, 45, 60, 75 and 90 minutes respectively.
Percent absorption by each sample at different dying times was calculated. Based on maximum percent absorption, the best dying time was optimised.
Preparation of Blank Sample
After optimising the dying variables, a known amount of silk fabric was dyed with the optimum concentration of dye, extraction time and dying time.
Colour Fastness Testing
Each dyed sample was tested for colour fastness against light, washing, rubbing and perspiration. Light fastness testing was carried out according to the ISI: 971-1156 Test method; the washing fastness test was carried out as per recommendations of ISI test no.3; fastness against rubbing was determined using AATCC test method; perspiration fastness testing was carried out according to ISI: 971-1156 test method.
Results and Discussion
Medium of Extraction of Croton Dye
Among three media of dye extraction, ie. acidic, alkaline and aqueous, acidic medium was selected as the best. Dye extracted with 1% hydrochloric acid was selected for dye extraction.
Dye Concentration
Silk fabric was dyed with five different concentrations of Croton dye, ie. 2, 4, 6, 8 and 10%. The maximum percent absorption was obtained with 8gm dye material/100ml of water/2gm of silk. Results are shown in Table 1.
Dye Extraction and Dyeing Time
The dye was extracted and dyed at 30, 45, 60, 75 and 90 min. Maximum percent absorption was obtained at 60 minutes for extraction and 75 minutes for dyeing. Therefore 60 and 75 minutes were selected as optimum for extraction and dyeing time respectively. Results are shown in Table 2.
Concentration of Mordants
Synthetic Mordants
It was found that out of the various concentration of mordants used with Croton dye, best shades of colour were obtained by using 0.05gm (pre-mordanting), 0.10gm (simultaneous mordanting) and 0.15gm (post-mordanting) of alum; 0.02gm (premordanting), 0.01gm (simultaneous mordanting) and 0.04gm (post-mordanting) of copper sulphate; and 0.02gm (pre- and postmordanting) and 0.01gm (simultaneous mordanting) of ferrous sulphate.
Natural Mordants
For Croton dye the concentration found best for different natural mordants were: bahera 01gm (pre-mordanting) and 03gm (simultaneous and post-mordanting); pomegranate rind 04gm (pre-mordanting), 01gm (simultaneous mordanting) and 04gm (post-mordanting); and tea leaves, 02gm (pre-mordanting and simultaneous mordanting) and 01gm (post-mordanting). (Table 3)
Colour Fastness
Colour fastness grades of silk samples dyed with Croton dye using different concentration of each mordants and three mordanting methods are given in Table 4.
The results given in the table reveal that the light-fastness grade ranged between poor (2) and good (5).
Washing fastness tests revealed that silk samples dyed with Croton dye showed considerable to slight colour change (2-4) and slight to no staining (4-5). Colour fastness grades were maximum in the case of all mordants. Ferrous sulphate and tea leaves gave better washing fastness.
Perspiration fastness grades for all the mordants were showed slight to negligible colour change (4-5) in acidic medium, whereas considerable to slight change (2-4) in colour was found in alkaline medium. Metallic mordants showed better perspiration fastness than natural mordants.
In crocking fastness, it was found that wet crocking ranged from slight to no staining (4-5) for samples mordanted with metallic mordants. In the case of natural mordants it ranged from noticeable to no staining (3-5). There was no change in colour in both dry and wet crocking.
Conclusion
Croton dye is a good source of pinkish brown (peach) colour and it creates a number of fast shades, ranging from brown, grey, green and khaki, on silk by using different natural and metallic mordants.
Researchers and scientists have a good opportunity to make a pollution-free environment by using this source on textile material, as the processing of these dyes involved no toxic chemical.
A wide range of colours and satisfactory fastness to light, washing, perspiration and crocking were obtained on silk.
Finally, it can be concluded that the application of Croton-leaf dye for dying of silk can be considered as an effective eco-option for protection of our environment and can be commercialised.
References
1. Bello, K.A and Defeng, Z.1999 Dye and intermediate. The Indian Textile journal 10(10) : 42
2. Das, S. 1992. Application of natural dye on silk, Colourage, 32 (9) 152
3. Gulrajani M.L 1993 Mordant compendium of inter regional workshop on natural dyes. Lucknow NHDC Ltd; pp 96-103.
4. Patra, S.K.; Nayak, A. and Das, N.B.2000. Yellow dye from debarked jack fruit wood. Colourage, 17 (8): 17
5. Paliwal, J. 2001. Effects of mordants on henna dyed cotton and silk fabric. Textile Magazine, 42 (11): 79.
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