Studies on the affinity of natural dyes on mulberry silk produced through different cocoon stifling methods
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Date
2024
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SKUAST Kashmir
Abstract
Silk has enthralled fashion industry and all categories of consumers across the world with its vast repertoire of motifs, techniques and brilliant hues. In the present study entitled ‘‘Studies on the affinity of natural dyes on mulberry silk produced through different cocoon stifling methods” rearing of bivoltine silkworm, Bombyx mori L. hybrid CSR2 x CSR4 was conducted at College of Temperate sericulture, Mirgund under standard recommended practice during spring 2022 and 2023. After harvesting, cocoons were stifled and dried which is an important step before these are processed for reeling as otherwise moth emergence renders these unfit for reeling as the continuity of the filament is broken in pierced cocoons. In the present study effect of various stifling methods viz., open sun drying method, sun drying with black cloth, Barrel steaming (Steam stifling) and Hot air oven drying method on the quality parameters of silkworm cocoons viz., average filament length, average non- breakable filament length, average denier, raw silk percentage, renditta and reelability percentage was studied. The cocoon dried by hot air-drying method showed significantly higher average filament length (1138.02m) and higher non-breakable filament with a value of 817.34 m as compared to all other treatments. Non- significant difference in overall denier among all the experimental treatments was observed. The best renditta was recorded in hot air drying with a value of 6.64. The raw silk percentage and reelability percentage of cocoons dried under hot air-drying method showed significantly higher percentage of 39.50% and 84.78 % respectively compared to other treatments. Thus, stifling of cocoons with hot air-drying method showed cocoon characteristics significantly better as compared to other stifling methods. Exposure of cocoons to direct sunlight deteriorates the quality of the cocoons. All above parameters were observed inferior in open sun drying method of stifling and drying
Textile industry at present uses excessive amount of synthetic dyes to meet the required coloration for global consumption of textiles due to cheaper prices, wider ranges of bright shades, and considerably improved fastness properties in comparison to natural dyes. The application of such dyes causes serious health hazards and influences negatively the eco-balance of nature. As a result, natural dyes are among the promising options for developing a greener textile dyeing process. Natural dyes are non-carcinogenic, produce soothing and exclusive color to the textiles, and have better biodegradability and higher compatibility with the environment. Three natural dyes viz., Henna leaves (15%), Beetroot peel (10%) and cockscomb flowers (10%) and two mordants i.e., ferrous sulphate (3%) and Alum (3%) were used for the present study. The extracted natural dyes were applied on silk obtained through different stifling methods adopting different mordanting methods, including and excluding a mordant. Dyed fibres were assessed for percent absorption, colour coordinates of dyed fibres, colour strength (K/S) and colour fastness to washing, light and rubbing. Percent dye absorption of all natural dyes recorded satisfactory results. Stifling methods and mordanting methods adopted recorded significant variation in percent absorption. Mordanted samples showed better percent dye absorption than the un-mordanted samples. The highest percent dye absorption (78.73±3.43) was recorded in open sun drying with black cloth at post mordanting method in henna dye. In beetroot dye, Barrel steaming recorded highest (87.65±0.46) dye absorption value at simultaneous mordanting method. Cockscomb recorded highest percent absorption (92.42±0.84) in hot air drying at post mordanting method. Post mordanting recorded highest percent absorption in henna and cockscomb dyes and simultaneous mordanting in beetroot dye. The colourimetric values of dyed fibres differ significantly with varying shades and colour tones due to different type of fibres and mordanting methods. Dyed fibres were endowed with very good dye adherence as seen from L*, a*, b*, C*, h0, ∆E and K/S values All the treatments within all the groups of ∆E showed significant difference among each other in all the natural dyes. In henna, the highest ∆E (64.66±3.85) was recorded in barrel steaming at simultaneous mordanting method. In beetroot, the highest ∆E (32.46±1.65) was recorded in open sun drying with black cloth at pre-mordanting method. In cockscomb, the highest ∆E (38.27±1.19) was recorded in open sun drying at post mordanting method. The highest colour strength value (3.76± 0.52) was recorded in simultaneous mordanting method in henna. In beetroot, the highest K/S value (0.44±0.08) was recorded in post mordanting method. In cockscomb, the highest K/S value (1.15±0.20) was recorded in post mordanting method. All the dyes, stifling methods and mordanting methods recorded acceptable fastness grades. Stifling methods and mordanting methods showed significant results of washing fastness, light fastness and rubbing fastness properties. Mordanting Methods adopted showed significant difference in fastness properties. The un-mordanted samples showed Fair to Good (3/4) to Excellent (5) grades with different dyes whereas the mordanted samples recorded good (4) to Excellent (5) grades in majority of the combination of stifling methods and mordanting methods. The post mordanting method recorded satisfactory grades with majority of the fibres obtained through different stifling methods followed by simultaneous mordanting and pre mordanting methods. All the selected dyes and mordants can be used as an alternative for synthetic dyes which are carcinogenic and banned in majority of countries of the world. These natural dyes and mordants are recommended as commercial viable sources for the dyeing of silk fibres.
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Keywords
Stifling, Cocoons, Ecofriendly Natural dyes, Silk, Mordant, Sericulture