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Bio-and Nanotechnology in the Processing of Silk
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Bio-and Nanotechnology in the Processing of Silk
In recent times there has been a renewed focus on environmentally friendly processes and chemicals. Standards such as Okotex 100, ISO 14,000 and GOTS have to be complied with to make the textile processors environmentally compliant. One must also comply with ISO 9,000 and SA 8,000 to be able to be acceptable in the International market. Moreover, it has become imperative for every industry to develop and adopt sustainable technologies in view of India signing Kyoto Protocol and committing to reduce its carbon dioxide emissions by 5.2 % during the first implementation period between 2008 and 2012. Sustainable technologies also require the use of renewable energy and raw materials to produce and process the products.
A large numbers of chemicals and dyes are used in the processing of textile fabrics and garments that require enormous energy for their application and remediation of the residual dyes and chemicals that end up in the effluent (Illustration I). Therefore the processed textile products have a heavy carbon footprint. The exporting countries increasingly want to know about the carbon footprints of the products that they source from India.
Advancement in the biotechnologies and their use in the processing of textiles has opened up new possibilities to enhance the sustainability credentials of textile industry since they are less energy intensive and generate bio-degradable effluent. This is true for silk processing where nano and biotechnology is beginning to find its application.
The major chemical processes that are carried out on raw silk yarn and fabrics are degumming, dyeing, printing and finishing.
Degumming
The silk filament spun by the silkworm (Bombyx mori) is composed of two fibroin filaments held together by a cementing layer of sericin. Fibroin and sericin account for about 75 wt% and 25 wt% of the raw silk, respectively. The degumming process consists in removing the sericin layer prior to dyeing or printing and finishing to get bright lustrous fabrics and garment. The degumming of silk has conventionally been carried out under alkaline conditions at a pH of 10 to 11 near boil. In recent years two new processes have emerged. They are the "H.T.-H.P. Degumming" and "Enzyme Degumming". High temperature high pressure degumming requires special pressured equipment and is energy-intensive process.
Enzymatic degumming is emerging as an eco-friendly fibre-gentle process where proteolytic enzymes that are effective under alkaline, neutral as well as acidic conditions are being used. With the local availability of the enzymes at a reasonable price this process has a commercial potential in India. Being large molecules, enzymes do not penetrate into the interstices of the fabric and hence are suitable for yarn degumming only. A critical control of the pH and temperature is required to realize the full potential of the enzymes requiring use of sophisticated machinery such as the Mezzera yarn-dyeing machine (Illustration II). Since most of the enzymes are effective at a comparatively low temperature of about 600C, they are less energy-intensive.
The degumming waste liquor that is rich in sericin content is being used as a raw material for the production of sericin powder. The sericin powder is being used in the cosmetic industry as moisturizer, in hair-care products and also as a sustainable natural textile finish (Illustration III). Removal of sericin from the waste degumming liquor also substantially reduces the effluent.
Source:
http://www.fibre2fashion.com/industry-article/16/1517/bio-and-nanotechnology-in-
