Being a minor regional fibre with a share of less than 1%, silk has not had the benefit of R&D effort as much as other fibers have. R&D in the field of chemical processing of silk is confined largely to China, Japan, Italy and India. Como in Italy being one of the major processing centres for the silk fabrics with a dedicated research association in Milan. Likewise China has Suzhou Institute of Silk Technology; Shinshu University in Japan was a major research centre at one time. In India we have CSTRI in Bangalore and some universities and institutes doing R&D work in chemical 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.
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.