**4. Conclusions**

The feasibility of using a reducing system based on sodium borohydride and sodium bisulphite to apply vat dyes to wool has been demonstrated. For a range of nine vat dyes, better colour yields and overall better fastness properties were obtained by the

**1. Introduction** 

**3** 

*India* 

**Pretreatments of Textiles** 

R. R. Deshmukh1 and N. V. Bhat2

*N. Parekh Marg, Matunga, Mumbai, 2Bombay Textile Research Association, LBS Marg, Ghatkopar (w), Mumbai,* 

**Prior to Dyeing: Plasma Processing** 

Synthetic fibres have acquired an important part of the current textile industry. A great disadvantage of some of the synthetic fibres is their low surface energy. This causes poor wettability and dyeability. Surface modification techniques are mainly carried out to remove loosely bound materials, foreign particles/impurities and to improve hydrophilic nature and thereby improving dyeability. Manipulation of surface characteristics of textile materials is of fundamental importance in the production of advanced functional textiles. Textile fibres can be classified in two main groups: Natural and Synthetic. Natural fibres are of animal origin or plant origin such as silk, wool, hair, jute, cotton, cellulose etc. whereas there are a number of manmade/synthetic fibres such as viscose, polyester, polypropylene, nylon, PLA fibres, polyamide and acrylic fibres. Natural fibres are limited and are not sufficient and not always suitable for many applications. Hence synthetic fibres have acquired greater importance in the present era. Synthetic fibres form an important part of the textile industry, with the production of polyester alone surpassing that of cotton. Improving the surface properties suitably is a very important aspect of the textile processing. Low surface energy of the synthetic fibres affects the processing of the fibres, especially during wet treatments. The surfaces are not easily wetted, thus impeding the application of finishing compound and colouring agents. In addition, a hydrophobic polymer hinders water from penetrating into the pores of the fabric. For a number of applications it is necessary to modify surface properties of textiles from hydrophobic to hydrophilic and vice versa. Plasma processing has a potential to render and change such surface properties. Recent advances in textile chemistry have resulted in imparting various functional properties such as decreased skin irritations, enhancing antimicrobial activity and fragrance to the textile material. The surface composition and structure of a textile material plays an important role in the textile's performance in specific applications. E.g. The surface of apparel / textile garment that is in contact with human skin could be modified to absorb the body moisture while the outside surface could be modified to repel water. Several studies showed that properties of polymeric substrates could be altered through surface modification (Deshmukh and Bhat, 2003 (a); Deshmukh and Shetty, 2007; Jahagirdar and

Tiwari, 2004; Navaneetha P., et al., 2009; Yen et al., 2006).

*1Physics Department, Institute of Chemical Technology,* 

borohydride/bisulphite method, compared with the conventional procedure involving sodium hydrosulphite/NaOH. Furthermore, the SBH/bisulphite procedure produced less fibre damage than the conventional method.

Sodium borohydride is more expensive than sodium hydrosulphite. However, the cost difference between the auxiliaries is likely to be offset by the better colour yield and, for an expensive substrate such as wool, by the lower fibre damage produced by the SBH/bisulphite reducing system, compared with sodium hydrosulphite/NaOH.
