By: Dr. S.N. Chattopadhyay, Dr. N.C. Pan and Dr. A.K. Roy


Golden fibre, jute, is now being utilized for a number of value added and diversified products as it has not lost its glitter. Traditional use of jute fabric i.e., sacking and hessian will continue for its use as packaging material, carpet backing, etc. Non traditional use in curtains, upholstery, furnishing textiles and apparel textiles will increase gradually due to its eco-friendly and biodegradable character. So, modification of feel and look of the fabric has become essential depending on the end use requirement resulting in increasing the demand for bright, wash fast and light fast jute fabric.


Chemical composition of jute is complex. It contains cellulose, hemicellulose and lignin as the major constituent. So, chemical processing of jute is delicate as severe treatment may cause damage to the fabric. This fibre is very sensitive to alkali due to the presence of hemicellulose and the presence of cellulose makes it sensitive to strong acid. At every stage of chemical processing, a com promising recipe is to be formulated which produces acceptable result retaining sufficient physical properties.


First step of dyeing of jute fabric is known as preparatory process where fibre is made clean by removing its natural and added impurities which is known as scouring. Proper scouring is the basic requirement for even dyeing.


The next step is bleaching. By this process, the fabric is made white by removing or modifying the colouring matter present in the fibre. The main colouring matter in jute fibre being lignin, which also acts as cementing material and contributes to the strength of the fibre.


Table 1: Preparatory processing of jute fabric

Process

Chemicals used

Results

Scouring

Sodium carbonate / sodium hydroxide and non-ionic detergent

Removes natural and added impurities like sizing materials, fats, oil and waxes to make the fabric more absorbent.

Bleaching

Hydrogen peroxide, sodium silicate, sodium hydroxide and non-ionic detergent

It modifies the colouring matter present in the fabric and produce white fabric.

  • Full bleach - Full white, sold as bleached fabric
  • Half bleach - For pale and medium shade dyeing
  • Quarter bleach - For deep shade dyeing


For deep shade mild bleaching is sufficient but for producing light and pale shade full bleach is needed. Depending on the shades to be produced, the method of bleaching as well as bleaching agent can be selected. Different oxidizing and reducing agents can be utilized for bleaching of jute fabric and among them hydrogen peroxide, a non-chlorine oxidative bleaching agent, is the most popular.


The bleached fabric thus produced is ready for dyeing. All the dyes that are suitable for dyeing of cellulosic fibre can be applied for dyeing of jute fabric as cellulose is the main constituents which take part in the dyeing process.