NIRJAFT

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CHEMICAL PROCESSING

Introduction

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Today, diversification of jute product has become essential as jute is emerging slowly but steadily for production of high value added decorative, furnishing textiles and even, to some extent, as apparels.  Therefore, bleaching, colouration and application of special finishes to impart its properties desirable for different end uses are essential.  This makes the wet chemical processing very important in modern jute industry.  Further, due to escalation of operational and energy cost in textile wet processing, simultaneous operation of several bath processes, cold wet processing, use of minimum application technology, reuse of dyes and chemicals etc. are becoming more effective.  Application of biotechnology by use of different enzyme on jute fabric produces fabric with improved feel, bleachability and dyeability character.  NIRJAFT has been working for a long time in the field of wet processing of jute.
 


Bleaching
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Bleaching is an important operation in the wet processing of jute fabrics to produce a creamy white shade.  Due to poor photo stability of jute, when exposed to light, the shade of bleached jute turns to brownish yellow colour in the long run.  The primary objective of jute bleaching is to improve its whiteness to a maximum extent with minimum loss in strength and weight and at the same time retention of whiteness for a longer period.

Bleaching of jute fabric can be carried out either by reducing method or by oxidising method. The bleaching effect is temporary if reducing method is used whereas it is long lasting if oxidising method is followed. Three most common oxidative bleaching process viz., (i) sodium hypochlorite bleaching (ii) sodium chlorite bleaching and (iii) hydrogen peroxide bleaching are studied, in depth.  It is found that the bleaching of grey jute fabric with sodium hypochlorite produce very poor whiteness while bleaching with sodium chlorite produced unsatisfactory whiteness with evnironmental hazards.  Only hydrogen peroxide bleaching is found to achieve satisfactory level of whiteness.
 


Dyeing
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Dyeing means an application of dyestuff solution through the entire length of the textile material in such a way that a uniform colour effect is produced.  Jute fibre, being lingo-cellulosic, has its potential of dyeing with all the dyes which are suitable for cotton dyeing.  Dyeing of jute with natural, direct, reactive, 1: 2 metal complex, basic, sulphur and vat dyes have been studied in detail.
 


Finishing
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Jute fibre has few deficiencies in properties like stiffness, drapability, abrasion resistance, dimensional stability, wrinkle resistance etc.  It has tendency to shed fibres, susceptible to fungal and microbial attack in humid condition.  The above drawbacks would not affect much for conventional use as packaging.  But in case of value added diversified products, it is essential to overcome above drawbacks to an acceptable limit by applying suitable finishes. Several finishing treatment like anti-crease finish, rot proofing finish, water repellent finish, anti fibre shedding finish and fire retardant finish were applied on jute fabric and their performance has been studied in detail.