Abstract

Introduction

Non-woven fabric is manufactured by putting small fibers together inthe form of a sheet, and then binding them either with chemical, thermal ormechanical bonding to form a fabric. These fabrics are not strong unlessreinforced by a backing and do not stretch. Non-woven materials are mainlyproduced from manmade fibers viz., rayon, polypropylene and polyestersand used in areas like hygiene (baby diapers, feminine hygiene and adult incontinenceproducts, wipes, bandages and wound dressings); medical (isolation and surgicalgowns, drapes, covers, scrub suits and caps); technical (wall coverings,electric insulation, insulation backing, circuit board reinforcement); filters(gasoline, oil, air, water, coffee, tea bags) and others (carpets, pillows,cushions, upholstery padding, consumer and medical facemasks).

In India, the non-woven industry is evolving. As the price of petro-based materials like polypropylene and polyester continues to be high, and eco-concern is increasing among the consumers,new technologies are emerging; natural fibers are being used, creatingnon-woven with attributes never seen before.

Silk non-woven

An attempthas been made to develop silk non-woven fabrics from silk reeling waste andhard waste generated during twisting and weaving on shuttle-less looms. In theprocess of conversion of cocoon to fabric, about 4000 MT of silk waste ofdifferent forms is being generated, annually. At present, this waste is usedfor manufacture of spun silk yarn, noil yarn, throwster yarn and carpet yarn,besides hand spun yarn. This waste can be more effectively utilized fordevelopment of silk non-woven fabrics for diversified end uses. Also, the hardwaste generated to the extent of 300 MT in silk twisting and weaving by 100%export oriented units (EOUs) is not being used for any value added purposeexcept in manufacture of coarser yarn for carpets. The same may effectively beutilized for development of non-woven silk fabrics.

Process and products

Preparation of thefibre: Thehard waste was sorted and separated from other non-silk materials and cottonleno threads. The lengthier yarns were cut into the size of 3 to 4 inches.

Processing(Stripping of colour, degumming and bleaching): The waste was thentreated with sodium hydrosulphite (Hydrose) at 70-800C and pH of 9.5-10, forremoval of dyes present in the waste. The waste was degummed with soap and sodafor removal of sericin. Further, the material was bleached with Hydrogen peroxide.

Openingand carding: The material, with and without decolouring and bleaching, wasprocessed separately in opening and carding machines. After carding, it was notpossible to take out the opened fibre in the web form from carding machine dueto smoother surface and absence of crimps in fibre. The web was converted intosliver form.

Webformation and needle punching: The needle punch process is illustrated inFig.1. Needle punched non-woven fabrics are created mechanically, orienting andinterlocking the fibers of a spun bonded or carded web. This mechanicalinterlocking is achieved with thousands of barbed felting needles repeatedlypassing into and out of the web.

The sliver collected from the carding machine were fed along with the polyester net fabric on one side, parallel to form sheet extending to full width (45 inch) in to the needle loom. The bonding of the sliver web was done by needle punching where thousands of oscillating needles penetrate the web in the vertical direction. The needles push and pull the fibres in vertical direction causing entanglement and create a stable web. The once punched web was fed again with another layer of slivers on opposite face and punched.

The needle punching was done in two stages in two needle looms with different needle board of coarser (1500 needle) and finer (10000 needle) at a speed of 600 rpm and thus, forming non-woven fabric ranging from 100 to 400 gsm. The polyester net fabric in a sandwich or reinforced fashion in between the layers of silk web, holds it together and supports the entanglement of fibres.

Dyeing, printing & finishing: The non-woven fabric was then dyed/printed and decatised (finishing) for different end uses. The finished fabrics are shown below.

Outcome

With this, a beginning has been made for the development of silk non-woven from silk reeling waste and hard silk waste generated during weaving on shuttle-less looms for value addition. The other wastes like pierced and cut cocoons are also being tried. The web formation by air laid method and bonding by chemical/needle punching is being attempted. Based on the end-uses, non-woven fabric of specific weight can be produced for various applications including technical and medical textiles. And, the possible end-use applications are rather unlimited and non-woven silk fabrics could be a potential input in the areas of inner lining for warm garments, head wears, ties, garments and blankets, carpets, furnishing and home apparels, automotive carpeting and insulation, wall coverings, handicrafts like wall paintings, wall hangings, wall coverings, gift tags, purse/wallets, table mats, matting for pictures, journal/book/album covers, greeting/invitation/business cards, lamp shades and many more. Perhaps, the imagination would be the limit.

Nonwoven Carpet

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