Non Woven

NONWOVEN

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A nonwoven is a sheet of fibres, continuous

filaments, of any nature or origin, that have

been formed into a web and bonded together

by mechanical, chemical or thermal means

NONWOVEN

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Nonwovens have specific characteristics that allow them to deliver high-

performance across a wide range of applications. Specific functions include:

- absorbency, - liquid repellency,

- resilience, - stretch,

- softness, - strength,

- flame retardancy, - washability (selective products),

- cushioning, - filtering,

- bacterial barrier and sterility

The versatility of nonwovens means that they can provide innovative,

cost-effective and sometimes unexpected answers to innumerable

business challenges.

NONWOVEN

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Specific properties can be achieved by selecting raw materials and methods or by

applying finishing treatments to nonwovens, such as printing, embossing, molding,

coating & laminating etc.

METHODOLOGY

The development of STANDARDS is on going and long term process.

The process will begin and proceed further with following steps:

• Identification of areas / properties to be standardizes:

– The important feed back is from industries which are facing problems

during day to day activity of manufacturing and trading nationally and

internationally. This will directly help to concentrate particular area.

– Comparing International Standards available, for evaluation of nonwoven

fabric and products, of various organisation including INDA and EDANA

with BIS will give detailed idea about absenteeism of standards available.

– Feed back from TRAs, COEs and the organizations involved in research will

give clear concept about requirement of standards for near future.

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PROPERTIES IDENTIFIED

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 Absorption  Repellency      Nonwoven Absorption - Absorbency, Absorptive Capacity, Wicking Rate

      Water Resistance: Impact Penetration Test 

      Nonwoven Absorption - Centrifuge Retention Capacity

      Water Resistance: Hydrostatic Pressure Test

      Nonwoven Absorption - Absorption Under Pressure  Surfaces and Biological

 Abrasion Resistance       Colonies      Abrasion Resistance of Textile Fabrics - Taber Abrasion

      BEE (Bacterial Entrapment Efficiency)

      Abrasion Resistance of Textile Fabrics - Martindale Abrasion (View test)

 Stiffness

 Bursting Strength       Cantilever      Diaphragm Method (Mullen)  Tear Strength      Ball Burst (Constant-Rate-of-Traverse)       Elmendorf      Ball Burst (Constant-Rate-of-Extension)       Trapezoid Chemical Analysis       Tongue      Component Analysis  Tensile Strength      Moisture       Grab      Ash       Seam Strength Image Analysis       Strip       Fiber diameter distribution  Thickness       Porosity, apertures and hole analysis        Nonwovens       Formation Analysis  Weight Permeability       Per Unit Area (Basis Weight)      Air Permeability  Coefficient of Friction      Water Vapor Transmission       Static and Kinetic      Nonwoven Coverstock Liquid Strike-Through – Rate; Simulated Urine

AREAS TARGETED

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• Development of Standards for Nonwoven

Fabric

• Development of Standards for Nonwoven

Products

• Products Specifications

DRAFT FORMULATION

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• A committee comprising of 15 members with five experts from each of the following categories

– Academicians, TRAs and COEs– Nonwovens fabric manufacturing Industry and– User / Converting industry

• Based on laboratory experimentations, test results, statistical evaluations, data collected; initial draft will be formulated and opened to industry, users and research organisation for feed back

• The nonwoven is basic technology used as intermediate product for various applications. Therefore, we expect the involvement of other COEs to achieve the targets.

• In due course of time with involvement and consultation / recommendation of BIS representative draft will be finalized for publication.

Non-woven

• Introduction• Web formation methods• Bonding Systems• Discussion

Introduction

• Fabrics can be made from fibres as well as from yarns.

• Conventional fabric production:– Fibre Yarn Fabric (knitting or weaving)

• Non-woven production– Fibre Fabric

• It eliminates the yarn production process and makes the fabric directly from fibres.

Introduction (2)

• The great advantages in non-woven fabrics is the speed with which the final fabric is produced.

• All yarn preparation steps are eliminated, and the fabric production itself is faster than conventional methods.

• To produce 500,000 meters of woven sheeting requires 2 months of yarn preparation, 3 months of weaving on 50 looms and 1 month for finishing and inspection.

• Non-woven fabric can deliver the same quantity of sheeting within 2 months from order.

Introduction (3)

• Not only are production rate are higher for nonwovens, but the process is more automated, requiring less labour than even most modern knitting or weaving systems.

• The nonwoven process is also efficient in its use of energy.

Production Rate

Fabric production method

Rate of fabric production

Weaving 1 m/min

Knitting 2 m/min

Nonwoven 100 m/min

Applications• Nonwoven fabrics can be engineered to give a wide

variety of properties.• Nevertheless, their aesthetic properties (handle,

drape, appearance) are such that they are not in direct competition with conventional fabrics in the outerwear market.

• Woven and knitted fabrics will not be replaced by nonwovens in the near futrue.

• Currently, the main areas of growth in nonwovens are in geotextiles, medical and hospital uses, disposable products and filters.

Making Non-woven products• There are normally two steps for making

non-woven products.• They are:

1. Web formation; and2. Bonding systems.

Web formation

• A nonwoven fabric is basically a web of fibres held together in some way.

• The web may be made of staple fibres or filaments, or from portions of polymer film.

Web formation from Staple Fibres

Web from staple fibres Carding for parallel-laid web (1)

• Carding is a time-honoured way of making web from staple fibres.

• In a carded web the fibres are aligned more or less parallel to each other and to the direction in which the card produces the web. Such web is stronger when pulled lengthwise than crosswise because there is more friction between the fibre in lengthwise direction.

• Carded webs are usually thin, they may be too thin for some nonwoven end-uses. To increase the final thickness, a number of webs can be layered.

PhotosParallel-laid web from carded fibres

Webs from staple fibresCross-laid web (2)

• To increase the strength of web in both lengthwise and crosswise directions, cross laid web is used.

• To achieve this, the fibres which make up the web will be orientated equally in both lengthwise and crosswise directions.

PhotosCross Laid-web

The properties of cross-laid webs do not vary with direction as much as do those of straight-laid web

Web from staple fibresRandom web (3)

• The Rando-Webber creates such a randomly orientated web by blowing the fibres about in a stream of air and then sucking them onto the surface of a perforated drum to form a layer.

• This randomizing process produces a remarkably uniform web from staple fibres.

• Dry-laid (air-laid card) webs account for three-quarters of non-woven produced

PhotosRandom Webs

The Rando-Webber gives a randomly orientated web, with noDirectionality in its properties

Other Web formation methods

• Apart from carding methods (dry-laid), webs from short staple fibres are created by

1. Wet laying;2. Electrostatic web formation; and3. Spraying.

Wet-layingPaper-making from web

• Wet laying is used in paper-making. The pulped fibres are mixed with water and then scooped into uniform layers on wire screens or on rotating, perforated drums.

• Short, pulped acrylic fibres are made into a wet-laid web from a salt solution. As the water evaporates, the salt chemically bonds the fibres into a strong, synthetic, water proof paper.

Web formed byelectrostatic laying

• In electrostatic laying, fine fibres are given a static electric charge between the plates of a condenser, and are then allowed to fall on a moving belt to form a randomly orientated but uniform web.

Spraying method

• Short thermoplastic fibres can be SPRAYED onto a belt to produce a random web.

• The are subsequently fused by the application of heat and pressure.

Webs from filament

Webs from filament• It is possible to tangle filaments together to form a web.

Such webs are much stronger than web made from staple fibres.

• Freshly extruded filaments are allowed to drop in curls and spiral onto a moving belt.

• The belt may contain patterns outlined in pins to form lace-like patterns.

• The thermoplastic filaments are welded to each other to form a strong fabric suitable for curtains, tablecloths.

• Sometimes, the filaments are textured before web formation, this allows greater extensibility of the fabric in use.

New web formation method• Spun-laced webs is a new method of entangling fibres to

create lace-like nonwoven fabrics uses fine, precisely controlled, jets of water.

• When the jets pass through the web of fibres, they form a small vortex at each point of contact.

• This creates sufficient fibre movement to entangle the fibres.

• The resultant fabric does not need any further reinforcing by heat or adhesive.

• It is pliable, resistant to damage during washing, drip-dry, light, warm and soft, excellent for curtains, table cloths and other lace-type application.

Non-woven

• Bonding systems in non-woven– Needled felts– Adhesives– Heat bonding– Stitch bonding

• Discussion

Introduction

• In last section, we introduced what is non-woven fabrics, its advantages and application.

• Non-woven production– Fibre Fabric

• To make non-woven fabric, the first step is web formation, to make a strong and parallel web.

• The second step called “bonding” is to combine different webs together to make a stronger layers (with different thickness and fabric weight) for particular end uses.

Bonding System1) Needled felts

• Fibres which have no directional frictional properties need to be mechanically entangled in order to form felts.

• This is done using barbed needles.• The products of needle felting are used for

carpets, underfelts, upholstery, and blankets.

Photos for needle punching (bonding)

Needle punching. The barbed needle tangles together some fibres from each layer of the web to make a stronger web.

Photos for needle punching (bonding)

Cross section of a needle-punched bonded fabric.

Bonding System2) Adhesives

• For most nonwoven applications, fibre-to-fibre friction does not provide enough strength.

• Adhesive can be effective in holding the fibres together.

• It is, however, important not to use too much adhesive or the natural properties of the fibres may be masked, giving the fabric properties of the adhesive rather than of the fibres.

PhotoAdhesive

Adhesive bonding on non-woven

Bodning2) Adhesive

• The adhesive can be applied to the web as a printed pattern or as a sprinkling of powder.

• The properties of an adhesive-bonded nonwoven depend to quite a large extent on the properties of the adhesive polymer used.

• Commonly used adhesives are polyvinyl acetate (PVA glue) polyacrylonitrile, PVC.

PhotosAdhesive Bonding

Adhesive bonding: a cellulosic wiper, with the adhesive applied in colour stripes and resin-impregnated fibreglass used to reinforce pipes

Heat Bonding• When a web of thermoplastic fibres (polyester, nylon) or

filament is heated, the fibres cross over each other at many points, there are many rigid welding spots in nonwoven fabric.

• This makes heat-bonded fabrics rather stiff and inextensible.• In order to produce a softer fabric without the use of adhesives,

thermoplastics fibres with lower melting point are blended in the web with fibers with higher melting point.

• On heating, only the low melting point fibers melt. • This way, fewer weld points are formed and the resultant fabric

has more desirable textile properties.• Such melt-welded fabrics are called Melded fabrics.

PhotoHeat bonding

Melt-bonding at selected points to give extra stability to a spun bonded polypropylene geotextile

Stitch Bonding• Webs may also be given extra strength by stitching them

through with yarns. • Such structures are usually more flexible and less paper-like

than heat-bonded or adhesive bonded nonwovens.• Stitch bonding is based on principle of warp knitting but with

needles designed to stitch through webs of various thickness.• A web of fibres or web of yarns or a cheap fabric forms the

base.• Sharp-pointed needles pierce the base and loop binding yarns

through it.• In this way, relatively cheap but stable fibres, with or without

pile, can be produced.

PhotoStitch bonding

Carpet underfelts are often stitch-bonded, and may incorporat a layer of loosely woven hessian for extra length