non woven products and production

7/30/2019 Non Woven Products and Production

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Nonwoven FabricsA brief description of nonwoven fabrics usedas Technical TextilesDr Muhammad Mushtaq Mangat

www.mushtaqmangat.orgDec 24, 2012


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Nonwoven fabricsA nonwoven is a textile structure producedby the bonding or interlocking of fibres, orboth, accomplished by mechanical,

chemical, thermal or solvent means andcombinations thereof (ASTM D 1117-80).[1]


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Nonwoven fabrics are broadly defined assheet or web structures bonded together byentangling fibre or filaments (and by

perforating films) mechanically, thermally or chemically. They are flat, porous sheetsmade directly from separate fibres or frommolten plastic or plastic film. They are notmade by weaving or knitting and do notrequire converting the fibres to yarn.

[4]


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ContiA nonwoven is a sheet of fibres, continuousfilaments, or chopped yarns of any nature or origin, that have been formed into a web by

any means, and bonded together by anymeans, with the exception of weaving or knitting. [4]


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[2]


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[3]


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Hygiene

[http://en.wikipedia.org/wiki/Nonwoven_Fabric]

baby diapers or nappiesfeminine hygiene

adult incontinence productswet wipes

bandages and wound dressings

disposable bath and face towels

disposable slippers and footwear


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Medical

isolation gowns

surgical gowns

surgical drapes and covers

surgical scrub suits

caps

medical packaging: porosity allows gassterilization


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Filters

gasoline, oil and air - including HEPA filtration

water, coffee, tea bags

pharmaceutical industry

mineral processing

liquid cartridge and bag filters

vacuum bagsallergen membranes or laminates with nonwoven layers


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Geotextilessoil stabilizers and roadway underlayment

foundation stabilizers, erosion control, canalsconstruction

drainage systems, geomembrane protection

frost protection, agriculture mulch, pond andcanal water barriers, sand infiltration barrier for drainage tile, landfill liners


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Other

carpet backing, primary and secondary, compositeschopped strand material, backing/stabilizer for machine embroidery

packaging where porosity is needed, insulation

(fiberglass batting), pillows, cushions, and upholsterypadding, batting in quilts or comforters

consumer and medical face masks, mailingenvelopes

tarps, tenting and transportation (lumber, steel)wrapping, disposable clothing (foot coverings,coveralls), weather resistant house wrap


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Advantages of Nonwoven

A continuous process, straight from fiber tofinish product

Low labor cost

Mass-production approach

Suitable for insulation containing only 23%fibers by volume

For stiff reinforcing, fiber content may beover 80% by volume


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Nonwoven Production

MethodsLaying of fibers and BondingDirect membrane (electro spinning)

Difference of batt and webBatt is first layers and web is the wholematerial [1]


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Nonwoven ProductionIn three stages

Web FormationWeb BondingFinishing Treatments


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Methods of batt production using

carding machines

Two main stepsWeb manufacturingBonding of fibers; thermal, mechanical,

chemical bonding etc.


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Parallel laying methods

[1][1]


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Batt and WebWeb planner weight is normally low (thin web)

Multiple webs increase planner weight anduniformity

Parallel laying is easiest and cheapest way

Mostly fibers are along the x-axis

Whatever method of bonding

Web strength depends upon the strength offibers not on the binding


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Laying processesDry, most popular:

parallel-laidcross-laid

Wet


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Parallel and Cross-

sectionalSpecial cards to make fibers more random,which have short length

It increases the strength

Gives buckling effect

Card modification can avoid layingunnecessary

Increase in thickness decreases the width offabric


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Cross layingCards are placed at right angles to the mainconveyor

card web is traversed backwards andforwards across the main conveyor, whichitself is moving. The result is a zig-zag [1]


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[1]


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Characteristics of CrossWeb

Short width

Zig-zag marks

Edges are thicker than middle

Mismatch between card and input layer speed

Cross-laying angle is normally less than 10

Majority of fibres lie in or near the cross directionCross-laid fabrics are very strong in the crossdirection and weak in the machine direction [1]


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Air laying

Direct final layer than making first layer

Production is high

Wider width web is possible 34 mUnopened lumps of fibers are vey common[1]


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[1]


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Air Laying Characteristics

Fabric made by air laying is more stronger

More random arrangement of fibers, it is alsocalled random-laid fabrics


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Wet LayingDeveloped by paper industry

Textile fibers and wood pulp is mixed

More than 50% fiber makes it non-wovenFibers are used to control the cost

Mostly disposable items are made by using

this technique


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non-woven wet tissues


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[http://www.engr.utk.edu/mse/Textiles/Wet%20Laid%20Nonwovens.htm]


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Spun laying

Direct laying from extrusion

Shortest way

More versatile

Small size machines have been developed

Much useful for microfibers, ultimately fine filters arepossible

Membrane are possible with nano fibers

Extra light weight fabrics are possible

Becoming popular due to short and versatile process


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[1]


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Spun Laying IssuesUneven batt

Coagulation and agglomerations of fibersgive un-even surface

Variation in pores is possible

Pore sizes and directions play a significantrole in strength and filtration process


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Nano fibersmats


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Flash SpinningA process to produce fine fibers without the application of finespinneret holes

It depends upon intramolecular bonds of polymers

Mainly polyethylene and polypropylene are used as substance

to produce fabricIntramolecular strength of PE and PP is weaker as compared toPET

Bending, twisting or abrasion is quite difficult for PE and PPfabrics

fibrillation.

In flash spinning the polymer is dissolved in


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Flash SpinningPolymer is dissolved in a solvent

Extruded as a sheet

Blow is used to make polymer sheet

Mass bubbles have large surface area

Low wall thickness

Fibrillation is carried out, which makes a network of fibers of very fine sheet

Desired GSM is obtain


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Flash Spinning ProductsFlash-spun material is only bonded in two ways:

melting the fibers under high pressure to makestrong adhesion of fibers, negligible air permeability, stiff sheets are produced

Partially pressure and heat, it make strong sheetsbut flexible called Tyvek. It is used for protectiveclothing in the

chemical, nuclear and oil industries, probably asprotection for the armed forces and garments


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Melt blown

Polymer is melted and passed throughextruders of large area

Hot air is put on polymer streams, whichconverts it into fine fibers

Cold air is brought in contact, which solidifythe fibers

Fine fibers are collected on a perforatedconveyor


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[1]


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Flash Spinning ProductsUltrafine filters for air conditioning

Personal face masks

Oil-spill absorbentsPersonal hygiene products


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Flash Sinning Products


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Chemical Bonding

Batt and webs are bonded with adhesivespartially or fully

Normally synthetic lattices are used

Curing is done at higher temperature for proper binding

Chemical bonding process


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Chemical bonding process


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Saturation bonding

Whole batt is wetted with adhesive

It is carried out undersurface of the bonding agent

In this case batt has wide pores, need care to avoiddistortion

Thin batt is produced due to pressure duringsqueezing

Such fabrics are compact

Fibers are crushed and spin back Drying is done on dryers having perforated conveyor


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ContFabric is quite compact, all fibers are covered

Sheet is possible

Strong enough to withstand under higher stretching

One of the major uses of saturation bondedfabric turns this apparent disadvantage

Such fabric is used as interlining fabric for textileclothing and as filter fabrics


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Foam bonding

Foam reduces the demand of water

Air is used to make foam and then bat isimpregnated


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Foam Impregnating

[1]


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Print Bonding

It is printing of designs with adhesive on batt

Batt is wetted then printed with any bindingagents

Print-bonded fabrics are quite flexible and soft

Fabric is weaker as compared to other fabrics

Such fabrics are used as disposable/protectiveclothing, cover stock and wiping cloths, dustingmaterial


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Print Bonded Fabric


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Spray bonding

Latex binders are sprayed instead of printing withthe help of compressed air

It could be spray after laying another batt, or onboth sides of batt

It reduces the thickness

Finally drying and curing is done

Fnal product is a thick, open and lofty fabric

Used as filling in quilted fabrics, for bedding for some upholstery and also for some types of filters[1]


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Thermal bondingBecoming popular due to easy and high production

No drying and curing is required

Less energy is demanded

Suitable for:Same types of fibers fibers can be bonded together by using partial binding or fully bonding due makingit a sheetBlend of fibers, some fibers bonded together but fewremains free, it make fabric soft and flexibleSpecial fibers having different polymer in surroundingand in the core. External fibers are melted and inner remained intact


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Thermal bonding without

pressureIn this case batt is processed withoutpressure,

Fibers are kept open and thick and highly

porous products are possible

Uniform bonding, more liberty in thicknessand porosity

Formula 1 cars fuel tanks are made by usingsuch fabric


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Thermal bonding with some

pressureSame as previous but the difference ispressure

Product is used filters and packing

More stiff and can have precise thickness

Thermal bonding is used also in book bindings, lamination with the help of thermal


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Thermal bonding with point contact

Similar to printing or spraying

Not whole batt is bonded

Some selected area is bonded

Fabric becomes flexible and soft feel

Less strong than whole bonded

Engraved calenders rolls are used for pointed binding

It may be less than 5% of the whole areaUsed as geo textile, filters, tufted carpets , homeproducts, covers


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Powder bonding

Thermoplastic powders can be added toany batt to produce thermal bonding incertain areas

Flexible fabric and having higher porosity

Low strength

Used as covers


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Solvent bonding

Not much popular

Needs more care to handle solvents

Solvent can be recycled

Less energy is required

More eco friendly

Solvent gas can be used

Latent solvent are used, which becomes solvents at higher temperature

Batt is impregnated in solvent then passed through a chamber at higher temperature, cooling is done to recover the solvent

Special fabrics are produced by using this technique


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Mechanical Bonding

Needle felting

Hydro entanglement

Fiber entanglements due to friction


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Needle FeltingBatt is put between two stationary plates

Batt is penetrated by a large number ofneedles

Needles have cuts to create moreentanglement

Needles are long enough to create a

uniform entanglement

Needle


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Needlepunching [1]


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Needle FeltingNeedle creates vertical loops, which are not sufficient

Much align fabric is not suitable

Need batt having vertical arrangement of fibers for

horizontal loops, which are required for high strengthArrangement between needle movement andconveyor movement determines the amount ofentanglement

Number of needles per unit area of plate plays acrucial role in strength of fabric


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ContiThere are two ways to increase production:

Increase of number of needlesIncrease speed of conveyor

There are more than 5000 types of needles available

Needle felt has high breaking tenacity and high tear strength

Poor extensibility

Some binding chemicals are used for better stability

Major advantage is that whole fabric ishomogeneous ,


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ContNeedle felt fabric is used:

gas filtration, wet filtration


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Needle punching line

Stit h b di


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Stitch bonding

Idea developed in Czechoslovakia

Lot of variation in process is possible like:Batt bonded by threads

Stitch bonding without threadsStitch bonding to produce a pile fabricBatt looped through a supporting structureLaid yarns sewn together with binding

threads


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Hydro entanglement

Hydro entanglement is a process similar toneedle loom

Invented by by Du Pont in 1960sMuch need is required to avoid turbulence

Jet are at 90 angle to the perforated conveyor,extra water is collected

Fibers become twisted together or entangled bythe turbulence in the water


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Conti

Common use of such fabrics:

wipes, surgeons gowns, disposableprotective clothing and backing fabrics for

coating

Wipes produced are guaranteed lint free,loose fibers are washed away

Light and heavy weight fabrics can beprocessed

R f


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References

[1] Smith, P.A., Technical fabric structures,Nonwoven fabrics , in Handbook of TechnicalTextiles A.R. Horrocks, Anand, S. C., Editor 2000, Woodhead Publishing Ltd Cambridge.

[2] Source: CSIRO Textiles & Fibre Technology

[3] The Australian Technical Textiles &Nonwovens Industry Profile May 2006

[4] http://nonwovenbagmachines.com/non-wovensectors.html


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