non woven

Non woven
Nonwoven fabrics are broadly defined as sheet or web structures made of fibers or filaments bonded or interlocked together by mechanical, thermal, chemical or solvent means. They are flat, porous sheets that are made directly from separate fibers or from molten plastic or plastic film. They are not made by weaving or knitting and do not require converting the fibers to yarn.

1. Non woven
Nonwoven fabrics are broadly defined as sheet or web structures made of fibers or filaments bonded or
interlocked together by mechanical, thermal, chemical or solvent means. They are flat, porous sheets that
are made directly from separate fibers or from molten plastic or plastic film. They are not made by
weaving or knitting and do not require converting the fibers to yarn.

In fiber processing it is common to make first a thin layer of fiber called a web and then to lay several
webs on top of each other to form a batt, which goes directly to bonding.

Properties of Non-woven Fabric:
Some important characteristics of non-woven fabrics have pointed out in the below:

1. The presence of non-woven fabrics may be felt like, paper like or very similar to that
of woven fabrics.
2. Non-woven fabric may be too much thicker or as thin as tissue paper.
3. It may be opaque or translucent.
4. Some non-woven fabrics have excellent launder ability where others have none.
5. The drapability of non-woven fabric varies from good to none at all.
6. Burst strength of this fabric is to very high tensile strength.
7. Non-woven fabric may be fabricated by gluing, sewing or heat bonding.
8. Non-woven fabric may have a resilient, soft hand.
9. This type of fabric may be stiff, hard, or broadly with little pliability.
10. Their porosity may range from low tear and burst strength to very high tensile strength.
11. Some non-woven fabrics may be dry-cleaned.

2. Classification of Non-woven fabrics
According to the properties:
1. Flame retardant
2. Water repellent
3. Water absorbent etc.
According to the use of raw materials
1. Durable
2. Semi-durable
3. Disposable
According to the use of raw materials
1. Staple fiber nonwoven
2. Filament fiber nonwoven

3. According to the method of production:
1. Wet bonded
2. Dry bonded
3. Spun bonded
The nonwoven fabrics can also be classified depending on fiber length such as:

A. Nonwoven of staple fiber
1. Dry laid nonwoven (parallel/ cross laid/ randomly laid)
2. Wet laid nonwoven
B. Continuous filament nonwoven
1. Spun laid nonwoven
2. Melt blown nonwoven

Process sequence for manufacturing nonwoven fabric


Wet-laid Nonwovens
The fibers are dispersed in water and then laid on a wire mesh to filter the liquid and form a web, which is
transferred to a drying felt before finally being heat cured in a continuous process. It produces a web in
which fibers are randomly oriented. These webs are then superimposed on one another in a parallel
fashion. The fiber is netted in the wet state and then consolidated into cloth, that’s why it is termed as
wet-laid nonwoven fabrics.

4. Characteristics of wet-laid nonwoven fabrics

1. High production speed, up to 400 m/min.
2. Short fibers can be fully utilized.
3. The uniformity of fiber mesh is good.
4. Large water consumption and high one-time investment.

Product development by wet-laid process
1. Special paper : Dust/liquid filter paper, tea bag.
2. Industrial : filters, insulation materials, sound-absorbing materials.
3. Medical use : medical backing, medical tape, surgical bag wrapping materials.
4. Civil : wallpaper, etc.

Dry laid nonwoven
Dry laid nonwovens are mainly produced using staple fiber either from natural or synthetic fibers. Dry
laid web formation mainly consists of 4 steps as below

5. Staple fiber preparation
Usually naturally fibers in staple form are directly used to produce nonwoven fabrics but manmade fibers
are needed to be cut into staple fibers to manufacture nonwoven fabrics.

Opening, cleaning, mixing and blending
In this stage machinery are used to make the fiber individual form, clean the impurities from fiber and
combine different types of fibers as per requirements. Following machinery can be used to fulfill the
requirements.
i. Bale opener or bale pluckers
ii. Cleaning machine (mono cylinder or dicylinder)
iii. Blending machine (Uni-mix, uni-blend, mix master) etc


Carding
This process follows the initial opening of the raw material. The tufts of the fiber fed into the machine and
then reduce them to an individual fiber state. The individualization of fibers allows the removal of the
much of the impurities. Finally the carding machine reduces the overall thickness of the material into the
form of light web.
Web laying
There are mainly three types of web laying techniques in case of dry-laid webs;
i. Parallel laid webs
ii. Cross laid webs
iii. Randomly laid webs or air laid webs
Spun bonded Nonwovens
In this process polymer granules are melted and molten polymer is extruded through spinnerets. After the
polymer has been extruded and stretched to form continuous filaments, the filaments are laid into nets,
which are then self-bonded, heat-bonded, chemically bonded or mechanically strengthened to turn the
nets into non-woven fabrics.

6. Characteristics

1. The nonwoven fabric consists of continuous filaments
2. Excellent tensile strength
3. There are many technological changes, which can be strengthened by various methods
4. The range of filament size change is wide.

Melt Blown Nonwovens
These are produced initially in the same manner as spun-laid webs. In this process, a thermoplastic fiber
forming polymer is extruded through a linear die containing several hundred small orifices. Convergent
streams of hot air rapidly attenuate the extruded polymer streams to form extremely fine diameter fibers
(1-5 micrometer). The attenuated fibers are subsequently blown by high-velocity air onto a collector
conveyor, thus forming a fine fibered self-bonded melt blown nonwoven fabric.

Characteristics
1. The web consists of very fine short fibers
2. Fiber mesh has good uniformity and soft handle
3. Good filtration and liquid absorption performance
4. The strength of the web is poor.


Bonding technology for producing nonwoven fabrics
Chemical bonding
It involves the application of adhesive binders by a range of processes including spraying, printing,
saturating and foaming.
Thermal bonding
It requires heat and pressure to fuse or weld fibers together at points of interaction or in patterned bond
sites. This usually involves including a fiber with a lower melting point in the web.
Solvent bonding
It achieves by softening or partially dissolving fibers with a solvent to provide self bonding surfaces.
Mechanical bonding
It includes needle punching, stitch bonding and hydro-entangling.

7. Mechanical bonding
In mechanical bonding the strengthening of the web is achieved by inter-fiber friction as a result of the
physical entanglement of the fibers. There are two major types of mechanical bonding:

1. Needle punching
2. Hydro-entanglement

Needle-punched non-woven fabric
Needle punching can be used on most fiber types. Specially designed needles are pushed and pulled
through the web to entangle the fibers. Fibers are entangled using barbed needles that penetrate the web
entangling the fibers. Webs of different characteristics can be needled together to produce a gradation of
properties difficult to achieve by other means.

web
punch
needle (barbs point downward for easy extraction)

8. Characteristics
1. Flexible entanglement between fibers has good dimensional stability and elasticity
2. Good permeability and filtration performance
3. Full and fluffy feel
4. Various sets of patterns or stereo-forming products can be manufactured according to
requirements.

Application of Non-woven Fabric
 Automotive
 Medical
 Personal care and hygiene
 Home furnishings
 Household
 Stationery
 Agriculture
 Geo-textiles
Applications of Nonwoven fabric in automotive
Floor covers, seats, interior trim, cabin air filters, airbags, wheel housing, dashboard insulation, hood
insulation, filtration, molded bonnet liners, heat shields, parcel shelf.
Medical Applications
Disposable caps, gowns, masks, scrub suits and shoe covers, drapes, wraps and packs, sponges, dressings
and wipes, bed linen, contamination control gowns, examination gowns, lab coats, isolation gowns,
transdermal drug delivery, shrouds, underpads, procedure packs, heat packs, ostomy bag liners, fixation
tapes, incubator mattress, sterilization wraps, wound care, cold/heat packs, drug delivery.

Personal and hygiene
Baby wipes, facial wipes, cleansing wipes, hand and body wipes, moist towelettes, personal hygiene
wipes, feminine hygiene wipes, antibacterial wipes, medicated wipes, baby diapers, feminine hygiene
products, and adult incontinence products.

Application in household purposes

Abrasives, bed linen, blinds/curtains, carpet/carpet backings, covering and separation material, detergent
pouches/fabric softener sheets, flooring, furniture/ upholstery, mops, table linen, tea and coffee bags,
vacuum cleaning bags, wall covering, wipes.

9. Leisure and travel
Sleeping bags, tarpaulins, tents, artificial leather, luggage, pillow cases.

Stationery
Book covers, mailing envelops, labels, promotional items, posters, banners etc.

Agriculture
Crop covers, turf protection products, nursery overwintering, root bags, capillary matting, green house
shading, seed blanket.
Geo-textiles
Roads and railroad beds, soil stabilization, drainage, artificial turf, sedimentation and erosion control,
Dam and stream embankments.