Knitted Fabrics For Industrial Application

The production of various types of industrial fabrics for industrial application is almost as old as the mechanical weaving operation itself, and these end uses are important today. Whatare new and extremely attractive to the manufacturer are the growth in industrial textiles and

its application in the sectors such as agriculture, construction, geotextiles, automotive,

protective apparel, electronics etc. This rapid increase in market potential has led these high

profile manufacturers to develop specialized fabric for knitting and serving the end purpose

efficiently. In this paper focused various knitted fabrics used for manufacturing of industrial

textiles have been reviewed.

1. INTRODUTION:

Knitting is one of several ways to turn thread or yarn into cloth (compare to weaving, crochet).

Unlike woven fabric, knitted fabric consists entirely of horizontal parallel courses of yarn. The

courses are joined to each other by interlocking loops in which a short loop of one course of

yarn is wrapped over the bight of another course. Knitting can be done either by hand,

described below, or by knitting machine. In practice, hand knitting is usually begun (or "cast

on") by forming a base series of twisted loops of yarn on a knitting needle. A second knitting

needle is then used to reach through each loop (or stitch) in succession in order to snag a

bight of yarn and pull a length back through the loop. This forms a new stitch. Work can

proceed in the round (circular knitting) or by going back and forth in rows. Knitting can also be

done by machines, which use a different mechanical system to produce nearly identical

results.

The knitting process consists of interconnecting loops of yarn on powered automated

machines. The machines are equipped with rows of small, hooked needles to draw formed

yarn loops through previously formed loops. The fabric is designed to take force in two

directions (0° and 90°). For this can be used roving of glass, high tenacity polyester, armid or

carbon as pillar threads and weft threads. These fabrics are used for reinforced composites.

Considering though orientation of the force taking yarns (0°, 90°) this fabric is comparable to a

woven fabric. However, there is the advantage that yarns are directly oriented and lie

absolutely straight in the fabric. This means that there is no loss of tenacity as in the woven

due to its crimp effect. Furthermore, the yarn-protective inlay system prevents all fiber

damage.

Warp knitted Woven fabric:

1.1. Innovation:

3D-Glass-textiles, manufactured on double needle bar high speed Raschel machines of LIBA

find ever more fields of application within the area of composite materials, technical textiles.

1.2. Manufacturing properties:

Made of 100% e-glass, one uses the capillary function of the glass, i.e. when absorbing the

resin, the commodity sets up itself automatically to the desired height.

1.3. Variety:

Whether as isolation layer in the boat- and container construction or as double-walled tanks,

these so-called spacer fabrics perform particularly well. Caused by the fabric construction,

after laminating, a more stable, lightweight and ductile composite develops.

1.4. Flexibility:

Depending on the final product, the thickness of the fabric can be adjusted between 3mm to

15mm directly at the machine. By using a special design technique, a thickness of even 25

mm can be achieved.

1.5. Applications:

Composite reinforcements (Sandwich-constructions)

Container

Tanks

Boats

Aircraft

Sport shoes

Medical textiles and Mattress

2. Geotextiles Application:

Geotextiles are permeable textile materials which are designed for use in civil engineering

applications such as erosion control, soil reinforcement, separation, filtration and drainage

etc. Geotextiles are forecast to be the fastest growing sector within the market for technical

textiles. At least 70% of all geotextile fabrics fall into the category of nonwoven geotextiles

and at least 25% are woven both warp knitted and weft knitted structures are used in the

manufacture of geotextiles.

Warp knitting is well established in this area and an extremely wide range of structures

spanning from nets and grids to monoaxial, biaxial, triaxial, multiaxial as well as composite

and three-dimensional spacer materials are all used as geotextiles. Grid shape structures

grip the soil more effectively than plain smooth fabrics. Also, for extremely high performance

and critical applications – such as land reclamation, construction of high walls and water

reservoir embankments – high strength (up to 1000 k N m-1) biaxial raschel structures are

more suitable. These fabrics have high strength, low extensibility, and high modulus, above

all, high tear strength.

A new and novel technology has been developed and commercialised at Bolton Institute,

which enables the manufacture of monoaxial and biaxial specialist natural fibre geotextile

structures for soil reinforcement. The technology is based on flat knitting, in which high

strength coarse and hairy natural fibre yarns such as sisal, coir etc can be inlaid in the

machine or cross, or both directions and incorporated within a knitted structure made from

jute, flax and other natural fibre yarns, such as cotton, viscose, Tencal, wool etc.

It is possible to manufacture designer natural fibre geotextile structures for specific short-term

solutions. These Directionally Structured Textile Fabrics have been patented, and are

currently being commercialised for mass production. Figures 1 and 2 illustrate the novel weft

knitted structures and Figures 3, 4 and 5 shows the modified mechanically operated flat

machine which enables either warp or weft or both threads to be incorporated within the fabric

structure.

2.1. Knitted Spacer Fabrics:

Warp and weft knitted spacer fabrics continue to find new and novel product applications and

it is generally recognized that spacer fabrics will be extensively used in the future in a wide

range of products, mainly due to the fact that an extremely wide range of possibilities are

available to tailor make their aesthetical, functional and technical properties for applications.

2.1.1. Warp Knitted Spacer Fabrics:

Warp knitted spacer fabrics are structures that consist of two separately-produced fabric

layers which are joined back to back. The two layers can be produced from different

materials and can have completely different structures. The yarns which join the two face

fabrics can either fix the layers directly or space them apart. It is this three-dimensional space

which is the special feature of these structures. Typically, spacer fabrics can be from 1 to 15

mm thick, with the two faces being from 0.4 to 1 mm thick. The major single feature of warp

knitted spacer fabrics is that virtually any thickness can be obtained, depending upon the type

of machinery used and the type of yarns and structures used. The warp knitted spacer fabric

with a thickness of over 100 mm (4 inches) for use as a seating fabric for sports cars.

Spacer structure manufactured in one process:

· Up to 15 mm spacer distance

· Up to 3, 3 m full fabric width

· Large pattern variety for outside cover fabric and

spacer structure

3. Karl Mayer spacer machine RD6N:

In which guide bars 1 and 2 knit the front base fabric on the front needle bar only and

guide bars 5 and 6 knit the other separate base fabric on the back needle bar only. Guide

bars 3 and 4, which carry the spacer threads knit on both needle bars in succession. The

thickness of the spacer depends upon the distance between the two needle bars and can be

varied between 1 and 15 mm. In theory the material used in guide bars 1 and 2; 3 and 4; and

5 and 6 can be different, as well as the structure of the two base fabrics can be completely

different. It is possible to vary the structure from an inelastic, elastic, solid, net or a specific

textured surface independently in each face fabric. Furthermore, the compression and

resilience properties of the spacer can be altered at will, depending upon the material and the

pattern chains of the threads in guide bars 3 and 4.

The major benefit of using spacer material is to replace polyurethane, neoprene and other

types of foams which are laminated to textile fabrics for creating bulk, softness, flexibility,

resilience etc. These foams, however, have some serious drawbacks. For instance, foams

are generally flammable; they are extremely uncomfortable due to extremely small cavities.

Their thermo physiological properties are poor, their compression and resilience properties

deteriorate with time and their mouldability, delamination, maintenance of original thickness

when moulded into complex three-dimensional shapes, washing and drying properties are

often poor and not up to the standard required. Relatively stiff monofilaments generally used

as spacer material, more or less overcome the above-mentioned drawbacks associated with

laminated structures

The major product applications for warp knitted spacer materials are: car seat covers (both

solid or net structures in the face or back or both surfaces); automotive interiors (lining for

doors, roofs, convertible hoods etc); seat heating systems for cars; mud flaps for lorries and

buses; insoles and face fabric for sports and other shoes; lining for rubber and other boots;

protective inner lining; mattress underlays and mattress covers for prevention and

management of incontinence, pressure sores as well as for children’s beds; diving and surfing

suits; sports equipment; high-performance sportswear; reinforcement for composite

structures; bras; underwear; swimwear; shoulder pads; fluid filters; geotextiles; bandages;

plaster casts; braces; controlled release of drugs, antimicrobials, cosmetics etc; and finally

heat and moisture regulation fabrics.

3.1. SPACER FABRIC KNITTING:

Machine details:

High speed knitting process

• 6 Guide bars

• Gauge E6 – E14

• Working width 84” (213 mm) and 130” (330

mm)

• New linear system for easy variation of

spacer fabric thickness

• Easy access to knitting elements

3.1.1. Weft Knitted Spacer Fabrics:

Weft knitted spacer fabrics can be produced on circular double jersey machines as well as

electronically controlled flat machines. The major advantages of these structures are:

a) plain as well as colour and design and surface texture effects can be produced on the

face of the fabric knitted by the cylinder needles; and

b) Shaped and true three-dimensional structures can be produced on electronically

controlled flat machines.

The major limitations of weft knitted spacer fabrics are:

a) The thickness of the spacer is normally limited to between 2 and 10 mm

b) The basic structure of the spacer fabric is limited to either knitting the spacer threads

on the dial and tucking on the cylinder, or tucking the spacer threads on the dial and

cylinder needles.

It is obviously more practical to use tuck stitches with spacer monofilament yarns in order to

ensure that the spacer yarns lie correctly inside the knitted fabric and prevent the face and

back of the fabric from having a rough or harsh feel.

Knitting Constructions:

The structure of a circular knitted monofilament spacer fabric is Produced on circular interlock

gaited machines are shown in Figures. Three different yarns are required for each course:

a) Yarn for the dial needles

b) Yarn for the cylinder needles

c) Spacer yarn, normally monofilament yarn.

CONCLUSION:

The future scope of fabric science is very broad. Only innovative products will be able to open

up new markets and new horizons for the textile industry. To achieve this, it is essential to

invest in future research and researches. In the coming years, knitted fabrics will increasingly

take on industrial functions. Fabric will combine the functions of medium, carrier and interface

for an extremely wide range of industrial applications. This new generation of industrial fabric

makes considerable new demands on the innovative ability within the clothing industry. What

is needed is not simply the conveyance of knowledge but the development of truly creative

researchers. The textile industry needs to shift its emphasis from ‘quantity, quality; to

‘functionality’ in the new millennium of Global Competition Era.

REFERENCE:

1. S. C. Anand, Developments in Technical Fabrics – Part 1, Knitting International, July

2000, page 32

2. M. Hard castle, In the Driving Seat, Knitting International, July 2001, page 52

3. 7. T. Shah and S. C. Anand, Geotextiles: A Growing Market for Technical

Textiles, Technical Textiles Markets, 2nd Quarter 2002, page 34

4. S. C. Anand, Developments in Technical Fabrics – Part 2, Knitting

International, August 2000, page 53

5. S. C. Anand et. al., Directionally Structured Textile Fabrics, UK patent

Number GB2339803, published on 27th November 2002

6. Double-Layer, Circular Weft Knitted Fabrics with Monofilaments (Spacer

Fabrics), Knitting Technique, 16, 5, 1994, page 306

7. J. Millington, Do We Have Lift Off, Knitting International, October 2002,