Prof. Shakeel Iqbal
Knitted Fabrics:–
Application and Scope
Haqiqat Ali (11)
1. INTRODUCTION
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.
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.
Fig. 2 Knitting
Fig. 1 Knitted and Woven fabric
2. KNITTING – MANUAL TO MACHINES
The oldest artifact with a knitted
appearance is a type of sock. It is believed
that socks and stockings were the first
pieces produced using techniques similar
to knitting. These socks were worked in a
technique of making fabric by creating
multiple knots or loops with a single
needle and thread. Several pieces, done in
now obscure techniques, have been
mistaken for knitting or crocheting.
The earliest known knitted items in
Europe were made by Muslim knitters employed by Spanish Christian royal
families. Several paintings from Europe portray the Virgin Mary knitting
and date from the 14th century. At this time, the purl stitch (the opposite
action to the knit stitch) was unknown and purely stockinet fabric was
produced by knitting in the round on multiple knitting needles. Sometimes
the knitting was cut open, a process now known as steeking. Knitting was
such a vast occupation among those living
on the Scottish Isles during the 17th and
18th centuries that whole families were
involved in making sweaters, accessories,
socks, stockings, etc.
With the advent of the Industrial
Revolution, wool spinning and cloth
manufacture increasingly shifted to
factories. Women were employed to
operate the machinery, rather than
spinning and knitting items at home. The
consistency of factory spun wool was
better in that it was more uniform, and its weight could be gauged better as
a consequence.
The city of Nottingham, particularly the district known as Lace Market,
dominated the production of machine-knitted lace during the Industrial
Revolution and the following decades.
Fig. 3 one of the oldest socks
pair
Fig. 4 knitted machine at
industrial revolution period
The 21st century has seen a resurgence of
knitting. Natural fibers from animals, such
as alpaca, angora, and merino, and plant
fibers, chiefly cotton, have become easier and
less costly to collect and process, and
therefore more widely available. Exotic fibers,
such as silk, bamboo, and qiviut, are growing
in popularity as well. The yarn industry has
started to make novelty yarns which produce
stunning results without years of knitting
experience. Designers have begun to create
patterns which work up quickly on large
needles, a phenomenon known as instant-
gratification knitting.
As time and technology change, so does the art of knitting. The Internet
allows knitters to connect, share interests and learn from each other,
whether across the street or across the globe. Among the first Internet
knitting phenomena was the popular Knit List with thousands of members.
In 1998, the first online knitting magazine, “KnitNet”, began publishing.
Blogging later added fuel the development of an international knitting
community.
Fig. 5 An advanced
knitting machine
Fig. 6, 7 complex knit patterns achieved with the help advancement in
technology
3. APPLICATION AND USES
Knit fabrics are versatile and are used to create not only clothing, but
certain home furnishings as well. Made from interlocking stitches, knits are
available in five different categories: firm, stable double knits that don't
have a lot of stretch; single knits, which are lightweight; textured knits, such
as velour or terry cloth; two-way stretch knits, which have a lot of stretch in
them; and ribbing, which is for finishing garments, like the necklines of T-
shirts.
3.1. Technical and Medical Textiles
Knitted fabrics and knitting technology play very
important role on the fields of technical and
medical textiles and their importance is ever
greater. Experts estimate that their annual
consumption is increasing by 3.8% in average
and it can reach about 24 million tons in 2010.
Within this the consumption of each sector is
increasing. Roughly one third of the world's fiber
consumption is used for production of technical
textiles.
Most of technical textiles are made of non-conventional materials; they are
usually man-made fibers, in many cases special types developed for specific
applications. Metallic yarns (thin wires) alone or parallel to other yarns are
also used in some technical knitted fabrics. However, traditional materials,
including those of natural origin, play important role in some fields.
There are various technical textiles which are manufactured by taking the
use of knitting technology. Some of them are discussed below:-
3.1.1 Nets
Application field of nets is extremely wide.
Agriculture, fishing, packaging, transport,
sports, shading technology, construction,
healthcare, surgery, safety technology and
military present many good examples for that.
Many of these nets are made by paschal or
crocheting technology the great advantage of
Fig. 7 knitted textile
supporting the joints
Fig. 8 a knitted net
which is that they do not contain knots. This makes the nets easier to handle
because the layers do not tangle up and there are no knots that could harm
the good packed into the net.
Materials used for net manufacture are very different, depending on the end
use. Spun yarns or filament yarns, narrow plastic tapes are commonly used
for this purpose. Elastic nets are made with using of elastane yarns.
3.1.2 Spacer fabrics
Among knitted fabrics perhaps the most
spectacular development can be registered in case
of spacer fabrics. Though the principle of the
fabrication is not new, it goes back to the
manufacture of plush fabrics on raschel machine;
the adaptation of this technology to make a
completely new type of fabric is very ingenious.
At the beginning they were developed really on
two needle bar raschel machines but now there are
also circular knitting machines on the market for
manufacturing of such products and, of course, V-
bed flat knitting machines are also able to make spacer fabrics of some
kinds.
The two surface layers of spacer fabrics are usually linked by relatively
thick monofilaments which make the fabric elastic when pressed in
thickness direction. This is the most important reason why spacer fabrics
have found many fields of application. They can substitute foam in seats or
beds, in orthopedics support devices, in bras and shoes. It can serve in smart
clothes as heat insulation or for forming of ventilation passages. As a type
of geotextiles spacer fabrics can be used to
lead off water from the soil. In
manufacturing of composites used in the
motor industry or ship building they can
work as reinforcement inlay. Using proper
yarns or with application of special
treatment they can be electrically
conductive, flame retardant, antibacterial,
etc.
Fig. 9 spacer fabric
Fig. 10 spacer fabric –
sandwich technology
As we see at this moment, most spacer fabrics used are made on raschel
machines or, in recent times, also on crochet machines. Needle bed distance
on these machines can be varied within wide range and fabric thickness can
reach even 60 mm. On circular knitting machines needle bed distance is
much more limited, only thinner (thickness of some millimeters) spacer
fabrics can be made on them. However, these variants are also very
important and can be found in many products.
3.1.3 Stitch bonded fabric
These fabrics have great importance in almost
each class of technical textiles. They are used
very often as reinforcing materials in
composites or for heat or sound insulation,
filling materials in clothes or furniture, etc.
Stitch bonding machines combine knitting and
sewing. They have grown from warp knitting
technology and their products occupy an
intermediate position between knitted and
nonwoven fabrics. This fabric contains a
carded web which is reinforced by yarns or
loops formed from fibers pulled out from the web itself. A further variant of
such fabrics is when not only carded web but lots of yarns are laid in
various directions over the web and all of these are stitched together. This
formation may be called “composite fabric” since it is a composition of
various types of textiles (web and yarns). They find application fields
among filters, geotextiles, reinforcement materials in composites, etc.
Advantage of these fabrics is that the carded web may be made of various
fibres which, because of their length or quality, cannot be spun, even in
various blending, fabric thickness and stitch density (number of stitches in
length unit) as well as yarn counts (in accordance with machine cut) can be
varied in relatively wide range. The fabric can be easily formed. At the end
of its lifetime it can be torn and recycled.
Fig. 11 stitch bonded fabric (Maliwatt)
3.1.4 Knitted fabrics with orientated behaviors
Knitted fabrics with orientated behaviors
are made usually with lots of yarns laid
lengthwise, crosswise and/or diagonally
into the fabric. Their keeping together is
performed by warp knitted loops. Aim of
these structures is mainly to reduce the stretch and/or to increase the fourth
of the fabric in one or more directions. If this effect is realized only in one
direction (lengthwise or crosswise) the fabric is called unidirectional or
monoaxial. If this behavior asserts itself in both directions the fabric is
called biaxial. Multiracial or multidirectional fabrics have almost the same
behavior in every direction.
To manufacture such fabrics special tricot and raschel machines have
been developed completed by equipment to prepare and lead the lots of
reinforcing yarns into the place of loop formation. In these fabric
constructions the laid-in yarns play the main role, the loops only link
them together.
There are a great number of end uses for these fabrics. Biaxial fabrics
with PVC coating, for instance, are used for manufacture of stressed
roof constructions by which very wide spaces can be covered. Fabrics
with directed behaviors are available also as reinforcement materials of
composites or for geogrids.
3.1.5 Medical treatment Many kinds of textiles are used in medical
treatment. It is not surprising that a great
part of clothing worn by doctors and nurses
in hospitals and clinics is product of the
knitting industry (e.g. undershirts, socks).
But sometimes they are not conventional
ones, they are made from yarns or with
finishing that make them antibacterial
against infections or against of rising of
unpleasant sweaty smell. Various types of bandages (both rigid and
elastic), surgical stockings, certain parts of
orthopedic equipment (or theses) (like knee-
, wrist- and elbow-braces, calf and lumbar
Fig. 13 Artificial blood
vessel
Fig. 12 surgical mesh
supports, etc.) are also made by knitting technology. An important
application field for spacer fabrics is manufacturing of mattresses for
beds, operating tables and wheel-chairs. Knitted products find
application field also among implants: artificial blood vessels (they can
be circular knitted or warp knitted, the latter is made on double needle
bar raschel machine and can be made also in Y form), surgical meshes
(made on tricot machine), coverings of artificial heart valves.
Structure of the textiles used as implants is determined by its material
composition, fibers behavior and features of degradation. Materials of
sutures and implants having biologically good
properties, designable absorption and
degradability and that endure the sterilization
process are continuously subjects of research. At
the same time, continuous development of textile
technologies and machines enables to develop
newer and newer methods in surgery and
medical treatment. For this mutual development
textile technologists and doctors must closely
cooperate, while all the
Administrative procedures concerning
manufacturing and trading of such products must be strictly respected.
3.1.6 Construction Industry Construction industry is a great market for
textiles and also for knitted fabrics among them.
Around buildings being under construction or
renovation the scaffold is usually covered by
raschel-knitted net made of polypropylene foil
tapes. Knitted fabrics can be used also to
reinforce wall coverings, both outside and
inside. Some types of geotextiles and geogrids
are also knitted structures, as mentioned above.
Many buildings, and not only provisional ones,
have roofs made of textile fabrics (sports
stadiums, air terminals, halls for various
functions, etc.). If this roof is made from knitted fabric bi- or multiaxial
knitted structures are used with waterproof and weatherproof coating.
Fig. 14 artificial heart
valve
Fig. 15 knitted net
used for
construction
purpose
Huge areas, many hundreds of square meters can be covered by such
fabrics.
Another possible application of knitted fabrics in construction is textile
reinforced concrete. There are warp knitted structures developed
especially for this purpose. Textile reinforced concrete has the
advantage that it is much lighter than the one reinforced by steel bars.
3.2 Sports and functional textiles. One of the major applications of knitted
fabrics in technical textiles is in
sportswear and functional textiles. Knitted
fabrics can be conveniently made into
multi-layered fabrics with or without
finishing to get different characteristics
depending on end-use applications. For
example, cotton as a next-to-skin layer in
the presence of heavy moisture between
the skin and the fabric will not be able to
wick away the moisture immediately. This
will result in clinginess and uneasy
comfort level. However, if the next-to-skin layer is a synthetic
material such as polyester, moisture will be wicked away
instantaneously resulting in dry skin.
The adjacent layer next to the synthetic
layer can be typical cotton knit which
will be able to absorb the moisture.
Such multi-layer knitted structures can
increase the comfort and performance
level of athletes.
Recently an interesting project was
undertaken at Texas Tech University to
develop highly breathable knitted fabrics. This project looked at the
possibility of identifying different varieties of cotton, which will give
enhanced moisture transport. This way, if suitable cottons were
identified that have superior breathability characteristics, these
cottons can be selected to develop highly breathable sportswear and
performance fabrics. Results showed that chemistry of cotton, in other
Fig. 17 Indian cricket team
shirt
Fig. 16 functional textile
words the constituent sugar types in cotton influenced the structure of
cotton and hence the transport of vapor through them. This project
identified certain sugars in cotton fiber, which provide good
breathability characteristics. This project showcases the impact of
multidisciplinary research involving agriculture and engineering
disciplines to develop next generation functional knits.
Knitted fabrics can be surface
enhanced by different methods such
as brushing, calendaring,
embossing, and plasma
functionalization to impart a myriad
of functionalities. Knitted fabrics
when raised by calendars can give
bulkiness, which will enable them to
be used as blankets for providing
necessary warmth in cold environments. Similarly, plasma
functionalized knitted fabrics can have different characteristics such
as water absorbency, water repellency and oil repellency and so on.
Another application of knitted fabrics in the industrial set-up is its use
in the automobile industry. Warp knitted fabrics are preferred as
headliner fabrics in the luxury automobiles. Predominantly, they are
made from polyester and blends of polyester and spandex. Nylon can
also be used depending on the end-use
requirements. Depending on the requirements,
the face fabric can range from 80-300 grams
per square meter.
Knitted fabrics on their own can find technical
textile applications. These fabrics can also be
made into multi-layer composites involving
knits, woven and nonwoven fabrics giving
them different characteristics. In addition,
knitted fabrics can also be chemically modified
and finished to get a number of diffe rent end-
use characteristics. It is up to the knitted fabric
producer to use a number of processes both
mechanical and chemical to enhance the use
and sales values of knitted fabrics.
Fig. 19 use of net in NIKE shoe
Fig. 18 taekwondo
clothes
3.3 Knitted fabric for clothing
Clothing is the most popular item to make
with knits because of the many varieties of
knit fabrics available. Use jersey, which is a
single knit, to make clothing with a soft, fluid
design, suggests Claire Shaeffer in her book
"Claire Shaeffer's Fabric Sewing Guide,"
such as dresses, T-shirts, soft jackets and
coats. Use double knits to create jackets,
coats and pants. Interlock knits are suitable
for evening wear and lingerie. Tricot is
perfect for active wear, such as leotards and
bathing suits. Sweater knits can be used to
make tops, sweater dresses and skirts.
In fact knitted fabrics plays very important roles in our day to day life.
Here are some illustrations showing the daily uses of knitted clothes:-
Fig. 20 men’s casuals
Fig. 21 baby’s hand
knitted jersey
Fig. 22 warm
clothing for
winters
Fig. 23 warm
cloths for new
borne
Fig. 25 legging and
stockings for casual
wears
Fig. 27 tee shirts
Fig. 26 knitted flexible
shoes for babies (hard
socks)
Fig. 24 female clothing
(net)
4. The scope of knitted fabric/clothes
In a rapidly changing world - where demand
and supply opportunities change equally fast -
it is not enough to simply project the present
into the future. Alternative visions of the future
are needed in order to broaden understanding of
issues that should be addressed today. Building
scenarios that describe the world six years from
now is necessary in order to adapt current
practice and arrive at a more robust, future-
oriented practice should a particular future
occur.
With the advancement of the knitting
technology, the use of knitted fabrics is
expanding rapidly all over the world. The
Knitwear sector and its markets are constantly evolving worldwide.
This segment of the garment industry has experienced many changes
in recent years. With improved technology, the limitations like
shrinkage and torque in knitted fabrics or garments have been reduced
to a great extent and this has opened more opportunities.
Many global players are eyeing the Indian Market with great interest
as one of leading markets in the Post Quota Scenario. The Knitwear
Exporters from all over India like from Delhi, Mumbai, Bangalore,
Chennai and Tirupur have already been equipped with making new
designs and collections which complements with the current fashion
trend and to meet with International Buyers’ requirements. Tirupur is
one of the few Indian towns that took advantage of globalization and
economic reforms, along with export-led growth. The export of
knitwear products from Tirupur is always on the rise every year and
the industry continues to show rapid growth.
There are many reasons for the growth of the India knit garment
industry. These are as follows:
Fig. 28 the future of
knitting industry
Compared to the setting up of other fabric producing industries,
the capital investment for starting a new knitting unit is
relatively small.
The high productivity of knitting machine is also an important
factor for the growth of the industry.
As the preparatory process for knitting is less than weaving, the
time required to get an order completed is less than that required
in the case of woven fabrics.
The setting up of knitting machines to produce a given type of
fabric is a fast and simpler operation than the setting up of a
loom.
Knitting is more flexible than weaving in the sense that styles
and designs can be changed with unparalleled rapidity. Knit
garments are geared to quick turnover in keeping with the rapid
fashion changes in the apparel market.
There are wide varieties of new yams that have brought new
standards of performance and new aesthetics into the knit
market.
The knit fabrics are very comfortable and are in tune with the
times.
The present generation demand wrinkle-free, ease-of-care
fabrics and knit garment is the perfect solution for this. The
recent success of knit garments has been greatly due to their
easy-care properties.
Knitted garments generally require no ironing and are therefore
it is cool for traveling persons.
Knitted fabrics are the most comfortable ones for swimwear and
sportswear.
All problems related with labor organization like wages,
benefits to labor etc. are reduced in the knitting industry because
knitting units require very less labor.
The machinery manufacturers with the aim of high productivity
and versatility have developed highly innovative machinery
which has also led to the boom in the knitting industry.
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