Transcript Knitted Fabric Studies - CEResources

Introduction to Textile
Fabric
Basic Knitted Fabrics
Dr. Abu Yousuf
Department of Chemical Engineering & Polymer Science
Shahjalal University of Science & Technology
Sylhet-3114, Bangladesh
Knitting
• Knitting is a method by which thread or yarn may be turned
into cloth or other fine crafts. Knitting consists of
consecutive loops, called stitches. As each row progresses, a
new loop is pulled through an existing loop. The active
stitches are held on a needle until another loop can be
passed through them. This process eventually results in a
final product, often a garment.
• Knitting may be done by hand or by machine. There exist
numerous styles and methods of hand knitting.
How to cast on
Casting on is simply the way that you get stitches onto the needle so
that you can start knitting.
Stitch: A single loop of yarn around an implement
such as a knitting needle
Difference between woven
and knitted fabrics
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1) Fabric Construction
– Woven fabric is at least made
up of two separate groups of
yarns (warp and weft) and
knitted fabric can be made up
of one yarn only.
– Weaving is interlacing of 2 set
of yarn to form a fabric.
– Knitting is a process of
converting yarn to fabric by
forming a series of loops
dependent on each other.
Difference between woven
and knitted fabrics
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2) Elasticity
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Elasticity is the ability
of the fabric to extend
and recover to its
original shape and
length.
Knitted fabric has
higher extensibility and
instant recovery ability
than woven fabric. up
of one yarn only.
Difference between woven
and knitted fabrics
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3) Fabric Density and Cover
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In general, woven fabric can be produced
in extremely tight and higher coverage
when compared with knitted fabric.
Range of density variation is much higher
than knitted fabric.
Knitted fabric in general, is looser in
structure.
Difference between woven
and knitted fabrics
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4) Thickness and Handle
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Knitted fabric is much thicker and softer
than woven fabric as it has a complicated
3-dimensional structure.
Knitted fabric seems to be softer
because the knitted loops are more easily
compress and extensible than straight
yarn (warp and weft in woven fabric)
Difference between woven
and knitted fabrics
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5) Production Cost
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Weaving requires expensive preparation
processes like warping, sizing, draw-in;
while knitting only requires yarn waxing.
The production rate of circular knitting is
roughly FIVE times faster than modern
weaving loom. and weft in woven fabric)
Difference between woven
and knitted fabrics
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6) Fabric Application
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The popularity of sportswear, hosiery,
underwear and high fashion knitwear
make a strong demand on knitted fabric
every year which cannot be replaced by
woven fabric.
However, if fabric requires good
dimensional stability, high tenacity like
trousers, jackets, canvas, woven fabric is
the right choice
Tenacious: Holding together firmly
Single Knit Fabric
What is single knit fabric
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Single knit fabric or single jersey is a
general term for knitted fabrics
produced by the knitting machines using
one set of needles only.
The fabrics could be composed of
different patterns, stitches, materials
and different weight and thickness.
Stitch:A mode of arranging the threads
in sewing, knitting, or crocheting
General Characteristics of
Single Knit Fabric
1) Fabric Elasticity
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The single knit fabrics are composed of loops linking
with each other on the two sides as well as on the two
ends.
The shape of a loop can easily be changed by
stretching the fabric in all directions.
The elasticity of knitted fabrics makes them
favorable for sports’ wear, casual wear and hosiery.
This elasticity, however, will be deteriorate due to
over stretching, washing or ageing and eventually, the
loops cannot recover to its original shape.
This change of shape is called distortion or poor
dimensional stability
hosiery
General Characteristics
of Single Knit Fabric
1) Fabric Elasticity
• A loop is a very
short length of
yarn bent into a
OMEGA shape as
shown on the black
area
General Characteristics
of Single Knit Fabric
1) Fabric Elasticity
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The dimensional stability of single knitted
fabrics can be improved by:
Increase the fabric density, by using smaller loop
length to give the fabric higher cover factor.
Warp and weft insertion, by inserting straight yarns
to the fabric and bind the loops together to reduce
their freedom of movement
Apply resin finishing, a resin chemical can set the
fibres and loops on fabric.
Use the thermal plastic yarns, man-made fiber like
polyester or nylon can be set at high temperature
and maintain the loop shape on knitted fabrics.
General Characteristics
of Single Knit Fabric
2)
Edge Curling
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Almost all single knit fabrics will
curl on the edges when cut.
It is the unbalanced loop
structure and the yarn torque
inside the fabric which tends to
recover the original shape of the
yarn.
It is the edges of a piece of
fabric that is free for movement,
therefore, the edges curl.
.
General Characteristics
of Single Knit Fabric
2) Edge Curling
The curling on the fabrics edges is one of the
disadvantages of single knit fabircs.
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It gives problems to the cutting, sewing and linking
processes.
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Edge curling can be reduced by the following:
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Wet finishing, high temperature treatment like
sourcing, bleaching and dyeing can remove the torque in
the yarn and fabric.
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Stentering or steam pressing, stentering is used on
open width piece goods, and steam pressing for
knitwear panel and garment.
General Characteristics
of Single Knit Fabric
3) Laddering
When a loop in the fabric is
broken, the loop directly
underneath it will slip off and
become a short length of
horizontal line instead of
maintaining the OMEGA
shape.
If a vertical row of loops slip
off from the fabric, it looks
like ladder.
General Characteristics
of Single Knit Fabric
3) Laddering
Laddering is a fabric fault which affects
the fabric appearance. Laddering will easily
occur when:
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The fabric is loosely knitted;
The yarn frictional index is low;
The fabric is plain knit;
There is a big knot in yarn during knitting;
The needle head is broken.
General Characteristics
of Single Knit Fabric
4) Fabric Appearance
All single jersey fabrics have
different appearance on two sides
Looking on the face side, the fabric
seems to be composed by thousands
of “V” loops; while on the back side,
the loops appear to be semi-circles.