Introduction to Textile Fabric Part 1: Basic Knitted Fabrics

Introduction to Textile Fabric
Part 1: Basic Knitted Fabrics
By Hammad Mohsin
Department of Textiles, UMT Pakistan
Courtesy: Dr. Jimmy Lam
Institute of Textiles & Clothing The Hong Kong Polytechnic
University
Content
zDifference between woven and knitted
fabric
zSingle Knit Fabric
{Properties and Characteristics
{Knitting Notation
zBasic loop (knit, tuck and miss)
1
Difference between woven and knitted
fabrics
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
z
2) Elasticity
{ 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.
2
Difference between woven and knitted
fabrics
z
3) Fabric Density and Cover
{ 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
z
4) Thickness and Handle
{ Knitted fabric is much thicker and softer than
woven fabric as it has a complicated 3dimensional 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)
3
Difference between woven and knitted
fabrics
z
5) Production Cost
{ 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
z
6) Fabric Application
{ 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
4
Single Knit Fabric
What is single knit fabric
z Single knit fabric or single jersey is a general
term for knitted fabrics produced by the knitting
machines using one set of needles only.
z The fabrics could be composed of different
patterns, stitches, materials and different
weight and thickness.
5
General Characteristics of Single Knit
Fabric
1)
•
•
•
•
•
Fabric Elasticity
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 deterioriate 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
General Characteristics of Single Knit
Fabric
1) Fabric Elasticity
z A loop is a very short
length of yarn bent
into a OMEGA shape
as shown on the
black area
6
General Characteristics of Single Knit
Fabric
1)
Fabric Elasticity
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
{
{
{
•
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.
.
7
General Characteristics of Single Knit
Fabric
2) Edge Curling
The curling on the fabrics edges is one of the
disadvantages of single knit fabircs.
{ It gives problems to the cutting, sewing and linking
processes.
{ Edge curling can be reduced by the following:
z
z
•
Wet finishing, high temperature treatment like sourcing,
bleaching and dyeing can remove the torque in the
yarn and fabric.
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.
8
General Characteristics of Single Knit
Fabric
3) Laddering
Laddering is a fabric fault which affects the
fabric appearance. Laddering will easily
occur when:
z
z
z
z
z
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.
9
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