Introduction to Textile Fabric Part 1: Basic Knitted Fabrics

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Introduction to Textile FabricPart 1 Basic
Knitted Fabrics

• Dr. Jimmy Lam
• Institute of Textiles Clothing
• The Hong Kong Polytechnic University

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Content

• Difference between woven and knitted fabric
• Single Knit Fabric
• Properties and Characteristics
• Knitting Notation
• Basic loop (knit, tuck and miss)

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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.

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Difference between woven and knitted fabrics

• 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.

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Difference between woven and knitted fabrics

• 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.

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Difference between woven and knitted fabrics

• 4) Thickness and Handle
• 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)

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Difference between woven and knitted fabrics

• 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)

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Difference between woven and knitted fabrics

• 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

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Single Knit Fabric
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What is single knit fabric

• 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.

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General Characteristics of Single Knit Fabric

• 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

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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

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General Characteristics of Single Knit Fabric

• 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.

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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.
• .

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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
• 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.
• .

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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.

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General Characteristics of Single Knit Fabric

• 3) Laddering
• Laddering is a fabric fault which affects the
  fabric appearance. Laddering will easily occur
  when
• 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.

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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.

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Discussion

• Discuss the difference between woven fabrics and
  knitted fabrics
• Discuss the general characteristics of single
  knit fabrics