Introduction to Textile Fabric Part 3: Double Knit Structures Dr. Jimmy Lam Institute of Textiles & Clothing The Hong Kong Polytechnic University

Content What is double knit fabrics Characteristics of double knit fabrics Examples of double knit fabrics: 1X1 Rib, 2 x 2 rib, half cardigan, full cardigan, half milano and full milano. Interlock Fabric Modified interlock fabrics

Double Knit Fabric Double knit fabrics or double jersey are knitted fabrics produced by machines using two set of needles. They can be produced by: Rib and non-jacquard machines Interlock machines

General Characteristics (Double knit fabrics) Fabric Appearance It takes two set of needles to produce a piece of double knit fabric; each set of needles produce their own loops on one side of fabric. Balance of structure As double knit fabrics have loops on both sides, curling is not so worse as single knit structure.

General Characteristics (Double knit fabrics)2 Fabric Weight and thickness Double knit fabrics are generally heavier and thicker than single knit fabrics because the number of loops per unit area is much more on double knit fabrics. Factors affect the fabric weight and thickness are: Yarn count and machine gauge; Fabric structure; Stitch density and Type of finish. Fabric elasticity The elasticity of double knit fabrics is mainly affected by their structures. Normally double knit fabrics are more elastic than single knit fabrics.

The rib and non-jacquard structures

The rib structure All structures of this group are produced by two sets of needles with the opposite needles off set for half a needle space; Ie. The head of the needles are not directly facing each other.

Rib Gating

Example of double knit fabric : 1x1 rib This is the most simple double knit structure. It can be made on V-bed knitting machine and circular rib machine. 1x1 rib fabric is one course per repeat structure. Both face and back looks exactly the same.

Characteristics of 1x1 rib The 1x1 rib is a perfectly balanced structure. The torque in the yarn is neutralized by the loops forming on the two side of the fabric alternatively; no curling will occur on the edge. The elastic recovery of 1x1 rib fabric is exceptionally high along the width. When relaxed the fabric shrunk so much that only the technical face loops can be seen on both sides.

End uses of 1x1 rib Underwears Sweater Waist Band It is common to use this structure for men’s underwear such as the vest, knitted on 16 gauge with 20Ne cotton This gives a light weight and elastic fabric of 100-120 g/m2. Sweater In the cut and sewn knitwear group, 1x1 rib of the medium gauges (7-12) knitted on wool or acrylic yarns are for ladies’ jumper. For example 2/32 Nm acrylic yarn on 12 gauge machine. Waist Band The rib cuff, waist band or neck strap of the sweaters are usually 1x1 rib structure. All the rib top of socks are 1x1 rib plus rubber inlay.

Examples of double knit 2x2 rib and broad ribs Similar to 1x1 rib, this is also an one course per repeat structure. The main difference is that it is composed of 2 technical face loops and 2 back loops per repeat along the course. The 2x2 rib is most popular for the cuffs and waist bands for the coarse gauge knitwears.

2x2 rib

2x2 ribs There are two methods to produce 2x2 ribs on knitting machine Method 1: with every 3rd needles out of action Method 2: with every 3rd and 4th needles out of action.

2x2 rib The fabrics produced from these two methods are more or less the same. Method 1, however, gives a tighter fabric and more elastic fabric. This method is used on circular rib machine and V-bed machine. Sometimes, the rib is called 2x1 rib Method 2 is a true 2x2 rib and is used on purl machine and double cylinder only.

Yarn Path diagrams This is another method to represent the loop formation sequence of a knitted fabric. The yarn path diagram is very easy to understand, especially when it is used on double knit structures.

Yarn Path Notation

The broad ribs (fancy ribs) Any rib which is wider than 2x2 rib can be classified as broad ribs or fancy ribs. Example the Derby rib which is 6x3 rib is generally used on the pullovers. Fancy rib can be of any combination in face and back wales, such as 10 x5; 20 x 4 etc

Fancy Rib (broad rib)

Discussion What is double knit fabric? Which fabric is more elastic, plain or 1x1 rib fabric?