What is Warp Knitting?
Warp knitting is a loop-forming knitting process where many yarns run parallel to each other and form loops in an interlocked zigzag pattern. The face has vertical loops, but they are positioned at a slight angle whilst the back has horizontal floats, which identifies it as a warp knit. As this type of knit structure uses a number of yarns, they have to be guided to the needles being used otherwise they will get tangled. Warp knitting is known for being fast, stable, and versatile, producing fabrics suitable for a wide range of applications.
Types of Warp Knitting | Fabric Produced by Warp Knitting
1. Lock-Knit:
Lock-Knit is the most common type of warp knitting. It has two vertical loops on the face and two needle underlaps on the back to provide sheen. It is usually made from synthetic filament yarns, which produces a fabric with a distinctive zigzag on the back. It has a locked knit, so it doesn’t ladder, and it has vertical wales on the front. As the fabrics have lustre and a soft handle, they are used for underwear, linings and sports shirts. The polyamide fabric of the 1960s, Crimplene, used this technique. If the lapping movement is reversed, the underlaps appear on the back and trap the longer fibres, which make the fabric less flexible and less prone to shrinkage in the width. Sharkskin is produced using this technique, and the underlaps are extended to provide better stability and opacity.
2. Tricot:
It is another common type warp knitting, characterized by fine vertical wales on the face and crosswise ribs on the back. Tricot derived from the French word Tricoter meaning to knit, the tricot machine uses compound or spring-bearded needles with eighteen to forty needles per 2.5cm on either a single or double needle bed. It contains anywhere between two and five guide bars to move the threads from one needle to another to ensure that the loops are held to form the fabric. These machines work at high speed, producing anywhere between 2,000 and 3,500 courses per minute. The fabric widths vary from 213cm to 533cm. A number of yarns are used, and the greater the number, the greater the design flexibility. Also, the number of loops in both course and wale affect the fabric; the higher the loop count, the greater the fabric’s strength. Tricot knits are usually made of synthetic filament, which allows them to produce jersey, satin and mesh fabrics. The latter are created by deactivating needles or yarns at selected design points. Dots can be created by floats behind the fabric, which are cut later. Fabrics vary based upon the use of textured yarns, which are used for outer garments; variations in colour on the warp beam and inlaid yarns (weft insertion) from a separate beam, which are held by the knitted stitches can add texture and stability to the fabric. Upholstery fabric uses a heavyweight yarn under tight tension to make the fabric very durable. A plain tricot can be napped for texture and additional warmth. The materials are often used as laminate fabrics to improve the properties of the original fabrics. Tricot knits, which are soft, have bulk, but they are lightweight, porous allowing water vapour and air from the body, crease-resistant and have good draping qualities. Therefore, a wide variety of end uses exist: lingerie, shirts, gloves, leisurewear, sportswear, swimwear, bed linen, towels, nets, medical materials and lightweight furnishings with jacquard construction for home and automotive industries.
3. Milanese (Tricot Variation):
A variation on tricot is Milanese, which has a fine rib on the face and a distinctive, diagonal line on the back of the fabric. Springbearded needles are used on a flat bed machine whilst latch needles are used on circular machines, both using filament yarns. However, Milanese is smoother, has greater elasticity and durability than tricot but is much more expensive, hence very little Milanese is manufactured.
4. Raschel:
Produces lace-like, open, or textured fabrics. It uses heavier yarns combined with finer ones. Raschel fabrics are used for coarse sacking, carpets, laces, and home textiles. Raschel machines use latch or compound needles with twelve to thirty-two needles per 2.5cm in single or double needle beds. They use anywhere between two and seventy-eight guide bars, and they can produce a wide variety of fabrics in widths ranging from 191cm to 533cm at a speed of 500 to 2,000 courses per minute. Single bed machines are used for standard Raschel, which uses two to twelve guide bars and manufactures fabric at high speed. Three to sixteen bars are used in weft insertion for industrial furnishings and curtains; twelve to forty-eight bars are used in curtain nets, corsetry and foundation garments; and up to seventy-eight bars are used in jacquard lace and more complex weft insertion for curtains. Single beds are also used for technical fabrics and structures requiring a nap. Double bed machines are used for plush, high pile, technical automotive, agricultural bags and upholstery fabrics. The main end uses of Raschel are marquisette, velvets, nets (including fishing and sporting) and upholstery fabrics, such as velvet, carpets and lingerie. It is also used in the agricultural, geotextile and medical industries.
5. Ketten or Chain Raschel (Variation):
A variation to Raschel is Ketten or Chain Raschel knit using fourteen to twenty bearded needles per 2.5cm and fabrics which are 230cm to 305cm wide. Ketten has a raised pattern effect with shell stitch that uses one or more colours. Compared to standard Raschel, the fabric is finer with greater elasticity.
6. Simplex:
This fabric comes from, effectively, two tricot machines used back to back with twenty-eight to thirty-four spring-bearded needles per 2.5cm to produce fabrics that range from 215cm to 285cm. The fine yarns produce a dense and thick fabric that shows loops on both sides, which look like a double-cloth and can be napped for a suede effect. It is used for gloves, sportswear, handbags, dense barrier fabrics and a range of stable, open work. However, this fabric makes up a small percentage of the warp knit industry.
Applications of Warp Knitted Fabrics
Warp-knitted fabrics are used in clothing, specially used in innerwear such as bras, panties, camisoles, lingerie. It is also used in sportswear, swimwear, shirts, and gloves. They are also common in home textiles such as curtains, bed linen, towels, carpets, nets, and upholstery. Industrial and technical applications include geotextiles, agricultural bags, automotive interiors, and other technical fabrics, while medical textiles include bandages and breathable protective fabrics.
Conclusion
Warp knitting is a fast, versatile, and efficient method of fabric production. It plays an important role in the modern textile industry. Warp knitting’s efficiency and fabric durability make it popular in clothing and technical applications, offering functional properties such as elasticity, shape stability, moisture management, heat retention, and antibacterial effects.
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