Yarn is an assemblage of fibers that is twisted or laid together so as to form a continuous strand that can be made into a textile fabric. So a yarn is a strand of natural or man made fibers or filaments that have been twisted or grouped together for use in weaving, knitting or other methods of constructing textile fabrics. The type of yarn to be manufactured will depend on the fibers selected, the texture, or hand of the fabric to be made and qualities such as warmth, resiliency, softness and durability required in the fabric's end uses.
Different Types of Fibers:
All the textile fibers are classified into tow categories such as staple fiber and filament.
Staple Fibers: It has a limited length that varies according to the type, such as cotton, wool, jute etc. There are two types of staple fiber, one is short staple fiber and another one is long staple fiber. Cotton is mainly short staple fiber and other maximum natural fivers are long staple except silk which is a natural filament fiber.
Filament Fibers: It has continuous length that means the length of filament is equal to the length of yarn. All man made fibers are filament. Man made or synthetic fivers are produced as filament, though they are used as staple fibers if necessary. So filament fibers are used as staple fiber but staple fibers can't use as filament.
Classification of Textile Yarns:
Based on the structure the yarns are classified into three categories.
Staple Fiber Yarns(Spun Yarns): Spun yarns are produced by mechanical assemble and twisting together (spinning) of staple fibers. Ring spinning, Rotor spinning, Wrap spinning, Air-jet spinning etc. machines are used to produce the spun or single yarns.
Ply Yarns: Single yarns are used in the majority of fabrics for normal textile and clothing applications but in order to obtain special yarn features, particularly high strength and modulus for technical and industrial applications, ply yarns are often needed. A folded or ply yarn is produced by implying twist two or more single yarns together in one operation and a cabled yarn is formed by twisting together two or more folded yarns or a combination of folded and single yarns.
The Twisting together of several single yarns increases the tenacity of the yarn by improving the binding -in of the fivers on the outer layers of the component single yarns. Ply yarns are also more regular, smoother and more hard wearing, The direction of twisting is designed as S or Z, just as in single yarns. Normally the folding twist is in the opposite direction to that of the single yarns.
Filament Yarns: A filament yarn is made from one or more continuous strands called filaments where each component filament runs the whole length of the yarn. Those yarns composed of one filament are called monofilament yarns and those are containing more filaments are called multifilament yarns. For apparel applications a multifilament yarn may contain as few as two or three filaments or as many as 50 filaments. In carpeting, for example, a filament yarn could consist of hundreds of filaments. Most manufactured fibers have been produced in the form of a filament yarn. Silk is the only natural filament yarn.
According to the shape of the filaments in the yarn, filament yarns are classified into two types, flat and bulk. The filaments in a flat yarn lie straight and neat and are parallel to the yarn axis. Thus, flat filament yarns are usually closely packed and have a smooth surface. The bulked yarns, in which the filaments are either crimped or entangled with each other, have a greater volume than the flat yarns if the same linear density.
Texturing is the main method used to produce the bulked filament yarns. A textured yarn is made by introducing durable crimps, coils, and loops along the length of the filaments. As textured yarns have a increased volume, the air and vapour permeability of fabrics made from them is greater than that from flat yarns. However, for applications where low air permeability is required such as the fabrics for air bags, flat yarns may be a better choice. Textured yarns are used for stockings and tights, swimwear, sportswear, outerwear, underwear, carpets, sewing and overedge stitching threads for extensible fabrics.
Classification of Textile Yarns According To Their Use:
Based on their uses it can be classified into two types.
Weaving Yarns: Yarns for the woven cloth are prepared for the intended end use. Yarns to be used in the warp, the lengthwise direction of cloth, are generally stronger, have a tighter twist, and are smoother and more even than are yarns used for filling, the cross wise direction of a cloth. Novelty yarns may be used in the warp, but they are generally found in the filling. Highly crepe yarns are usually found used as filling yarns.
Knitting Yarns: These can be divided into yarns for hand knitting and yarns for machine knitting. Knitting yarns are more slackly twisted than yarns for weaving. Hand knitting yarns are generally plied whereas those for machine knitting can be either simple or multi plied.
