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Fibers, Yarns & Threads

FibersFibers, Yarns and Threads, in that order, are the most basic requirements of the Textile Industry. Different kinds of fibers are used as raw materials to make yarns and threads. These yarns and threads are then used for manufacturing finished textile goods.

Fiber is a threadlike strand which is used for spinning yarn. On the basis of source, fibers are classified as natural and man made or synthetic fibers. Natural fibers like cotton, silk, linen, wool etc. are obtained from natural products. Synthetic fibers like fiberglass, nylon, rayon etc. are artificially made. They are usually long-chain polymers, produced industrially by the condensation of many small units.

On the basis of composition, fibers have two categories - Filament and Staple Fibers. Filament Fibers, further classified as Mono filaments and Multi filaments are of continuous length and measured in yards or meters. Staple Fibers are short fibers and are measured in inches. On the basis of usage, fibers are classified as textile, cordage, brush, felt, filling, and plaiting fibers.

Natural Fibers
Natural fibers are obtained from plants, animals and geological processes. They can be classified as Plant Fiber, Animal Fiber and Mineral Fiber.

CottonPlant fibers include cotton, flax, jute, bamboo, ramie, kapok, hemp and sisal among others. Flax is the oldest known fiber crop and is used for linen production. Cotton Fiber, obtained from the seeds of the cotton plant, is the most widely used natural-fiber. Jute Fiber is the cheapest and strongest of all natural fiber and ranks second in production after cotton. It is used in traditional packaging fabrics, carpet backing, mats, bags, tarpaulins, ropes and twines etc. Bamboo Fiber is environment-friendly and is sometimes mixed with cotton or other raw materials. It is mainly used for bathrobes, towels, foot mats, bed clothes, underwear, close-fitting T-shirt, stockings etc. Kapok, obtained from a tropical tree is used as stuffing, especially for life preservers, bedding, upholstery, and for insulation against sound and heat. Hemp is used for making various kinds of cordage, canvas and other cloths.

Natural FibersWool fiber and silk fiber are the most widely used Animal Fibers. Wool is derived from the fur or hair of animals like sheep, goats, llamas and rabbits and then coated with an oil, lanolin, which is waterproof and dirt proof. Silk is a protein fiber obtained from the cocoon of silkworm. It is smooth, shiny with sleek texture.

Asbestos has long, thin fibrous crystals and is the only naturally occurring long mineral fiber. It is resistant to heat, electricity and chemical damage. Other Mineral Fibers include Wollastinite, Attapulgite and Halloysite which are short, fiber-like minerals used for sheeting, stage curtains, and fire blankets.

Man-made fibers
Man-made fibersThe fibers which are artificially made by various chemical compositions are man-made or synthetic fibers. Some of them are manufactured from natural cellulose, including rayon, modal, and Lyocell. Nylon is a made from diamines and dicarboxylic acids and is used in many fabrics, mosquito netting, rope, and tire cords. Rayon is made from cellulose of cotton linters and wood pulp. Fiberglass is made from molten glass. It is strong, durable, and impervious to many caustics and to extreme temperatures and are used for curtains, drapery and for industrial purposes.

ThreadsYarnis a continuous length of interlocked fibers used for manufacturing textiles. It is prepared by spinning. Spinning is the twisting together of fibers to form yarn (or thread, rope, or cable). Earlier fiber was spun by hand using simple tools like spindle and distaff. Later the use of spinning wheel gained importance. Industrial spinning started in the 18th century with the beginning of the Industrial Revolution. Hand-spinning remains a popular handicraft.

Yarn is made of staple ( short) fibers through several techniques including Ring, Open- End, Friction, Jet, Vortex, Centrifugal spinning etc. Ring method is the oldest and the most used technique. Open- end spinning is another important method. The basic manufacturing process of spinning includes carding, combing, drafting, twisting and winding. As the fibers pass through these processes, they are successively formed into lap, sliver, roving and finally yarn.

Ring Spinning
Ring SpinningThe raw fiber arrives at a spinning mill as compressed mass which goes through the processes of blending, opening and cleaning. Carding is the initial straightening process which puts the fiber into a parallel lengthwise alignment. Now the fiber is called 'Lap'. The lap is treated for removing the remaining trash, disentangling and molding it into a round rope like mass called 'Sliver'. The sliver is then straighten again which is called Combing. In this process, the short fibers are completely separated from the longer fibers. Drawing pulls the staple lengthwise over each other. After several stages of drawing out, the sliver is passed to the spindles where it is given its first twist and is then wound on bobbins. 'Roving' is the final product of the several drawing-out operations. The roving, on bobbins, is placed in the spinning frame, where it passes through several sets of rollers running at high speed and finally the 'Yarn' is produced of the sizes desired.

Open- End Spinning
Open- End SpinningOpen- End Spinning is a relatively new development. It begins with the carded sliver which is put into rollers. These rollers revolve at a faster speed. As a result, the sliver is completely opened up. The separated fibers are moved by an air stream and are collected as a thin layer in a groove on the inner surface of a funnel- shaped rotor, which rotates at a very high speed. There, it is spun around into yarn.

Sewing threads are made for efficient, smooth stitching that will not break or become distorted for the life of the sewn product. Its main function is to hold together parts that could be of textile, leather etc to form garments or other end products. Sewing machines are used to join the parts with the sewing thread in a process called Sewing.

Industrial Sewing is an extremely high-speed operation which does up to 12,000 stitches per minute. Various forces such as braking force, thread tightening, extremely high temperatures etc. are exerted on threads during sewing. Thus, sewing thread finishing becomes important as the finishing agents impart certain properties to the sewing thread. The traditional finishing agents include Paraffin wax, Silicones, Anti static agents etc. Finishing through these agents is done by various methods such as Lick roll method, Dye bath lubrication, Dip tank lubrication, Solid wax lubrication etc.

Assessment of Thread Quality
YarnThe performance of sewing thread is affected by its Count, Strength and Tenacity, elongation, Sewability, etc. Count indicates the mass per unit length of the thread i.e., Linear density. The ease with which a sewing thread can penetrate a fabric is determined by its frictional characteristics. Friction is largely determined by the quality of lubrication as it allows the passage of the sewing thread within the bobbins and needle of the sewing machine and further gives an easy passage between the fibres and yarns in the fabric.

A large number of tests are available for assessing the quality of sewing threads. The most common tests conducted by the manufacturers and users are physical and fastness properties. However, the most critical test for sewing thread is the sewability in the dynamic conditions.

Generally the sewing threads are tested by two methods - Physical Test and Chemical test. Physically a thread is examined for thread count, thread diameter, shrinkage, hairiness, thread friction, unevenness and imperfections, tensile strength and elongation, loop and knot strength, abrasion resistance and UV radiation resistance. Chemical testing is done for examining properties like color fastness to washing, dry cleaning, water migration and color matching

Although threads usually represent much less than 1% by mass of apparel yet its quality requirement is very stringent, both during the sewing process itself, and during the subsequent life of the end product. Thus testing of sewing thread is important from the point of view of quality control, process control, product development and process optimization.