a) Fibres: spinning and fibre production, spinning (melt, dry & wet); elastomers: calendering, reinforced plastics & laminates: composites, molding & its types, casting extrusion and coating.
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Fiber:- Fiber or fibre is a natural or man-made substance that is significantly longer than it is wide.
- Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.
- Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts.
Synthetic fibers
- Synthetic come entirely from synthetic materials such as petrochemicals, unlike those man-made fibers derived from such natural substances as cellulose or protein.
- Fiber classification in reinforced plastics falls into two classes: (i) short fibers, also known as discontinuous fibers, with a general aspect ratio (defined as the ratio of fiber length to diameter) between 20 and 60, and (ii) long fibers, also known as continuous fibers, the general aspect ratio is between 200 and 500.
Conversion of Fibre to Yarn (Thread)
Spinning Yarns: The process of converting cotton fibres from ginned lint into a yarn involves a number of processes that aim to clean, remove short fibres, align fibres and ultimately spin the yarn and prepare it for delivery.
Ginned: separated cotton from seed
Lint: Raw cotton after ginning is called lint Or Cotton fiber after separated from the seed is called lint
Blow room:
Blow room is the initial stage in spinning process. The name blow room is given because of the "air flow" And all process is done in blow room because of air flow. Blow room is consisting of different machines to carry out the objectives of blow room. In blow room the tuft size of cotton becomes smaller and smaller.
Carding:
Carding is a mechanical process that disentangle (free (something or someone) from something that they are entangled with), cleans and intermixes fibres to produce a continuous web or sliver suitable for subsequent processing. This is achieved by passing the fibres between differentially moving surfaces covered with card clothing. It breaks up locks and unorganised clumps of fibre and then aligns the individual fibres to be parallel with each other.
Combing:
Combing is a method for preparing carded fibre for spinning. The process of combing is accompanied by gilling, a process of evening out carded or combed top making it suitable for spinning. Combing separates out short fibres by means of a rotating ring or rectilinear row of steel pins.
Drawing:
Drawing, also called Drafting, in yarn manufacture, process of attenuating the loose assemblage of fibres called sliver (q.v.) by passing it through a series of rollers, thus straightening the individual fibres and making them more parallel. Each pair of rollers spins faster than the previous one.
Drawing reduces a soft mass of fibre to a firm uniform strand of usable size. In the production of man-made fibres, drawing is a stretching process applied to fibres in the plastic state, increasing orientation and reducing size.
Roving:
Sliver (untwisted textile fibres) obtained from draw frame if further processed in roving frame. Roving process is the last second stage of spinning process conducted after blow room, carding, combining, drawing and prior to cone winding (twisting). Overall, the roving operation in textile manufacturing process focuses in decreasing the density of sliver from draw frame by draft. After the reduction of linear density this sliver is transferred to roving where fibers become suitable for spinning. Roving process can be stated as an initial step where twist is inserted for producing yarn in spinning mills.
Yarn:
Yarn consists of several strands of material twisted together. Each strand is, in turn, made of fibers, all shorter than the piece of yarn that they form. These short fibers are spun into longer filaments to make the yarn. Long continuous strands may only require additional twisting to make them into yarns.
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Melt spinning:
Melt spinning is the most economical process of spinning due to the fact that no solvent is recovered or evaporated just like in solution spinning, and the spinning rate is fairly high. Melt spinning is the preferred method of fabricating polymeric fibers and is used extensively in the textile industry.
Melt spinning is used for polymers that can be melted easily. In this process, a viscous melt of polymer is extruded through a spinneret containing a number of holes into a chamber, where a blast of cold air or gas is directed on the surface of fibers emanating from the spinneret. As the air strikes the fibers, the fibers are solidified and collected on a take-up wheel.
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Different spinning methods are available in making yarns, including ring-spun, rotor-spun, twistless, wrap-spun and core-spun yarns.
Ring-spun yarns: This is the most widely used method of staple-fibre yarn production. The fibres are twisted around each other to give strength to the yarn.
Rotor-spun yarns: These are similar to ring-spun yarns and usually made from short staple fibres. They produce a more regular and smoother, though weaker, yarn than ring spinning.
Twistless yarns: The fibres are held together by adhesives, not by the twist, and are often laid over a continuous filament core.
Wrap-spun yarns: These yarns are made from staple fibres bound by another yarn, which is usually a continuous man-made filament yarn. The yarns can be made from either short or long staple fibres.
Core-spun yarns: Core-spun yarns have a central core that is wrapped with staple fibres, and are produced in a single operation at the time of spinning. For example, a cotton sheath for handle and comfort, with a filament (often polyester) core for added strength; or cotton over an elastomeric core.
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