Spinning is a manufacturing process for creating

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

fibers. It is a specialized form of

extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex ...

that uses a

spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and a ...

to form multiple continuous filaments..

Melt Spinning

If the

is a

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...

then it can undergo melt spinning. The molten polymer is extruded through a spinneret composed of capillaries where the resulting filament is solidified by cooling.

Nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from pe ...

, olefin, polyester, saran, and sulfar are produced via this process.

Extrusion spinning

Pellets or granules of the solid polymer are fed into an

extruder Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex ...

. The pellets are compressed, heated and melted by an extrusion screw, then fed to a spinning pump and into the spinneret.

Direct spinning

The direct spinning process avoids the stage of solid polymer pellets. The polymer melt is produced from the raw materials, and then from the polymer finisher directly pumped to the spinning mill. Direct spinning is mainly applied during production of polyester fibers and filaments and is dedicated to high production capacity (>100 ton/day).

Solution Spinning

If the melting temperature of the polymer is higher than its degradation temperature, the polymer must undergo solution spinning techniques for fiber formation. The polymer is first dissolved in a solvent forming a spinning solution (sometimes called a "dope"). The spinning solution then undergoes dry, wet, dry-jet wet, gel, or electrospinning techniques.

Dry spinning

A spinning solution consisting of polymer and a volatile solvent is extruded through a spinneret into an evaporating chamber. A stream of hot air impinges on the jets of spinning solution emerging from the spinneret, evaporating the solvent, and solidifying the filaments. Solution blow spinning is a similar technique where polymer solution is sprayed directly onto a target to produce a

nonwoven Nonwoven fabric is a fabric-like material made from staple fibre (short) and long fibres (continuous long), bonded together by chemical, mechanical, heat or solvent treatment. The term is used in the textile manufacturing industry to denote fabri ...

fiber mat.

Wet spinning

Wet spinning is the oldest of the five processes. The polymer is dissolved in a spinning solvent where it is extruded out through a spinneret submerged in a coagulation bath composed of nonsolvents. The coagulation bath causes the polymer to

precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

in fiber form.

Acrylic Acrylic may refer to: Chemicals and materials * Acrylic acid, the simplest acrylic compound * Acrylate polymer, a group of polymers (plastics) noted for transparency and elasticity * Acrylic resin, a group of related thermoplastic or thermosett ...

, rayon,

aramid Aramid fibers, short for aromatic polyamide, are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic-rated body armor fabric and ballistic composites, in marine cordage, ma ...

modacrylic A modacrylic is a synthetic copolymer. Modacrylics are soft, strong, resilient and dimensionally stable. They can be easily dyed, show good press and shape retention, and are quick to dry. They have outstanding resistance to chemicals and solvents, ...

, and

spandex Spandex, Lycra, or elastane is a synthetic fiber known for its exceptional elasticity. It is a polyether-polyurea copolymer that was invented in 1958 by chemist Joseph Shivers at DuPont's Benger Laboratory in Waynesboro, Virginia, US. The g ...

are produced via this process. A variant of wet spinning is dry-jet wet spinning, where the spinning solution passes through an air-gap prior to being submerged into the coagulation bath. This method is used in

Lyocell Lyocell, originally trademarked in 1982 as Tencel, is a form of regenerated cellulose. It consists of cellulose fibers, made by dissolving pulp and then reconstituting it by dry jet-wet spinning. The fiber is used to make textiles for clothing a ...

spinning of dissolved

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...

, and can lead to higher polymer orientation due to the higher stretchability of the spinning solution versus the precipitated fiber.

Gel spinning

Gel spinning, also known as semi-melt spinning, is used to obtain high strength or other special properties in the fibers. Instead of wet spinning, which relies on precipitation as the main mechanism for solidification, gel spinning relies on temperature-induced physical gelation as the primary method for solidification. The resulting gelled fiber is then swollen with the spinning solvent (similar to

gelatin dessert Gelatin desserts (also Jelly or Jello) are desserts made with a sweetened and flavoured processed collagen product (gelatin). This kind of dessert was first recorded as jelly by Hannah Glasse in her 18th-century book ''The Art of Cookery'', a ...

s) which keeps the polymer chains somewhat bound together, resisting relaxation which is prevalent in wet spinning. The high solvent retention allows for ultra-high drawing as with ultra high molecular weight polyethylene (UHMWPE) (e.g., Spectra^®) to produce fibers with a high degree of orientation, which increases fiber strength. The fibers are first cooled either with air or in a liquid bath to induce gelation, then the solvent is removed through ageing in a nonsolvent, or during the drawing stage. Some high strength

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including b ...

and

polyacrylonitrile Polyacrylonitrile (PAN), also known as polyvinyl cyanide and Creslan 61, is a synthetic, semicrystalline organic polymer resin, with the linear formula (C3H3N)n. Though it is thermoplastic, it does not melt under normal conditions. It degrades bef ...

fibers are produced via this process.

Electrospinning

Electrospinning uses an electrical charge to draw very fine (typically on the micro or nano scale) fibres from a liquid - either a polymer solution or a polymer melt. Electrospinning shares characteristics of both

electrospray The name electrospray is used for an apparatus that employs electricity to disperse a liquid or for the fine aerosol resulting from this process. High voltage is applied to a liquid supplied through an emitter (usually a glass or metallic capilla ...

ing and conventional solution dry spinningZiabicki, A. ''Fundamentals of fiber formation'', John Wiley and Sons, London, 1976, . of fibers. The process does not require the use of coagulation chemistry or high temperatures to produce solid threads from solution. This makes the process particularly suited to the production of fibers using large and complex molecules. Melt electrospinning is also practiced; this method ensures that no solvent can be carried over into the final product.Hutmacher DW & Dalton PD (2011) Melt Electrospinning. Chem Asian J, 6, 44-5.

Post-Spin Processes

Drawing

Finally, the fibers are drawn to increase strength and orientation. This may be done while the polymer is still solidifying or after it has completely cooled.

References

{{reflist Plastics industry Synthetic fibers