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FIBER FORMATION AND MORPHOLOGYFiber morphology refers to theform and structure of a fiber,including the moleculararrangement of individualmolecules and groups ofmolecules within the fiber.
Most fibers are organic materialsderived from carbon combinedwith other atoms such as oxygen,nitrogen, and halogens.The basic building blocks thatorganic materials form ascovalently-bonded organiccompounds are called monomers
Monomers react or condense toform long-chain molecules calledpolymers made up of a givennumber (n) of monomer unitswhich are the basic building unitof fibers.
Fiber Spinning. There are several methods usedto spin a fiber from its polymer,including melt, dry, wet, emulsion,and suspension spinning.Melt spinning
Melt spinningThe polymer from which thefiber is made is melted and thenforced through a spinneret andinto air to cause solidificationand fiber formation.
Dry and wet spinningprocesses involve dissolving the fiber-forming polymer in an appropriate solvent,followed by passing a concentrated solution(20%-50% polymer) through the spinneretand into dry air to evaporate the solvent inthe case of dry spinningor into a coagulating bath to causeprecipitation or regeneration of the polymerin fiber form in the case of wet spinning.
Emulsion spinningused only for those fiber-forming polymersthat are insoluble. Polymer is mixed with asurface-active agent (detergent) andpossibly a solvent and then mixed at highspeeds with water to form an emulsion ofthe polymer. The polymer is passed throughthe spinneret and into a coagulating bath toform the fiber.
The spinning process can bedivided into three steps:(1) Flow of spinning fluid within and throughthe spinneret under high stress and sheer.(2) Exit of fluid from the spinneret with reliefof stress and an increase in volume(ballooning of flow).(3) Elongation of the fluid jet as it issubjected to tensile force as it cools andsolidifies with orientation of molecularstructure within the fiber.
Thermoplastic man-made fibers can bepermanently heat set after drawing andorientation. The fiber will possess structuralintegrity and will not shrink up to that settingtemperature. Also, thermoplastic fibers or yarnsfrom these fibers can be texturized to give three-dimensional loft and bulkiness:1. Through fiber deformation and setting ator near their softening temperature.2. Through air entanglement.3. Through differential setting within fibersor yarns
Staple FormationContinuous filaments can be cutinto staple by wet or dry cuttingtechniques. In wet cutting, thewet-spun fiber is cut to uniformlengths right after spinning, whiledry cutting involves partialcutting, debonding, and shufflingof the dry tow to form a sliver.
STRUCTURE-PROPERTY RELATIONSHIPSThe basic chemical and morphological structureof polymers in a fiber determines the fundamentalproperties of a fabric made from that fiber.Although physical and chemical treatments andchanges in yarn and fabric formation parameterscan alter the fabric properties to some degree,the basic properties of the fabric result fromphysical and chemical properties inherent to thestructure of the polymer making up the fiber.