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CompanyLOGOSpecial FibersIng. Imtiaz Ahmed Khan, KOD,TUL.

ContentsSPECIAL FIBERS1Introduction2Polymers3Aramid Fiber4Properties of Aramid Fibers5ConclusionIng. Imtiaz Ahmed Khan, KOD,TUL.

IntroductionSpecial Fibers A walk down the memory laneIng. Imtiaz Ahmed Khan, KOD,TUL.

Define Fiber????????IntroductionIng. Imtiaz Ahmed Khan, KOD,TUL.

DEFINITION OF FIBERIntroduction A generic term for various types of matter thatform the basic elements of textile fabrics and othertextile structures. The Textile Institute (Denton and Daniels, 2002)more specifically define fiber: textile raw material,generally characterized by flexibility, fineness andhigh ratio of length to thickness.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Basic Characteristics of FiberIntroduction Fiber thickness is about three order less thanlength. Fiber thickness (dia): d=10 -610 -4 m Fiber length: l =10 -2 10 -1 m Ratio: l / d = 10 3Ing. Imtiaz Ahmed Khan, KOD,TUL.

What are Special Fibers…. Faster, stronger, lighter, safer ... these demandsare constantly being pushed upon today'sresearchers and manufacturers. High performance fibers or Special fibers aregenerally characterized by remarkably high tensilestrength and modulus as well as resistance to heat,flame, and chemical agents that normally degradeconventional fibers. Selection of suitable polymers gives fibers withhigh chemical or thermal resistance for particularapplications.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Polymers The word Polymer comes from the Greek ”poly”meaning many, and ”meros”, parts or units. Apolymer is a group of many units. You combinemany monomers (one unit) to create a polymer.So they are having repeating chemical units.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Polymers we'll talk about here are linear polymers.A linear polymer is made up of one molecule afteranother, hooked together in a long chain. Thischain is called the backbone. (Suitable for fibersnumbers of units > 80) A BRANCHED polymer chain has extra beginnings(branches!) along the chain and so it has lots ofends.(Not suitable for fibers)Ing. Imtiaz Ahmed Khan, KOD,TUL.

Remember that polymers are very long chains.These long chains:can bend and twist and get all tangled upalso can stick to each other. In backbone chains atoms are bonded by strongC – C covalent bond that requires high energy todisintegrate. (Approx 347 KJ/mol)Ing. Imtiaz Ahmed Khan, KOD,TUL.

In addition to the bonds which hold monomerstogether in a polymer chain, many polymers formbonds between neighboring chains. These are cohesive forces. Though not as strong or rigid as the bonds withinthe chain, these cross-links have an importanteffect on the polymer. The main cohesive forces activated are due tohydrogen bond and Van der Waals forces.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Polymer MorphologySpecial Fibers Molecular shape and the way molecules are arranged in asolid are important factors in determining the properties ofpolymers. From polymers that crumble to the touch to those used inbullet proof vests, the molecular structure, conformation andorientation of the polymers can have a major effect on themacroscopic properties of the material. Polymer molecules are so large, they generally pack togetherin a non-uniform fashion, with ordered or crystalline-likeregions mixed together with disordered or amorphousdomains. In some cases the entire solid may be amorphous,composed entirely of coiled and tangled macromolecularchains. Crystallinity occurs when linear polymer chains arestructurally oriented in a uniform three-dimensional matrix.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Increased crystallinity is associated with anincrease in rigidity, tensile strength and opacity(due to light scattering). Amorphous polymers areusually less rigid, weaker and more easilydeformed. They are often transparent. On heating or cooling most polymers undergothermal transitions that provide insight into theirmorphology. These are defined as the melttransition, Tm , and the glass transition, Tg .Ing. Imtiaz Ahmed Khan, KOD,TUL.

Tm is the temperature at which crystalline domainslose their structure, or melt. As crystallinityincreases, so does Tm. Tg is the temperature below which amorphousdomains lose the structural mobility of the polymerchains and become rigid like glass. In the crystallization process, it has been observedthat relatively short chains organize themselvesinto crystalline structures more readily than longermolecules. Therefore, the degree of polymerization(DP) is an important factor in determining thecrystallinity of a polymer.Ing. Imtiaz Ahmed Khan, KOD,TUL.

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Applications of Special Fibers Applications include uses in the aerospace,biomedical, civil engineering, construction,protective apparel, geotextiles, and electronicareas.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Applications Contd… For many years, plastics reinforced with polymerfibers have been utilized in the manufacture ofboats and sports cars. More recently, ultrahighstrength, high modulus fibers have been inventedand combined into composites whose strength andstiffness on a specific basis are unmatched byconventional construction materials. Compositesare now replacing metals in such crucialapplications as aircraft and the space shuttle. Thepolymeric composites contain carbon or aramidfibers several times stiffer, lesser weight, thansteel. In composite materials the fibers support theload that is distributed by the plastic that alsoprevents fatigue and failure.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Utilization of fibers in different fieldsSpecial FibersIng. Imtiaz Ahmed Khan, KOD,TUL.

Strength of Special FibersSpecial FibersIng. Imtiaz Ahmed Khan, KOD,TUL.

www.themegallery.comTable of Fiber Properties

Special fibers I will be discussing Aramid fibers in todays lecture.Ing. Imtiaz Ahmed Khan, KOD,TUL.

ARAMIDSwww.themegallery.comPolymer Preparation: Basic SynthesisAromatic polyamides: A manufactured fiber in whichfiber forming substance is a long chain syntheticpolyamide in which at least 85 % of the amides(-CO-NH-) linkage are attached directly to twoaromatic rings. Generic reaction Amine Group + Carboxylic Acid Halide Group nNH2-Ar-COCl-[NH-AR-CO]n-+ nHCLIng. Imtiaz Ahmed Khan, KOD,TUL.

AramidsPolymerization ProcessIt is a low temperature polymerization. Factorsaffecting polymer characteristics are: Solubility – concentration – temperaturerelationships, which makes the choice of solventcritical; Salt concentration at constant polymerconcentration, which partly governs the degree ofpolymerization and polymer inherent viscosity.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Aramids SynthesisNH 2NH 2 + ClCO ClCOPPDTCLIng. Imtiaz Ahmed Khan, KOD,TUL.

Types of Aramids Aramid fibers are novel high-tech materials thathave revolutionized our lives with their numeroususes. The fibers can be classified according to thepositions of the linkage such as Para, Meta andheterocyclic. They were initially developed and continue todevelop in these three directions. Para-aramidfibers are in the form of high-strength highmodulusyarns for fabrication of high-strength andlight composite materials.Ing. Imtiaz Ahmed Khan, KOD,TUL.

Meta-aramid fibers are of wide textile and, inparticular, technical use, which are primarily usedto protect humans from high temperatures andfire. Heterocyclic aramid fibers give unmatchedperformance strength and fatigue resistance.Several more configurations are possible butcommercially it only few are feasible to beproduced commerciallyIng. Imtiaz Ahmed Khan, KOD,TUL.

Nomex StructureRibbon like structureIng. Imtiaz Ahmed Khan, KOD,TUL.

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Aramid Fiber Properties These aromatic rings and amide linkages ensure itshigh thermal stability and strength of aramidfibers. Bond dissociation energies of C ─ C and C ─ Nbonds in aromatic polyamides are ~20% higherthan those in aliphatic polyamides. This is thereason why the decomposition temperature ofNomex® exceeds 450oC . Nomex® has a triclinic unit cell and is significantlyless crystalline than KevlarIng. Imtiaz Ahmed Khan, KOD,TUL.

Properties Contd…Ing. Imtiaz Ahmed Khan, KOD,TUL.

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ConclusionSpecial fibers these high performance fibers showed a stepchange in strength and stiffness. They are highmodulus,high-tenacity (HM-HT) fibers. Excellent use in Various fields and industry. A new era of fibers. Assignment‘Though not as strong or rigid as the bonds within thechain, these cross-links have an important effect onthe polymer.’In no more than 1000 words explain theefffect of these cross linkings on polymer properties.Company Logo

CompanyLOGOIng. Imtiaz Ahmed Khan, KOD,TUL.imtiaz.ahmed.khan@tul.cz