TT 2255 STRUCTURE AND PROPERTIES OF FIBRES |
STRUCTURE OF FIBRES |
Basic requirements for fibre formation. Structure of natural and man-made textile fibres – chemical structure, fine structure, and morphological structure of cotton, viscose, acetate, polyester, polyamide, polyacrylonytrile, polyethylene, polypropylene and bast fibres. Basic concepts of intra- and inter-molecular forces, degree of order, degree of orientation of molecular chains, ordered and disordered regions. Models of fibre structure – fringed micelle model, modified-fringed micelle model, fringed fibril model. Similarities and differences amongst the structural features of natural and man-made fibres. Investigation of fibre structure – Electron microscopy, X-ray diffraction methods, Infra-red radiation techniques, density measurement.
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MOISTURE ABSORPTION PROPERTIES OF FIBRES |
Definitions of humidity – absolute humidity and relative humidity, moisture content and regain. Hygroscopic nature of fibres – regain curves. Measurement of regain and determination of correct invoice mass in fibres. Hysteresis in moisture absorption. Equilibrium absorption of moisture by fibres. Effect of fibre structure – hydrophilic groups and non-crystalline regions on moisture absorption. Effect of ambient conditions – relative humidity and temperature on regain of fibres. Heats of sorption – differential and integral - relation with fibre structure and regain, measurement of heat of wetting. Conditioning of fibres – mechanism of conditioning, factors influencing rate of conditioning, effect of conditioning on fibre properties. Swelling of fibres – axial swelling, transverse swelling, area swelling and volume swelling. |
MECHANICAL PROPERTIES OF FIBRES |
Tensile testing of fibres – cotton, viscose, acetate, modal, lyocel, polyester, polyamide, polyacrylonytrile, polyethylene, polypropylene, jute and flax fibres Definitions of terms – load, elongation, breaking strength, breaking extension, tensile stress, tensile strain, mass specific stress, yield point, initial modulus, work of rupture and work factor. Stress-strain curves for various textile fibres and their significance. Influence of fibre structure, humidity and temperature on stress-strain characteristics of fibres. Methods of tensile testing – constant rate of loading and constant rate of extension, differences between the two methods of test. Elastic properties – elasticity, elastic recovery and its relation to stress and strain, work recovery, typical values of elastic recovery and work recovery for various textile fibres. Mechanical conditioning of fibres – advantages. Time effects – stress relaxation and creep phenomena. Dynamic tensile testing of fibres. Torsional rigidity – its relation to other fibre properties, measurement techniques. Flexural rigidity – its relation to other fibre properties, measurement techniques. |
OPTICAL AND FRICTIONAL PROPERTIES |
Refractive index of fibres – definition, factors influencing and measurement. Birefringence – measurement techniques, effect of factors like fibre orientation, density and regain. Optical orientation factor, its relation with refractive index and birefringence. Reflection of light – specular and diffused reflection, lustre, lustre index, factors influencing lustre. Absorption of light – dichroism, dichroic ratio. Introduction to fibre friction. Theories of friction – Amonton’s law, Bowden’s adhesion shearing mechanism, Lincoln’s law. Measurement of friction – friction between single fibres, friction between fibre assemblies. Factors influencing fibre friction. Role of friction in fibre processing. Friction in wool – directional frictional effect, felting. |
ELECTRICAL AND THERMAL PROPERTIES |
Definition of electrical resistance, electrical resistance of fibres, measurement of resistance in fibres, factors influencing electrical resistance. Dielectric properties, factors influencing dielectricity. Static electricity – generation of static charge and measurement, problems encountered during processing, elimination techniques. Thermal properties – specific heat, thermal conductivity, thermal expansion and contraction, structural changes in fibres on heating, thermal transitions – glass transition and melting, heat setting. Flammability characteristics of fibres. |
REFERENCE |
Text Books |
1. Morton W.E and Hearle, J.W.S., “Physical Properties of Textile Fibres”, The Textile Institute, Manchester, U.K., 1993.
2. Meredith. R and Hearle, J.W.S., “Physical Methods of Investigation of Textiles”, Wiley Publication, New York, 1989. |
Reference Books |
1. Gupta V.B. Textile Fibres: Developments and Innovations. Vol. 2, Progress in Textiles: Science & Technology. Edited by V.K. Kothari, IAFL Publications, 2000.
2. Meredith R., “Mechanical Properties of Textile Fibres”, North Holland, Amsterdam 1986.
3. Murthy, H.V. S., Introduction to Textile Fibres, The Textile Association, India, 1987.
4. Mishra, S.P., Fibre Science & Technology, New Age International Publishers, 2000. |
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