the physical structure of fiber
- 1. Textile Physics-1 MD LUTFUR RAHMAN
- 2. The Physical Structure of Fiber
- 3. Orientation: The alignment of the structural elements of a material. In polymer, orientation at different structural levels may be observed. Ex: polymer chains, segment of chains, crystallites etc. Amorphous polymer orientation : Polymers are oriented or aligned at random fashion in amorphous region, i.e. shows no particular order of arrangement. Crystalline polymer orientation : In crystalline regions the polymers are oriented or aligned longitudinally into more or less parallel order.
- 4. Properties of more amorphous fibers : -Formation of less effective inter-polymer forces of attraction. (weak) -Permits easier entry of water and dye molecules as well as molecules, ions and/or radicals of degrading agents. So more absorbent and more easily dyed . -Allows the polymers to be more readily displaced when the fiber is subjected to stresses and strains during wearing. -less durable -more easily degraded by chemicals -more pliable, softer handling Properties of more crystalline fibers : -Formation of more effective inter-polymer forces of attraction. -Restricts the entry of water and dye molecules as well as molecules, ions and/or radicals of degrading agents. So less absorbent and less easily dyed -Does not allow the polymers to be displaced when the fiber is subject to stresses and strains during wearing . -more durable -less easily degraded by chemicals -less pliable, stiffer handling
- 5. Requirements of fiber formation or fiber forming polymer 1)Hydrophilic: A fiber is comfortable to wear if its polymer system is made up of hydrophilic polymers, and the system allows the entry of water molecules. Hydrophobic polymer fibers whose polymers are non-polar are yet used as fibers for textile applications. In order to make the textile materials of these fibers more water attracting, absorbent and comfortable, hydrophobic- polymer fibers need to be blended with the hydrophilic polymer fibers to get desired properties. 2)Chemical resistant: Close packing of the polymers prevents ready entry of chemicals. More the polymer system is crystalline in nature more will be the resistance of the fibers against degradation by chemicals. Thus, many synthetic fibers are used in industry to make filter fabrics and protective clothing. Fiber polymers should be chemically resistant for a reasonable length of time against the common degrading agents such as sunlight and weather, common types of soiling, body exudations, laundry liquors and dry cleaning solvents. The most required property of chemically resistant polymers should be such that it should not be toxic or hazardous to wear against human skin. Polymer of fibers should be chemically resistant, but they should not be inert. Chemical inertness of fiber polymers results in detrimental effect on other fiber-forming requirements. The polymers of chloro-fibers, fluorocarbon, polyethylene and polypropylene may be regarded as chemically inert from a practical point of view.
- 6. 3)Linear: Fiber polymer should be linear i.e. the polymers should not be branched. Highly linear polymers will form more crystalline regions, which results in a large number of inter-polymer forces of attraction within the polymer system. 4)Capable of being oriented: Fiber polymers should be capable of being oriented. The polymers are aligned into more or less parallel order in the direction of the longitudinal axis of the fiber or filament. The orientation of polymers in the polymer system of any fiber consists of two forms. The two forms of polymer orientation are: • amorphous regions (random) • crystalline regions (highly ordered, highly oriented)
- 7. 5)Long: Fiber polymers should be long. The length of polymers is directly related to the strength of fiber by holding the crystalline regions together. To produce a fiber with adequate strength, a polymer length of 100 nanometers is required. Polymers of such length can be oriented easily. The orientation of polymers give rise to sufficiently effective inter-polymer forces of attraction to form a cohesive polymer system and, hence, a useful fiber. The longer the polymers the more cohesive will be the polymer system and the stronger will be the fiber. For this to occur the polymers have to be aligned or well oriented so that the maximum formation of inter-polymer forces can take place.
- 8. 6)Able to form high melting point polymer systems: The fibers must have high melting point to withstand the most extreme heat conditions. Melting point of fiber needs to be above 225° C if it is to be useful for textile manufacture and apparel use. The longer the polymers and the better their orientation, the more inter-polymer forces of attraction will be formed, giving a more cohesive polymer system with a higher melting point. More heat or kinetic energy will be required to break the inter-polymer forces of attraction and free the polymers from each other.
- 9. Crystallinity and Amorphous The structure of a polymer is defined in terms of crystallinity. It is the degree of order or regularity in how the molecules are packed together. A well-ordered polymer is considered crystalline. Amorphous is the opposite to crystallinity.