Termal Properties of Textile Fibers

Termal Properties of Textile Fibers:
The property which is shown by a textile fiber when it is subjected to heating is called thermal property.  

Thermal properties are including:
  1. Thermal conductivity
  2. Heat of wetting or heat of absorption
  3. Glass transition temperature
  4. Melting temperature
  5. Heat setting
  6. Thermal expansion
Thermal conductivity: 
Thermal conductivity is the rate of heat transfer in degree along the body of a textile fiber by conduction. Higher the thermal conductivity indicates the fiber more conductive. Thermal conductivity is measure by co-efficient of thermal conductivity. 

Heat of wetting: 
When a textile fiber absorb moisture or water it gives of some amount of heat which is called heat of wetting or heat of absorption. Heat of absorption resulting from changes in moisture regain rather than the thermal conductivity. If 1gm of dried textile fiber is completely wetted then heat in calory/gm is involved which is known as heat of wetting for that fiber. 

Glass transition temperature(Tg): 
The temperature up to which a fiber behaves hard as like glass and after which it behaves soft as like rubber is called Glass transition temperature and it is denoted by Tg. The range of Tg is lies between -100˚C to 300˚C 

Melting temperature: 
A temperature at which fiber melt completely is called melting temperature. At melting temperature fiber losse its identity and convert it into a viscous liquid. At melting temperature fiber also losse its strength and some molecular weight. 

Thermal expansion: 
Thermal expansion can be measured by co-efficient of thermal expansion and which is defined as the fractional increase in length of a specimen to rise in temperature by 1˚C. Co-efficient of thermal expansion ═ Length increased / initial length of specimen ═ ∆L / L ═ L2-L1 / L1 

Heat setting: 
Heat setting is the process of stabilizing the form of fibers, yarns, fabric or garment by means of successive heating or cooling in dry and wet condition.

Static Electricity
If two surfaces come in close contact with each other, then charge is created due to friction between them. The produced charge remains enclosed and static in those surfaced. They can not move from one place to another place. Here only charges are exchanged between two surfaces. This type of electricity is called static electricity.

Problem caused by static electricity in textile:

1. Similar charge repel each other:
  • The filament in a charged warp will blow out away from one another.
  • This causes difficulties in handling materials.
  • There will be ballooning of a bundle of sliver.
  • Cloth will not fold down neatly upon itself when it comes off a finishing machine.
2. Different charge attracts each other:
  • Difficulties in the opening of the parachute.
  • Different parts of garments may be stick together.
3. Attraction between charged particles & charged textile materials:
  • Roller lapping may occur.
  • Dust, Dirt’s etc may be attracted by the textile material as a result materials become dirt.
  • Soiling of cloth may occur.
  • Fibers may stick to the earthed parts of the machine.
Methods of minimizing static electricity: 
  1. By using conducting liquids like emulsion, oil, friction between the materials ca be reduced as a result, static electricity will be minimize. 
  2. By increasing relative humidity of the atmosphere, static electricity can be minimized.
  3. By using anti-static agent on the materials static problem may reduce.
  4. By ear thing the metallic part of the machinery static electricity can be minimized. By blending conductive materials with non conductive materials, static electricity can be minimized.
Fiber migration:
Migration occurs during spinning both in staple and filament yarns. The effect of migration is more pronounced in staple yarn than in filament yarn. The migration of fiber affect on many properties of fiber as like elongation and strength. According to the textile institute “The change in the distance of a fiber or filament form the axis of a yarn during production is called fiber migration.

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