Define Nylon-6,6 | Properties of Nylon 6,6 Fiber | Manufacturing Process of Nylon 6,6

Nylon-6,6 Fiber:
Nylon-6,6 (PA66) is semicrystalline polyamide commonly used in fiber applications such as carpeting, clothing, and tire cord. It is also used as an engineering material in bearings and gears due to its good abrasion resistance and self-lubricating properties.
Structure of Nylon 6,6
Properties of Nylon 6,6:
  • Glass transition temperature: 50oC.
  • Melting temperature: 255oC.
  • Amorphous density at 25oC: 1.07 g/cm3.
  • Crystalline density at 25oC: 1.24 g/cm3.
  • Molecular weight of repeat unit: 226.32 g/mol.
Manufacturing Process of Nylon 6,6:
  1. The manufacturing process starts with the production of two chemicals hexamethylene diamine and adipic acid both of which contains 6carbon atoms from coal.  
  2. These chemicals are combined to form the nylon salt, which is dissolved in water and sent to the spinning mill. 
  3. The nylon salt solution is made into a concentrated solution by heating in large evaporators.
  4. The concentrated solution is then heated in an autoclave under the pressure and temperature. The polymerization takes place combining the two chemicals into polymers which are like a giant chains. The molten polymer is processed in a manner similar to nylon 6
Manufacturing Process of Nylon 6,6
The filaments obtained from spinning are stretched by drawing process. The drawing process is accomplished in two stages:
  1. Unwinding the yarn from one godet, or wheel, winding it onto another godet that is rotating much faster. The speed of the second wheel determines the amount of cold-drawing or stretching.
  2. The yarn from the second godet is wrapped on a cylindrical tube called a pirn. The filaments can be stretched from 2 to 7 times their original length. The molecules in the filament structure straighten out, become parallelized, and are brought very close together.


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