Tuesday, 20 October 2009

A Few Notes About Fiber Chemistry



1. All fibers are formed from polymers, are not the only products containing polymers

2. Polymer means many units. Each individual molecule is known as monomer and the process of joining all the monomers together to form long chain molecules (polymers) is known as polymerisation.

3. The degree of polymerisation is the number of monomers units in the polymer. These may be of same type ( a homopolymer ) or two different randomly arranged monomers ( a copolymer)

4. There are two types of polymerisation: addition polymerisation, where all the atoms present in the monomers are also present in the polymer and condensation polymerisation where some small molecules are eliminated during polymerisation.

5. Polypropylene and acrylic polymers are produced by addition polymerisation.

6. Polyester, polyamide, wool, silk, cotton, flax, jute and viscose polymers are produced by condensation polymerisation.

7 There are three types of intermolecular forces. In decending order of strength: they are hydrogen bonds, polar bonds and Van der Waal's forces.

8. The properties of polymers for good fiber formation are: high degree of polymerisation, good intermolecular forces, linear and regular arrangement of monomers, high orientation of molecules and an inflexible repeat unit.

9. Crystalline regions are highly ordered areas within the fibers. They give the fiber its tensile and rigidity properties.

10. Amorphous regions are where the molecules are not closely packed within the fibers. They give the fiber its flexibility, extensibility and elasticity.

11. In natural fibers, crystalline regions develop as the fiber grows. In MMF, the ratio of crystalline to amorphous regions can be altered by drawing and heat setting.

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