Degradation and Degrading Agents

DEGRADATION OF TEXTILE FIBRE

Concept of degradation

Polymer degradation involving light and heat is defined as a combination of chemical and physical changes occurring during the processing, storage and usage. This results in the loss of some useful properties of the polymeric material. These changes are mainly due to the competing chemical processes of macromolecular degradation and cross-linking. Polymer degradation and cross-linking involve a variety of conjugated chain-radical, ionic and molecular reactions.

The degradation reaction is broadly of two types: (1) Chain-end degradation and (2) random degradation. In the first type, the degradation starts from the chain-ends, resulting in a successive release of the monomeric units. This type of degradation is also called depolymerization (unzipping), the reverse of the propagation step in chain polymerization. The second type of degradation occurs at any random point along the polymer chain is called random degradation (zipping) which is the reverse of the polycondensation process. A distinguishing characteristic between the two types of degradation is that generally in the random process the molecular weight falls rapidly but considerably more slowly than in depolymerization.


Degrading agents

Types of degradation in the presence of various influences

Degrading Agents Types of degradation
1.Light (UV, visible) 1. Photochemical degradation

2. X-ray, gama-ray, fast electrous etc. 2. High energy radiation induced
degradation.
3. Laser light 3. Ablative photo degradation
4. Electrical field 4. Electrical Aging.
5. Plasma 5. corrosive degradation, etching.
6. Microorganism 6. Bio degradation.
7. Enzymes 7. Bio crosion.

8. Stress forces 8. Mechanical degradation
9. Ultra sound 9. Ultrasonic degradation
10. Chemicals (Acid, base etc.) 10. Chemical degradation
11. Heat 11. Thermal degradation and/or
decomposition
12. Oxygen, Ozone 12. Oxidative degradation (oxidation),
ozonolysis
13. Heat and oxygen 13. Thermoxidative degradation and/or
decomposition combustion
14. Light and O2 14. Photo oxidation