Change in the chemical and/or physical structure of the polymer chain.
Degradation is undesirable during use but desirable after use (as in biodegradation).
Types of Degradations
| Type of degradation | Agent |
|---|---|
| Thermal degradation | Heat |
| Chemical degradation | Chemical |
| Photo-degradation | UV & other radiations |
| Mechanical degradation | Stress |
| Biodegradation | Bacteria and other organisms |
Susceptibility to Degradation
Depends on its structure and the type of degradation.
- Chains containing aromatic functionality are suspectible to ultraviolet degradation
- Hydrocarbon-based polymers are susceptible to thermal degradation
Bond Rupture or Scission
Breaking into smaller polymer chains. Molecular weight of the polymer decreases.
Swelling & Dissolution
Main form of degradation when a polymer is exposed to liquids.
Swelling
The liquid or solute diffuses into the polymer. Polymer absorbs the liquid or solute. Chain separation increases. Secondary inter-molecular bonding forces decreases.
Dissolution
Extreme state of swelling. Occurs when the polymer is completely soluable.