Degradation of Polymers

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

Note

UV stablized - the polymer is protected from UV degradation.

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.