Degradation means uncontrolled
reduction of molecular weight. It also means the rupture of chemical bond. And
for this degradation the polymer looses its luster and stability.
Physical degradation:
- Thermal degradation.
- Mechanical degradation.
- By ultrasonic waves degradation.
- Photo degradation.
- By light energy radiation.
Thermal degradation: It may be
affected the groups joined to C-C bonds the aromatic branching and the presence
of oxygen atom in the polymer chain which causes polymers to thermal
degradation.
Mechanical degradation:
- When a polymer dissolved in a solvent and subjected to vigorous stirring or beating and undergoes consideration molecular degradation.
- In the rubber industry rubber is masticated by passing it through two rotating rollers to reduce its molecular weight the mastication converts hard and tough rubber into a soft, supple.
- The larger the initial molecular weight, the greater the molecular weight drop due to mechanical degradation.
Photo degradation:
- Free radicals are formed during photo-degradation and the reaction of free radicals depends on the physical state of polymer.
- Photo stabilizer protects polymers from the deteriorating effect of light. The function of photo stabilizer is to absorb the ultra violate radiation.
Light radiation: X-ray, gamma
rays, alpha and beta rays are among the well known high energy radiation.
Types of Degradation: Degradation are two types. They are:
a. Chain-end degradation.
b. Random degradation.
Types of Degradation: Degradation are two types. They are:
a. Chain-end degradation.
b. Random degradation.
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