Thermo-oxidation and degradation of polymers

Thermo-oxidation and degradation of polymers

• Thermo-oxidation and degradation of polymers

• Jozef Rychlý Polymer Institute Dúbravská cesta 9, 843 42 Bratislava, Slovak Republic

Chemical degradation is accompanied by the reduction of the molar mass, increase of the molar mass due to crosslinking, or it occurs as polymer analogous reaction typical by unzipping of side groups of the macromolecular chain. Degradation (physical) may involve also the physical processes like recrystallisation, denaturation (proteins). Ageing, (corrosion) is related to the long term degradation due to weathering and involves both.

• Chemical degradation is accompanied by the reduction of the molar mass, increase of the molar mass due to crosslinking, or it occurs as polymer analogous reaction typical by unzipping of side groups of the macromolecular chain. Degradation (physical) may involve also the physical processes like recrystallisation, denaturation (proteins). Ageing, (corrosion) is related to the long term degradation due to weathering and involves both.

Polymers are organic and inorganic materials composed of structural units – mers – kept together by chemical bonds.

• Polymers are organic and inorganic materials composed of structural units – mers – kept together by chemical bonds.

• Their stability properties are detemined by long entangled chains and by free volume. Small change such as disruption of the chain may change the properties significantly.

• Loss of properties due the change in position of macromolecular chains and additives in the volume without necessary chemical change.

Oxidation stability tests follow from Bolland Gee scheme:

• Oxidation stability tests follow from Bolland Gee scheme:

• Time or temperature evolution of concentration of hydroperoxides, DSC, thermogravimetry, chemiluminiscence, analytical determination of carbonyls, mechanical properties changes, etc.

• daylight (0-15 days), 1000 Wm-2, 25°C/50% RH

Polyester urethane are hydrolytically less stable than polyether urethane while polyether urethanes are less stable towards light induced degradation.

• Polyester urethane are hydrolytically less stable than polyether urethane while polyether urethanes are less stable towards light induced degradation.

Degradation is inevitable symptom of the polymer service life. It can be slowed down, with much more pronounced induction time, but it cannot be avoided.

• Degradation is inevitable symptom of the polymer service life. It can be slowed down, with much more pronounced induction time, but it cannot be avoided.

• The detailed knowledge on the kinetics is always necessary!