Function of polybutadiene in the rubber modified polyblends

Polybutadiene based polyblends (Table 3.19) are very important plastics with industrial applications, e.g. impact resistance polymers and impact modifiers for rigid poly(vinyl chloride). These polyblends are very susceptible to photo-oxidative degradation, because of the presence of polybutadiene. Intensive studies of the photo-oxidation of the rubber modified polyblends lead to the following conclusions [761-764, 1936]  

The polybutadiene segment is the initial point of attack of oxygen, giving rise to allylic hydroperoxides. 

Photolysis of hydroperoxides leads to crosslinking of the polybutadiene component by addition of alkoxy radicals to 1,2-polybutadiene groups and conjugated carbonyl formed by alkoxy radical breakdown. 

Crosslinking destroys the elastomeric properties of the rubber phase with the loss of impact resistance of the polymer. 

Thermal processing activates polybutadiene modified polymers to photooxidation by introducing photosensitizing hydroperoxides into the polymer. 

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