Carbonyl groups polybutadiene

In the free radical oxidation of polybutadienes, both the peroxides and carbonyl groups are formed typically. Consequently, the presence or absence of carbonyl groups in the reaction products of the photooxidation of polydiene may be an indication of the oxidation mechanism. 

ABS is sensitive to oxidation due to the presence of polybutadiene components, which act as oxidation sensitisers and lead to the formation of carbonyl groups, which absorb at 1,680-1,750 cm" [29]. 

During UV irradiation in air (oxygen) the absorption spectrum of styrene-butadiene rubbers (SBR) (Fig. 3.59) changes rapidly, in a way similar to that of polybutadiene (cf Fig. 3.58). This change is caused by carbonyl groups aliphatic (<300nm), aromatic or a,/ -unsaturated ketones and aldehydes (>300nm)p93]. 

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. 

---