Chemiluminescence from poly(styrene- b-ethylene- co-butylene- b-styrene) (SEBS) block copolymers

A detailed analysis of the chemiluminescence emission (CL) from poly(styrene- b-ethylene- co-butylene- b-styrene), SEBS, was carried out. A phenol–phosphite stabilization system based on Irgafos 168 and Irganox 1330, was studied. The kinetic analysis of the CL profile under nitrogen shows a first-order reaction for the decay of chemiluminescence. The activation energy shows different values as a function of temperature, showing that different reactions are involved in the thermal degradation of the SEBS. The CL decay rate correlates well with the amount of the phosphite, Irgafos 168, and confirms the activity of this stabilizer as radical chain-breaking antioxidant in these copolymers. The isothermal analysis of CL under oxygen allows evaluation of the oxidation state, as well as the efficiency of the antioxidants. Good correlations are found between the CL parameters and concentration of Irgafos 168. Several factors suggest that oxidation begins in the interfacial region. Spectral analysis of the chemiluminescence shows the presence of different types of hydroperoxides. Finally, the characterization of the SEBS copolymers by differential scanning calorimetry reveals an order–disorder transition, assigned to aggregates that behave as paracrystalline regions.