Photostabilization of ethylene-propylene-ethylidenenorbornene terpolymer by hindered amine compounds

The effect of bis(2,2,6,6-tetramethylpiperidinyl)sebacate (NH) and the stable bisnitroxyl radical (NO^·) arising from it, on the 9,10-diphenylanthracene (DPA) sensitized photo-oxidation of ethylene-propylene-ethylidenenorbornene terpolymer (EPNB) has been examined. It was found that the formation of hydroperoxide, which is a result of the photo-oxidation of EPNB, is inhibited by both compounds. The stabilizing action of the bisnitroxyl radical is considerably greater, however. The radical NO^· was found to be able to quench the singlet excited state of DPA. Both the compounds quench singlet oxygen, but the effectiveness of NO^· is greater. The radical NO^·, in its electronically excited state, induces hydroperoxide decomposition. The hydroxylamine formed in this process can participate in the inhibition of polymer photo-oxidation.