A composition is composed of (A) an ethylene/alpha-olefin/diene TEMPO compound having the Structure (I) and (D) a peroxide. The molar ratio of isocyanate groups of Component (B) to the functional groups of Component (C) is from 0.80 to 1.10. A composition is composed of (A) an ethylene/alpha-olefin/diene interpolymer; a second composition comprising a reaction mixture comprising (B) an isocyanate comprising at least two isocyanate groups and (C) a TEMPO compound having the Structure (I) and (D) a peroxide, wherein the molar ratio of isocyanate groups of Component (B) to the functional groups of Component (C) is from 0.80 to 1.10. In Structure I, R1, R2, R3 and R4 are each independently selected from H and C1-C6 alkyl groups and X is a functional group selected from OH and NH2.