Provided herein is a process for making a grafted cross-linked polymer blend, by polymerizing a first and second polymer solution (each having 75 to 99 wt % propylene-derived units, 1 to 25 wt % ethylene-derived units, and 0.05 to 6 wt % diene-derived units); combining the first and second polymer solution to produce a polymer blend solution; removing solvent from the polymer blend solution to produce a polymer blend; mixing the polymer blend with a coagent and a vinyl-terminated silane compound; subjecting the polymer blend to electron beam irradiation to grafting the vinyl-terminated silane compound to either or both of the first polymer and the second polymer to form a grafted polymer blend; and moisture curing the grafted polymer blend to form a grafted cross-linked polymer blend, wherein the grafted cross-linked polymer blend is substantially free of peroxide.