Interestingly, the aging coefficient of NR with GM-ME-IPDI is little lower than that of NR with GM-ME when the aging time is less than 48 h, but the result is opposite when the aging time reaches 96 h. Moreover, with the increase of aging time, the difference of antioxidative ability of GM-ME and GM-ME-IPDI increases. The possible reason may be the smaller physical loss (resulting from migration during aging) of GM-ME-IPDI due to its higher molecular weight .