Nitrile-butadiene rubber/poly(propylene carbonate) (NBR-PPC) elastomer was studied as a coupling agent of the blends of poly(vinyl chloride) (PVC) with poly(propylene carbonate) (PPC). It greatly improved the PVC/PPC system mechanical properties that were dependent on the amount and composition of the coupling agent. When the coupling agent consisted of a 70/30 ratio of NBR/PPC (in which NBR had 34% nitrile content) and 2.5 phr of benzoyl peroxide (BPO) initiator and underwent a prevulcanization, the blends of PVC/PPC displayed excellent mechanical properties by adding 8 phr of the coupling agent.