AbstractEthylene copolymer resin (ECR) modifiers, designed to be soluble in all proportions in PVC, form a wide variety of plasticized PVC blends. These solid, high molecular weight (Mw>250,000) resin modifiers, unlike conventional liquid plasticizer, exhibit outstanding permanence in PVC. Compounding procedures, used for liquid plasticized PVC, are sometimes inadequate to produce homogeneous blends of PVC/ECR. A number of effective melt compounding techniques and a new family of ECR modifiers have been developed to produce homogeneous blends exhibiting many outstanding properties, including fluids/chemical resistance, high/low‐temperature service, and weatherabilit