Adhesion control for injection overmolding of polypropylene with elastomeric ethylene copolymers

Abstract

Two types of random semicrystalline copolymers (ethylene–octene and ethylene–butene) were overmolded on a core polypropylene. Maximum solid–liquid interface temperature achieved for the overmolding injection process is used as the key parameter for adhesion control. The main bonding process is shown to be a Rouse-type fingering mechanism that develops in short time scales. Normalized peel tests were conducted on overmolded samples to measure the resulting polypropylene copolymers' bonding strength. All the ethylene random copolymers used for this study give good adhesion to polypropylene in overmolding processes, provided the right range of interface temperature is reached. Adhesion strength can be easily controlled for efficient debonding and recycling of used overmolded parts