HYBRID INJECTION MOULDING: OVERMOULDING OF METAL INSERTS WITH PP

Hybrid injection moulding (HIM) is an advanced injection moulding technology that uses dissimilar materials to produce complex parts. In this work, pretreated metal inserts were overmoulded with semicrystalline polypropylene. The effect of the injection moulding conditions and inserts temperature and roughness on the adhesion of both materials was studied. The effect of a simplified flame treatment on the metal surface modification and wettability was characterized using microscopy analysis and contact angle measurements. The crystalline structure of the overmoulded polymer was also evaluated by microscopy analysis. For the adhesion assessments, single lap shear tests were conducted at room temperature to measure the shear stress at the interfaces. It is shown that the temperature of the insert is one of the main variables affecting adhesion, even more then insert roughness and flame treatment.