Study of the adhesion strength on overmoulded plastic materials using the essential work of interfacial fracture (EWIF) concept

The influence of the overmoulding processing conditions (melt and mould temperatures, holding pressure and injection rate) on the adhesion strength between two polymers in a hard–soft part was studied. The used materials were thermoplastic vulcanized elastomer (TPV) and polypropylene (PP). The study of the adhesion strength was made by measuring the essential work of interfacial fracture (EWIF) concept using a single edge-notched tension (SENT) geometry. It was observed that, the data distribution was good since an adequate correlation between the total work of interfacial fracture and the ligament length was obtained. It was verified that, when the melt temperature, and in some cases, the mould temperature are increased, a higher adhesion strength is obtained. These parameters affect in higher degree the adhesion strength, since they may improve the interdiffusion and the wetting process of the PP substrate by the molten material (TPV), causing as a result a good contact between them. A little influence was observed in the case of the holding pressure and injection rate.