Hard/soft combinations based on thermoplastic elastomer and a rigid thermoplastic polymer: Study of the adhesion strength

Abstract The objective of this work was to compare different test methods for determining the adhesion strength between a two overmolding materials: thermoplastic vulcanized elastomer (TPV) and a polypropylene (PP). The TPV/PP system was overmolded using different melt temperatures. Three testing methods were studied: Tensile test, Peeling test, and Essential Work of Interfacial Fracture (EWIF) at three different geometries: Single (SENT), Double (DENT) and Center (CNT) Notched Tension. Results showed that the Peeling testing was not an appropriate method to determine adhesion strength of overmolded specimens; at high melt temperatures, the fracture does not occur through the interphase but rather through the TPV. The CNT and DENT geometries showed very high data dispersion, caused by asymmetric crack propagation. The adhesion strength measurement can satisfactorily be done using EWIF-SENT or Tensile testing; however, only the former guarantees that the fracture takes place along the interphase.