Influence of position and composition on adhesion to injection-molded TPO plaques as model automotive parts

Single lap shear adhesion measurements on model isotactic polypropylene and thermoplastic polyolefin (TPO) substrates which sandwich a chlorinated polyolefin (CPO) show similar values of the fracture strength, as determined from the stress at break, but much larger deformation at break for the substrates that contain a copolymer of ethylene with 9 wt% butane (EBR9) as an impact modifier. We also found for sections cut from a large format (300 × 100 mm) plaque of TPO12 (12 wt% EBR9), that the fracture energy increased as a function of distance from the gate. ATR-FTIR measurements on these sections indicated that there was a variation in the EBR content in the near-surface region of the substrate, and that stronger adhesion correlated with an increase of EBR content at or near the surface.