The solid-melt interfaces between polyethylene (PE) and polyamide 6 (PA6) reinforced by in situ reactive compatibilization in a sequential two-staged injection molding process has been studied in this work. The effects of the maleic anhydride grafted PE content and processing parameters, such as injection pressure, injection speed, melt temperature, and mold temperature, on the interfacial adhesion were investigated experimentally. The results of the interfacial adhesion characterized by lap shear measurement showed that the interfacial temperature and heat transfer between PE and PA6 interfaces play a very significant role in the bonding process. The fracture surfaces of the specimens prepared at different calculated interfacial temperature were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), which suggested that the fracture failure changes from adhesive to cohesive failure with increasing interfacial temperature. The contribution of crystalline parts of the in situ formed copolymers to the enhancement in interfacial adhesion also was determined by DSC analysis. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1112-1124, 2009