Abstract Blends of polyamide 12 (PA12) and liquid polybutadiene (HTPB) compatibilized with pyromellitic anhydride (APy) were prepared by melt blending. 10%, 12% and 20% HTPB blends were prepared, with various amounts of APy. The influence of the amount of APy on the morphology of the blends was studied for a wide composition range in the 12% series. Injection moulded tensile and Charpy testing bars were prepared from 10% and 20% binary and compatibilized blends. The deformations of the matrix under room temperature impact and the morphology of the blends were investigated with scanning electron microscopy. Partial miscibilization of HTPB with PA12 due to the addition of APy was postulated to explain the disappearance of polybutadiene in some cases. The mechanical properties of the blends were correlated with morphological parameters. A strong correlation between impact fracture toughness and the amount of non-miscible HTPB was found.