The objective of this study deals with the analysis of the adhesion mechanisms on two-component composites in which the vulcanisate was sprayed on to thermosetting plastic inserts. The investigations start from the assumption that not only positive locking in the form of micromechanical interlocking but also chemical or physical interactions constitute the causes of the adhesion. The results show that the geometrical structure of the joining face of the insert exerts a decisive influence on the attainable composite adhesive strength and the adhesive strength increases along with the roughness. In addition to the enlargement of the effective surface, the cause may be attributed to microinterlocking rising along with the roughness. However, the results of the investigations with inserts with the same roughness and different chemical conditions of the joining face also show that the chemical condition of the joining face leads to characteristic adhesive strengths. A comparison of the results of both influences shows that the decisive influence lies in the surface roughness, the objective must be high roughnesses for maximum adhesive strengths and, in relation to practical implementation, the surfaces of the tool for the manufacture of the thermosetting plastic base body and thus of the joining face of the thermosetting plastic moulding must be provided with corresponding roughnesses. Furthermore, the results show that both freshly injected and tempered thermosetting plastic subassemblies enter into adhesion with elastomers. The extent to which the chemical or physical "activation" of the joining zone surfaces coming into contact in the composite can be influenced or raised constitutes one main focal point of currently ongoing investigations and cannot yet be evaluated at the present point in time.