Baseline investigations of strength mechanism of hybrid material welds

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Hybrid materials, so-called polymer blends, are produced to combine the advantages of the basic materials, to enforce them through synergies or to adjust certain properties of the compound. Miscibility of different polymers is only known for very few composite materials. In case of incompatible polymers physical or chemical compatibilizers can be used to achieve certain miscibility in the boundary layer between the components. The aim of the research project is to weld polyolefins and polyamide together and to understand the mechanism of strength behind. The two sorts of polymer are incompatible as raw materials and therefore do not develop sufficient mechanical properties during the welding process for technical applications. To change the condition of immiscibility in a positive way the material of one joining partner is chemically modified in a previous moulding process. Thereby maleic anhydride as compatibilizer is bounded to the macromolecules of the polyolefins by reactive extrusion. The compatibilizer allows a limited miscibility of the different polymers in addition. The reactive blends are welded to a joining partner of non-modified polymer and the process parameters are varied concerning optimal mechanical properties. The research work covers hot plate welding and vibration welding processes. The choice of the welding processes is based on the fundamental differences in heat transfer and in rheological conditions during the joining phase. In hot plate welding the joining area is melted by heat conduction and the two joining partners are joined afterwards. In vibration welding process the two phases of heating by friction und joining take place at the same time. Thereby it exists the potential that different conditions of blending can be found in the joining layer. Mechanical and physical material properties of the compounds and the welds as well will be characterized with state-of-the-art analytical procedures to investigate the strength mechanisms and the morphology. With broad understanding of the mode of action by the investigated hybrid material welds it is possible to transfer the results to other material combinations.