Compounding and injection molding are processes which normally take place locally and temporally separated at the raw material supplier and the product manufacturer. These processes are combined by the use of an injection-molding compounding system. This production line, which has been designed for the processing of long fibers in the first place, was specially adapted for the manufacturing of polymer nano¬composites (PNCs). This work focuses on the one hand on the processing of layered silicates using the injection molding compounder and on the other hand on the activation of polypropylene PNCs using elongational flows. The material development of nano-reinforced thermoplastics is compared between the conventional 2-step process and the injection molding compounding process (1-step). In addition to the optimization of the compounding process (process, screw configuration and formulation) special focus was set on the manufacturing of the test specimens. Choosing the proper molding parameters leads to changes in the mechanical properties of up to 8 %. The additional activation of PNCs by elongational flows for the improvement of the mechanical properties was another important part of this work. The aim was to replace the time consuming masterbatch (MB) process through the energy-saving and cost-effective 3-in-1 process (simultaneous dosing of all three components of the polypropylene PNCs). By means of systematical variations of conical and hyperbolical nozzles in a full factorial experimental design, it was possible to improve the mechanical properties of the 3-in-1 process to a level which is 10 % higher than reachable with the conventional MB-process. By using an optimized hyperbolic nozzle only an additional pressure of around 75 bar compared to the standard injection molding nozzle is required. In addition to the practical investigations a calculation program for the prediction of temperature and pressure increase was used which provided good guidance for the design of the elongation flow generating nozzles. In summary this work shows that the use of elongational flows in the 3-in-1 process has great potential for the production of PNCs which also when coupled with an injection molding compounder can lead to remarkable energy- and cost-savings. The scientific and technical basis for the industrial implementation of elongational flow generating nozzles in combination with the injection molding compounder is set.