General aspects of foam injection molding using local precision mold opening technology

By using a special mold technology, it is possible to produce injection molded components with locally graded foam structures and locally different densities. This paper describes general results of foaming polypropylene with chemical and physical blowing agents. Particularly, the characteristics of the density in the different foamed areas and the mechanical properties depend on the process-specific process parameters. Differences in terms of processing in comparison to typically precision mold opening geometries result from the limited foamed areas of the locally foamed component. Whereas the density reduction in the highly foamed areas is directly set by the process, the density in adjacent thin-walled areas results as a function of process control. The structure formation, and thus the specific mechanical properties can also be influenced by the process parameter settings.