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Microcellular foamed polymeric products have found various applications depending upon their cell morphology. The microcellular injection molding process parameters have effect on the cell size, cell density and cell distribution. In order to develop desired cell morphology for a particular application, the set of injection molding parameters is required to be optimized for achieving a correct process window. In this paper an effort is made to study the effect of various injection molding processing parameters on cell morphology. Series of experiments were conducted for each of the processing parameter and the samples were observed under Scanning Electron Microscope (SEM). The trends of cell size and cell density with respect to the processing parameters were qualitatively analyzed. The results are useful for the processors who are interested in building up an understanding of this novel process and also to enable optimization of the set of processing parameters so that the desired microstructure of a foamed polymer can be obtained.

The microstructure of cellular materials, in particular microcellular polymers, is commonly characterized by the mean cell size and cell population density. Although the physical properties of foamed polymers are highly dependent on cell distribution, very insignificant work has been carried out to quantify the distribution of cells. This experimental study correlates the influential processing parameters of microcellular injection molding with the cell distribution, mean cell size and population density. For the first time, “Cell Distribution Index (CDI)”, a quantitative parameter for characterization of foams has been defined in this paper. Foamed samples of polystyrene were prepared via microcellular injection molding process. The design of experiment includes five influential processing parameters (factors) at five different levels. Molded samples were fractured cryogenically and micrographs were obtained using a table top scanning electron microscope. With the help of image processing package, mean cell size, cell population density, frequency and newly defined term CDI were calculated for each micrograph. Finally, the effect of processing parameters on cell distribution was analyzed by plotting the CDI against the processing parameters.

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