Cell development in microcellular injection molded polyamide-6 nanocomposite and neat resin

The effects of nanoclay addition into polyamide-6 (PA-6) neat resin and processing parameters on cell density and size in microcellular injection molded components are investigated. The analyses are performed on the sprue section of standard ASTM D 638-02 tensile bars molded based on a fractional four-factorial, three-level, L9 Taguchi design of experiments (DOE) with varying melt temperature, injection speed, super critical fluid (SCF) concentration, and shot size. It is found that the presence of nanoclay greatly reduced the cell size and increased the cell density when compared to neat resin processed under identical molding conditions. In addition, cell size distribution at the sprue center was, in general, the largest, gradually decreasing toward the skin for both the neat resin and the nanocomposite. Finally, in contrast to neat resin, in which shot size and injection speed were important to cell density and all molding parameters affected cell growth, the cell size and density for nanocomposite only depended strongly on shot size.