Increase of open-cell content by plasticizing soft regions with secondary blowing agent

This article describes the effects of n-butane mixed with primary CO2 as a secondary blowing agent on the cell-population density, the volume expansion ratio, and the open-cell content of low-density polyethylene (LDPE) and LDPE/polystyrene (PS) blends in extrusion. With the plasticizing effect of n-butane, a high open-cell content (up to 100%) over a wide range of processing temperatures was successfully achieved.