Challenge to the production of low-density, fine-cell HDPE foams using CO2

This paper presents an experimental study on the manufacture of low-density fine-cell high density polyethylene (HDPE) foams in extrusion using CO2 as a blowing agent. The strategies adopted to produce low-density, fine-cell HDPE foams were to generate a large number of cells by a rapid pressure dro p, to suppress cell coalescence by strengthening the melt via melt temperat ure control, and to promote expansion by cooling the extrudate surface and blocking the gas escape. A continuous extrusion process has been designed a nd implemented based on these strategies. The concept of promoting large ex pansion while preventing cell coalescence to maintain a high cell density h as been successfully demonstrated through experiments. Low-density, fine-ce ll HDPE foams were produced with a expansion ratio in the range of 1.5 - 20 times, a cell density on the order of 10(8) cells cm(-3), and a cell size of the order of 50 mu m.