Development of a multiple‐hole die for the production of single large blocks of low‐density polystyrene using carbon dioxide as a blowing agent

A multiple‐hole die for the production of single large blocks of polystyrene foam with carbon dioxide as blowing agent was developed. First, single‐hole die experiments were carried out with different hole sizes (2.0, 1.0, and 0.50 mm). Using these single‐hole dies dimensionally‐stable foam was produced with a density of 31 kg m−3 and an open cell structure. Next, the hole diameter and hole distances for a newly constructed multiple‐hole die were chosen on basis of the radial expansion in the single‐hole die experiments. Tests with the multiple‐hole die showed that the seven strings could melt together forming one large string with a diameter of about 20 mm and a density of 50 kg m−3. Therefore, the concept of using a multiple‐hole die for producing single large blocks of polystyrene was proven. However, larger block sizes were not possible because of the limited capabilities of the extruder. POLYM. ENG. SCI., 2011.