Extruded Polystyrene Foam: Propylene-Blown Log Let Out at 60 °C (McIntire, Dow 1948, Ex. 3, Test 3)

Extruded polystyrene foam blown with a propylene gas fraction instead of methyl chloride. Polystyrene stands two days at 40 °C with the propylene under pressure and becomes a gel. Let out at 60 °C (300 psi in the tower), it swelled into a log 11 inches across, weighing 3.08 lb per cubic foot, with small uniform cells. Source: O. R. McIntire (Dow), US 2,450,436 (1948), Example 3. Picture: the patent's drawing.