Manufacture and model calculation of porcelain-like microcellular low-density polystyrene foam

It is a well known that nucleation by gases in the supercritical state lead to high-density nanocellular foams, but the aim of this article was to find a route to microcellular low-density closed-cell foam with expected low heat conductivity and high mechanical properties. Polystyrene was impregnated with carbon dioxide or propane at room temperature and 70 bar pressure. Pentane served as a reference substance. The samples were investigated by electron microscopy. The specimens comprising carbon dioxide and propane showed bubbles surrounded by a ring of lamellas. The samples were foamed in hot bathes of silicone, of saturated NaNO3 water solution, and in water vapor under stretching conditions at 100? or 110?. The foaming was registered continuously on a balance by buoyancy experimentally and calculated in diffusion as well as viscosity-controlled foaming models. A microcellular foam with 35kg/m(3) density, 1.5 mu m or 1500nm cell diameter, 5.5MPa tear strength, and 0.027W/m.K heat conductivity was obtained, which looked like porcelain. The continuous manufacture of low-density carbon dioxide or propane foam by extrusion did not lead to microcellular foam, because the necessary high-pressure, low-temperature nucleation conditions could not be performed.