Advances in Thermal Insulation of Extruded Polystyrene Foams

Since their discovery in the early 40's extruded polystyrene foams (XPS) have been produced with various organic and inorganic blowing agents, and are now widely used as thermal insulators in building and construction. Blowing agent regulations have forced foam suppliers to look for new polymer - blowing agent - additive combinations. These must deliver high performance insulation, but must not compromise on high mechanical strength, foam integrity, and moisture resistance. This paper focuses on the thermal resistance of XPS blown with zero-ODP blowing agent (hydrofluorocarbon HFC-134a) and with carbon dioxide. IR-blockers such as carbon black and graphite reduce the thermal conductivity of CO ₂ blown XPS between 1 and 3×10 ^-3 W/m.K depending on the concentration of IR-attenuators. Properties of a new XPS product using CO ₂ with IR blockers are presented. This product is CE certified and fulfills the requirements of the European XPS product standard DIN EN 13164.