Assessment of hydrofluoropropenes as insulating blowing agents for extruded polystyrene foams

Abstract

Thermally insulating extruded polystyrene foams are currently produced with hydrofluorocarbon blowing agents. Hydrofluorocarbons have zero ozone depletion potential but rather high greenhouse warming potential. Various unsaturated fluoropropenes, with greenhouse warming potential values <15, have been assessed as HFC-134a replacements for styrenic extrusion foaming. The screening is first based on the modeling of solubility and diffusivity properties, followed by foaming experiments with a conventional extrusion process. Some fluoropropenes appear to be excellent blowing agents for extruded polystyrene foams and can be used alone for making very low-density foams with regular and large cell sizes, while some others require the use of a co-blowing agent for processing good quality foam. A few others are not suitable as a blowing agent for extruded polystyrene foams due to their toxicity or their very poor transport properties.