Development of HFC Blowing Agents. Part II: Expanded Polystyrene Insulating Boards

Abstract

The development of HFCs as blowing agents for rigid polyurethane foams has previously been reported11’. In this second paper, it will be seen that the Montreal Protocol and its subsequent reviews have also presented a challenge for the extruded expanded polystyrene (XPS) foam industry. CFC-12 has long been the main blowing agent in that application due to its unique properties such as non-flammability, non-toxicity, low thermal conductivity and good processability. In developed countries, the rapid phase-out of CFC-12 was made possible due to the availability of HCFCs. HCFC-142b, pure or in blends with HCFC-22 or ethyl chloride, has now become the reference blowing agent for XPS insulating boards world wide owing to its superior properties. This paper will discuss the current situation by providing some information about properties commonly found in laminated boards. A theoretical model is used to simulate their long term behaviour, especially thermal insulation. Using this theoretical model and available data, it is possible to gain an insight into foam performance that can be achieved by zero ozone depletion potential substitutes such as HFCs and carbon dioxide. HFC-134a appears to be the leading candidate particularly when the thermal insulation is needed.