DEVELOPMENT OF HFC BLOWING AGENTS - PART II - EXPANDED POLYSTYRENE INSULATING BOARDS

The development of HFCs as blowing agents for rigid polyurethane foams has previously been reported((1)). In this second paper, it will be s een that the Montreal Protocol and its subsequent reviews have also pr esented a challenge for the extruded expanded polystyrene (XPS) foam i ndustry. CFC-12 has long been the main blowing agent in that applicati on due to its unique properties such as nonflammability, non-toxicity, low thermal conductivity and good processability. In developed countr ies, the rapid phase-out of CFC-12 was made possible due to the availa bility of HCFCs. HCFC-142b, pure or in blends with HCFC-22 or ethyl ch loride, has now become the reference blowing agent for XPS insulating boards world-wide owing to its superior properties. This paper will di scuss the current situation by providing some information about proper ties commonly found in laminated boards. A theoretical model is used t o simulate their long term behaviour, especially thermal insulation. U sing this theoretical model and available data, it is possible to gain an insight into foam performance that can be achieved by zero ozone d epletion potential substitutes such as HFCs and carbon dioxide. HFC-13 4a appears to be the leading candidate particularly when the thermal i nsulation is needed.