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CFC blowing agents have been eliminated from virtually all polyurethane foam applications and replaced, in many cases, with the more environmentally acceptable HCFCs. In many applications the preference has been to convert from one liquid blowing agent to another, i.e., from CFC-11 to HCFC-141b. With the planned phaseout of HCFC-141b less than a decade away, there is a clear need for a "next generation" liquid blowing agent to eventually replace HCFC-141b. Previously, we reported the results of preliminary performance evaluations of four promising liquid HFC blowing agent candidates and the screening process used to select those four candidates. In this paper we discuss the environmental, toxicological and performance characteristics of our primary liquid HFC blowing agent candidate. The first criterion for a new blowing agent is environmental acceptability. A candidate must have a zero Ozone Depletion Potential (ODP) and a low Global Warming Potential (GWP), and should be free from other environmental concerns. Accordingly, the paper begins with a discussion of environmental properties such as atmospheric lifetime and GWP. It is equally important that the toxicological properties of a blowing agent candidate be well understood. The results of early toxicity tests have been very promising. These are reported along with a proposed timetable for additional toxicity testing. Ultimately, the acceptability of a new blowing agent will be based on performance. Data from laboratory foam evaluations involving both polyurethane and polyisocyanurate foams are presented. In addition to foam properties, other key performance characteristics such as plastics compatibility, blowing agent stability, foam premix stability and decomposition have been evaluated and are discussed.

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