Abstract
The phaseout of HCFC-141b as a blowing agent for rigid foams is scheduled to begin in 2003 or sooner. The blowing agent to replace it should have low thermal conductivity, zero ozone depletion potential (ODP), low global warming potential (GWP) and be low in toxicity. In addition, other desirable characteristics include good compatibility with polyols, stability of the blowing agent by itself and in masterbatches, ease of handling, compatibility with plastic food liners, reasonable cost and feasibility of manufacture, good processing characteristics in machinery and no flammability. Finally, the blowing agent should produce foams having insulation properties which are comparable to or better than those made with HCFC-141b.
Considerable effort is being directed to developing new appliance foam systems for North America which use blowing agents that have many or all of these characteristics. A number of candidates have been evaluated from which HFC-245fa meets the majority of these criteria if not all of them. Bayer Corporation reported data on HFC-245fa blown appliance foams which had most of these characteristics. Energy performance in cabinets was less than 1% poorer with the HFC-245fa foam versus an HCFC-141b commercial foam.
For the future, energy standards in the United States will become 25 to 30% more stringent after July 1, 2001. Therefore, the insulation value of HFC-245fa foams will most likely have to be better than foams blown with HCFC-141b. This paper will discuss new developments with HFC-245fa blown appliance foams. Results of a design of experiments to study the effects of catalyst levels, the processing temperatures of the masterbatch and the isocyanate and the viscosity of the formulation on physical properties will be presented. Results will be compared to a previously reported HFC-245fa system and to an HCFC-141b commercial system.
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