ABSTRACT
With the elimination of HCFC-141b in the United States over the next few years, appliance manufacturers have two major categories of blowing agents to choose from as potential replacements. Hydrocarbons offer low raw material costs, high capital costs and a moderate to high cabinet energy consumption. A large amount of work has been performed outside the United States on hydrocarbon usage, with successful manufacturing implementation. However, it appears that the combination of cabinet energy penalties, capital conversion costs and flammability concerns are currently detouring appliance manufacturers from choosing this route for the next blowing agent in the U.S.
The second major option is gaseous blowing agents, either Hydrofluorocarbons (HFC’s) or Hydrochlorofluorocarbons (HCFC’s). The most common of which include HFC-245fa, HFC-365mfc, HCFC-142b, HCFC-22 and HFC-134a. Of the potential HCFC-141b replacements, many appliance manufacturers have chosen to use HFC-245fa since this yields the lowest cabinet energy consumption. The biggest drawback to HFC-245fa has been the cost of the material and the perceived difficulty in passing the increased costs along to the consumer in the appliance market. A blend of HCFC-142b/HCFC-22 offers another option with similar k-factor and factory costs, but a significantly lower raw material cost at the head. The major problem with this blend is its timeline for acceptance. Depending on the EPA’s latest ruling, the phase out date for these materials could potentially move from 2010 to 2005 in the United States.
Another option is HFC-134a, as it produces a moderate cost part but at a penalty in cabinet energy consumption. Recent developments using HFC-134a provide data that address these two shortcomings prompting another look at this potential blowing agent. A new polyol was developed which significantly improved the thermal conductivity of foams produced using HFC-134a. The new polyol is responsible for lowering thermal conductivity of the foam from 0.152 to 0.147 btu. This k-factor improvement could provide near equivalent cabinet energy performance to a hydrocarbon based appliance system without the flammability issue. Another option recently identified is a reduced cost HFC-134a system. This system has both a lower head cost, due to a reduced level of the HFC-134a, and a reduced in-place density, while maintaining the k-factor of the system. This combination reduces the overall cost of the system by greater than 10%. Both of these improvements make foams blown with HFC-134a more attractive than in the past.
