Steven L. Schilling

Appliance Rigid Foams Blown with Cyclopentane and Cyclopentane/Isopentane Blends:

Since CFC 11 was eliminated from use in rigid foams in the mid 1990s, the blowing agent of choice in North America has primarily been HCFC 141b. In the USA, we are now faced with the phase-out of HCFC 141b by the year 2003. The blowing agent that will replace HCFC 141b must be non-ozone depleting and should also have low thermal conductivity and a low global warming potential. Hydrocarbons are some of the few blowing agents that meet these criteria and are approved by the United States Environmental Protection Agency to replace HCFC 141b in rigid polyurethane foams for appliance insulation [1]. Of the hydrocarbons being considered, cyclopentane is preferred, either by itself or in blends with other hydrocarbons. This is because of cyclopentanes favorable combination of low thermal conductivity, good solubility in polyols and reasonable boiling point, compared to other hydrocarbons. Not only is the thermal conductivity of cyclopentane lower than that of most other hydrocarbons, it is also lower than that of HFC 134a, another blowing agent which is approved for use after 2002. This paper will examine the effect of two important factors, both theoretically and experimentally, on cyclopentane blown foams. These factors are (1) the amount of blowing obtained from carbon dioxide that is formed from the reaction between water and isocyanate, and (2) the ratio of cyclopentane to isopentane, which is used as the hydrocarbon blowing agent.

Appliance Foams with Reduced Levels of HFC-245fa

The HCFC-141b blowing agent used in most appliance foams in the United States is scheduled for phase-out on January 1, 2003. The most promising replacement is HFC-245fa. It has met many of the requirements for a blowing agent such as zero ozone depletion potential (ODP), low toxicity, good miscibility with polyols, low vapor phase thermal conductivity, and a reasonable boiling point of 59.5°F (15.3°C). Also, because it is non-flammable, HFC-245fa will save manufacturers of household refrigerated appliances the costs associated with retrofitting their factories to safely handle flammable blowing agents. However, refrigerator manufacturers have concerns about higher product manufacturing costs. Foam insulation costs may rise. New processing equipment and procedures may need to be installed in factories for new blowing agents. Refrigerator producers want to know if their foam operation productivity and product quality will be affected. They are also concerned about staying compliant with the 2001 Energy Consumption Standards. This paper will report on work done at Bayer Corporation to address these concerns. We will show the effect of lowering the level of HFC-245fa on foam thermal conductivity, physical properties and demold characteristics. Thermal stability and pressure generation studies on HFC-245fa containing masterbatches are presented which provide insight into handling the new generation formulations. The information presented will assist household refrigerator producers in selecting the most cost-effective solution to their manufacturing concerns when replacing HCFC-141b with HFC-245fa.