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 cyclopentane's 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.