Appliance Design - March 2009 - (Page 34)

INSULATION Alternative Blowing Agents e han e t uret poly ecoma of cks wn with Blo blo t. foam g agen in blow Global warming issue drives new developments. he saga of alternative blowing agents for polyurethane foam insulation seems never-ending, and new chapters are still being written. In both residential and commercial refrigeration applications, the blowing agent CFC-11 had been the standard for years until banned by the Montreal Protocol because of its ozone depletion potential (ODP). Given the challenges of quickly finding ideal alternatives, HCFCs such as HCFC-141b, with a somewhat lower ODP, were approved as a temporary alternative until better blowing agents could be found. With the eventual mandated phase-out of that chemical, manufacturers diverged down one of two paths — hydrocarbons or hydrofluorocarbons (HFCs). Those concerned about the flammability of hydrocarbons selected one of several HFC options. But as global warming has risen on the political and public agenda, the high GWP values of the HFCs have raised questions about their long-term future as blowing agents and has everybody involved rethinking the issue yet again. Not surprisingly, this was a hot topic at the Polyurethanes 2008 Technical Conference held in San Antonio, Texas, in September 2008, and the Insulation Options Technical Session featured a number of papers addressing it. Three of those papers are summarized here. T Arkema Investigation of New Low-GWP Blowing Agents for Rigid Polyurethane Foams, by Ben Chen, Joseph Costa, Philippe Bonnet, and Maher Elsheikh, Arkema, King of Prussia, Pa.; and Laurent Abbas, Arkema France, Pierre- by richard babyak 34 applianceDESIGN March 2009 Benite, France. The need for insulation materials with improved energy efficiency and environmental profiles has led Arkema to investigate a range of low-GWP blowing agents designed for most PUR applications, including appliances, pourin-place, spray, and PIR boardstock. These fourth-generation blowing agents — the AFA series — are being developed in both liquid and gas formulations to replace HFCs such as 245fa and 134a. All the AFA molecules have very low GWP values, less than 15, and negligible ODP values. Both AFA-G1 and AFA-G2 have a lower flammability limit (LFL) at ambient temperature. However, AFA-L1 did not exhibit either a flashpoint (FP) or flammability limit under ambient conditions. Both AFA-L1 and AFA-L2 exhibit a low gas-phase thermal conductivity (Lambda), comparable to HCFC-141b, which should contribute to the insulation value of the rigid polyurethane foam. Both liquid and gaseous versions of the blowing agents were evaluated in regards to blowing efficiency, dimensional stability, and insulation properties. The two experimental gaseous blowing agents, AFA-G1 and AFA-G2, were compared with HFC-134a. The Free Rise Density figures for the gases indicated that AFA-G1 (1.79) showed better blowing efficiency than either the AFA-G2 (2.03) or the HFC-134a (1.98). In terms of dimensional stability both of the experimental blowing agents performed better than HFC-134a blown foam. The shrinkage exhibited for the three blown foams was -5.0 percent volume change for the AFA-G1 foam; www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - March 2009

Appliance Design - March 2009 Contents Editorial Shipments/Forecasts News Watch Transmitting Power Wirelessly Promises to Reduce the Ever-Growing Tangle of Cords and Cables Found in the Modern Home. There Are Different Technological Approaches for Achieving this Goal, and Some Are Already on the Market. Electrochemical Capacitors Can Provide an Extra Peak-Power Boost in Battery-Operated Appliances, Allowing Product Designs to Have Smaller Battery Packs. Metallic Foams Put the Properties of Metals into Lightweight Packages. Applications for this Emerging Technology Include Gas Burners, Heat Exchangers, and Electronics Housings. Hall-Effect Switches Are Compact and Provide a High Degree of Reliability and Durability as They Virtually Eliminate Mechanical Wear, Shock, and Contact Oxidation. Blowing Agents for Polyurethane Foam Insulation Face Increased Scrutiny Due to Global Warming Concerns, but Alternatives with Lower GWP Values May Provide Solutions to Meet These Challenges. Design Marts Association Report: AHAM Advertisers' Index

Appliance Design - March 2009

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