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Bayer Corporation Study Finds Appliance Foam Thickness has Major Effects on Several Key Foam Properties

Bayer MaterialScience AG : 14 October, 2002  (Company News)
Based on a Bayer Corporation study of important processing variables for rigid polyurethane foam insulation, refrigerator manufacturers should carefully consider the effects of wall thickness on the processing and physical properties of the foam when designing new products.
As the study of third generation blowing agents that will replace HCFC-141b at the end of 2002 found, thicker foam insulation can be lower in density, but also results in more swelling and can actually increase the foam's k-factor, which can affect the appearance and energy efficiency of the appliance.

Bayer scientists conducted a systematic study of the effects of important variables on the processing and physical properties of rigid polyurethane foam insulation blown with three different third generation blowing agents - HFC-245fa, HFC-134a and cyclopentane. They also included HCFC-141b, the current blowing agent that will be phased out in the United States at the end of 2002 for use in foam blowing under the terms of a regulation promulgated by the U.S. EPA.

Bayer was interested in how foams would be affected by common processing variables and parameters, given the vastly different physical properties of these next generation blowing agents.

Kevin Elsken, Steven Schilling, Michael Han and William Tingler, all of Bayer's Polyurethanes Division, presented the study in a poster paper at the Alliance for the Polyurethanes Industry (API) Polyurethanes 2002 technical conference here this week. The poster title was 'Processing Study of Appliance Rigid Foams with Third Generation Blowing Agents.'

'All of the factors studied had a significant effect on at least some of the foam properties we evaluated, but the mold thickness stood out as the most important factor for a number of different properties. We believe this is because the mold thickness had such a large influence on the foam density, which in turn affects other properties,' explained Steven Schilling, Principal Scientist for Bayer.

Thicker walls are often used to improve the appliance's insulation and energy performance. However, the thicker walls can also increase the foam's k-factor and reduce the foam's density, while increasing its demold swelling and perpendicular compressive strength.

Thinner walls are most often used to increase refrigerator interior volume. However, thinner walls tended to increase the foam's density and parallel compressive strength while reducing the k-factor and demold swelling.

'Manufacturers must now meet more stringentgov ernmentenergy efficiency requirements in the United States while also trying to minimize their overall costs. We suggest that they carefully consider the effect of wall thickness on the properties of the rigid polyurethane foam insulation when designing new appliances,' Schilling said.

'Increasing or decreasing cabinet wall thickness may be an effective route to producing a more efficient or less costly refrigerator, but the change could also produce undesirable consequences,' he explained.

Kevin Elsken, Development Scientist for Bayer, added, 'Designers should remember that the foam properties of a given rigid polyurethane foam system are a function of the cabinet design it fills. A system that is optimal for one design may not be the best for another.'
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