Spray Foam Beyond HCFC-141b

Abstract

Sprayed rigid foam is a significant segment of the polyurethane industry, and as in other rigid foam segments, spray foam formulators need to find ways to meet current product requirements when the use of HCFC-141b is phased out in January 2003. Due to some of the unique characteristics of the spray foam industry, though, the choice of a replacement blowing agent is perhaps more complex than in any other rigid foam sector. The alternatives receiving the most consideration today are HFC-245fa, hydrocarbons, and water. All of these potential blowing agents have significant hurdles to overcome before they could serve as satisfactory replacements for HCFC-141b in the spray foam market. As of May 1999, a firm commitment to commercialize HFC-245fa has not been made. The use of hydrocarbons in spray would require significant improvements in safe handling procedures and modifications to spray equipment due to flammability issues. And with water-blown systems, dimensional stability and adhesion are two technical hurdles that must be overcome. It is conceded as well that insulation performance (as measured by initial k-factor) will not be as good for a water-blown foam as with HCFC-141b. It was because of the lack of an obvious HCFC-141b replacement for the spray foam industry that Huntsman Polyurethanes decided to investigate possible solutions. Any alternative would need to meet the processing and handling requirements that are currently met with HCFC-141b systems. The objective of this work is to develop zero-ODP (ozone depletion potential) technology that meets the performance characteristics that are currently achieved with HCFC-141b spray foam roofing systems. The focus of this paper is on the development of water-blown technology for roofing systems. Foams were processed via high-pressure spray equipment in a controlled environment. The study looked at the effect of polyol, catalyst, blowing agent, and processing variables on foam quality.