The PIR/PUR Ratio: A Novel Timer Conversion Tfst with High Correlation to the Factory Mutual Calorimeter for HCFC-141b Blown Polyisocyanurate Foams

Abstract

In response to the environmental dangers posed by CFC-11 use, rigid polyisocyanurate foam insulation manufacturers are currently making the transition to HCFC-141b. This change has forced manufacturers to requalify their commercial roofing products on the Factory Mutual Calorimeter. Factory Mutual certification is demanded by the marketplace, but the cost of attainment is high. With HCFC-141b technology being perfected, and its eventual replacement looming on the horizon, it is evident a great deal of Calorimeter testing will be required in the near future. There are a number of small scale tests in existence to measure fire resistance, but their effectiveness as predictors of Calorimeter performance has not been fully assessed. Trimer conversion is a crucial aspect of the fire resistance of polyisocyanurate foam, but a convenient and inexpensive measurement has not been documented. This paper introduces such a novel trimer conversion test, the PIR/PUR ratio. A high degree of correlation exists between Calorimeter results and the PIR/PUR ratio. Strong correlations also exist between the Calorimeter and certain other small scale tests. However, relying on only one test to predict calorimeter performance is insufficient. Consideration must be given to all relevant tests. Forming a composite index from the individually relevant test results, using weighted factor techniques, provides the best indication of Calorimeter performance. The information in this paper should enable polyisocyanurate insulation manufacturers to make better predictions of Calorimeter performance, avoiding costly failures.