ABSTRACT
Building Codes in the United States require that insulation materials meet defined standards of flammability performance. For roof insulation in particular, the Factory Mutual Calorimeter test (part of the FM 4450 test procedure), and Underwriters Laboratories 756 procedure, among others, are critical performance criteria. Optimization of the flame-retardant type and use level is a key component in the formulation of polyisocyanurate foams to meet the applicable flammability standards.
Traditionally, the industry has used small-scale methods in an attempt to predict performance in the full-scale flammability tests. These methods have been convenient and inexpensive, but have not been entirely satisfactory as predictive tools.
The previous small-scale flammability screening tests have now been improved upon with the development of an inexpensive larger-scale screening test that duplicates the exposure temperatures of the full-scale tests. Assessment of char formation, weight and dimension retention, and char integrity can be made as a function of the flame- retardant type. The isocyanate, polyol, catalyst and flame- retardant package can be evaluated identify materials that minimize cracking and shrinkage, and maximize the thickness retention of the char. The apparatus also provides for the testing of up to four samples simultaneously, under identical conditions.
Data is presented to demonstrate he correlation of the new test procedure to the existing FM and UL tests. Recommendations are made for flame-retardant combinations that provide the highest degree of char integrity. A list of materials, cost estimate, and design drawing of the apparatus is also included.
