SUMMARYSeven halogen-free flame retardant (FR) compounds were evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. Performance of wires coated with the compounds was evaluated using industry standard flame tests. The results suggest that time to peak heat release rate (PHRR) and total heat released (THR) in cone calorimetry (and THR and temperature at PHRR in PCFC) be given more attention in FR compound evaluation. Results were analyzed using flame spread theory. As predicted, the lateral flame spread velocity was independent of PHRR and heat release capacity. However, no angular dependence of flame spread velocity was observed. Thus, the thermal theory of ignition and flame spread, which assumes that ignition at the flame front occurs at a particular flame and ignition temperature, provides little insight into the performance of the compounds. However, results are consistent with a heat release rate greater than about 66 kW/m 2 during flame propagation for sustained ignition of insulated wires containing mineral fillers, in agreement with a critical heat release rate criterion for burning. Mineral fillers can reduce heat release rate below the threshold value by lowering the flaming combustion efficiency and fuel content. A rapid screening procedure using PCFC is suggested by logistic regression of the binary (burn/no-burn) INTRODUCTIONTesting of flame retardant (FR) materials presents technical and scientific challenges. Various enduse applications have unique fire tests, which in most cases have not been correlated to small-scale methods of flammability assessment. To complicate matters further, these tests are often conducted on finished articles rather than pure polymer compounds. Limiting oxygen index (LOI) and cone calorimetry are among the most commonly cited methods for assessing flammability of FR polymer compounds. Although studies have raised questions about the reliability of LOI in flammability research [1, 2], LOI remains one of the most popular flammability test methods. This is likely due in large part to the fact that measurement of LOI can be done quickly using relatively inexpensive and simple equipment. Despite its popularity, correlation of LOI with performance in industry flame tests is limited, and application to predict burn behavior in actual fires is uncertain [3].Cone calorimetry is another method for flammability assessment of materials, and can be run on raw materials as well as fabricated articles, providing a wealth of data from measurement of a single specimen. While cone calorimetry is steadily gaining in popularity, its use outside of research remains limited due to a number of factors, including the high cost, complexity of cone calorimeters, and the resources required to operate and maintain them. Additionally, there is no widespread agreement in the industry about which parameters are most meaningful. Therefore, more studies correlating burn performance in key industry tests with results of cone calorimetry on compounds are needed.Cone calor...

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