Zhi-sheng Xu

Correlations Between Measurements of Flame-Retarded High-Density Polyethylene Composites Subjected to Three Conventional Fire Tests

The flammability of halogen-containing and halogen-free flame-retarded high-density polyethylene (HDPE) composites was characterized by UL94, limiting oxygen index (LOI), and cone calorimeter tests. Correlations among the data obtained from UL94, LOI, and cone calorimeter tests were analyzed, while the influences of flame-retardant mechanism and burning condition on the correlations were also discussed. Analysis of UL94 rating shows that there is modest correlation between UL94 rating and LOI value in that it is able to differentiate between UL94 HB and V-2/V-0 rating, and no correlations for UL94 rating and cone calorimeter measurements are found due to the differences in flame-retardant mechanisms and burning conditions. The precise correlations are found between LOI value and some cone calorimeter measurements (peak heat release rate and mean heat release rate at 300 s). However, there are weak correlations between LOI value and some measurements (time to ignition, total heat release, mean heat release rate at 180 s, and fire growth rate index) and no correlations for other measurements (mean heat release rate at 60 s and mean heat release rate at 120 s) in cone calorimeter. Meanwhile, there are significantly different fitted equations and coefficients between LOI value and cone parameters for halogen-containing and halogen-free formulations due to the obvious differentiation in flame-retardant mechanisms. The comprehensive discussion of burning conditions could further explain why the correlations among the data obtained from the three fire tests have significant discrepancies and also help to understand why different flame-retardant effectiveness appears in the three fire tests.