Instrumentation of UL-94 test: understanding of mechanisms involved in fire retardancy of polymers

A quantitative approach of phenomena occurring in UL-94 test setting up selected instrumentation was developed in this work. The instrumentation permits to measure the weight of droplets, the weight loss of the sample as well as the temperature gradients during the fire test. Three flame retardant formulations of PA6 exhibiting different modes of action (melamine cyanurate, melamine pyrophosphate, and guanidine sulfamate/melamine polyphosphate) were compared with the neat matrix and the corresponding formulations reinforced with 20wt% glass fibers. It was shown that depending on the mode of action of the flame retardant, the heat propagation, the volatilization and the release of drops are significantly different with or without glass fibers. The measured parameters include the endothermic effect of MCA, the volatilization of guanidine sulfamate/melamine polyphosphate, the formation of an intumescent barrier with melamine pyrophosphate and the measurement ex situ of the thermal diffusivity of the drops. From this approach, the behavior of the samples and the influence of glass fibers are understood. Copyright (c) 2015 John Wiley & Sons, Ltd.