Smoke Production Behaviors Of Epoxy-Based Intumescent Flame Retardant Coating

Intumescent flame retardant (IFR) coatings have been widely used to protect substrates against fire, and they have attracted considerable attention in recent years because they are more environmentally friendly than the traditional halogen-containing flame retardant coatings. In addition, the IFR coatings present some outstanding advantages:they retain the intrinsic properties of the material (e. g. the mechanical properties), they are easily processed and employed on multiple substrates, such as polymers, metallic materials, wood and textiles. Epoxy resin (EP) is the most important material for IFR coatings as film former, because of its balance of excellent heat, solvent, moisture, and chemical resistance, good mechanical and electrical properties, and satisfactory adherence to many substrates. However, the pure EP is easily ignited and releases large quantities of heat, smoke and even toxic gases during combustion, hence exploring fire behaviors and smoke production properties of epoxy-based intumescent coatings has been a hot and challenging issue.In this article, smoke production behaviors and thermal stability of crosslinked epoxy/polyamide resin (EP/PA) in epoxy-based intumescent flame-retardant (IFR-EP) coatings have been investigated using cone calorimeter, smoke density instrument, thermalgravimetric and Fourier transform infrared spectroscopic (TGA-FTIR) and mass spectrometric analyses (TGA-MS). Furthermore, a comparative study about smoke suppression effect of IFR on EP/PA was carried out. And the smoke suppression and synergistic flame retardancy properties of zinc borate (ZB) and diantimony trioxide (Sb2O3) in epoxy-based IFR coating are investigated based on cone calorimeter, smoke density test, scanning electron microscopy, thermalgravimetric and the Fourier transform infrared spectroscopic analyses. What’s more, the smoke suppression effects of molybdenum trioxide, ferrocene and ammonium molybdate were also studied using cone calorimeter and smoke density instrument.The results show that the unique crosslinked structure in EP/PA suppresses the smoke production in the early combustion stage and strengthen the thermal stability during the whole degradation process, whereas the IFR effectively promotes the smoke suppression and flame retardancy properties of IFR-EP coatings in the late combustion stage. And with the decomposition and melt of ZB and Sb2O3, a lot of heat tends to be absorbed; and then the glassy protective layer associated with the graphite char will effectively retard the heat and suppress the smoke. The molybdenum trioxide shortened the smoke time, the ferrocene reduced the smoke release rate in the early stage of combustion, and the ammonium molybdate enhanced the smoke suppression in the later stage of combustion. Moreover, the coatings containing 10.3 wt% smoke suppressant have a better smoke suppression effect.