Abstract
Melamine cyanurate (MC) acts as a fire retardant for a Nylon 6,6-Nylon 6 copolymer (PA) via a condensed-phase mechanism as shown by a parallel increase in oxygen index (OI) and nitrous oxide index (NOI) as a function of MC loading. MC induces melt dripping in vertically burning PA, which can enhance the OI because of heat elimination via molten material. However, MC also increases the OI when the PA/MC mixtures are burned in a cup, which prevents dripping. Thus, besides the well-known dripping-cooling physical action, another fire-retardant role is played by MC. This was studied by investigating the mechanism of thermal degradation of PA/MC mixtures by means of thermogravimetry (TG) and differential thermal analysis (DTA).
It was seen that volatilisation begins in PA/MC mixtures at a temperature lower than that expected on the basis of the behaviour of PA and MC heated separately. Burning in the cone calorimeter showed that MC decreases the time to ignition of PA and the heat release rate (RHR) in the first minutes of combustion, which could be related to the TG results.