Development of a pyrolysis model for glass fiber reinforced polyamide 66 blended with red phosphorus: Relationship between flammability behavior and material composition

Abstract

This work demonstrates an approach to building a material burning model capable of predicting the material's behavior as a function of concentration of a condensed-phase-active flame retardant. This approach relies on a newly developed gasification apparatus to measure back surface temperature, mass loss rate, and shape profile evolution for 0.07-m-diameter disk-shaped samples exposed to well-defined radiant heating in an anaerobic environment. Inverse analysis of these gasification measurements, using a predetermined thermal decomposition reaction mechanism, yields properties that define heat and mass transport in the pyrolyzing solid. In the current study, this approach is applied to a set of materials comprised of glass fiber reinforced polyamide 66 blended with red phosphorus. A single pyrolysis model is developed that relates the concentration of the additive to the material burning rate. During the model construction, it was revealed that, to successfully model pyrolysis of this glass-fiber-filled thermoplastic, it is important to take into account so-called wick effect, through which the molten polymer was transported toward the heated surface. Incorporation of this effect into the model enabled a more accurate prediction of the burning rate. Idealized cone calorimetry simulations were conducted to demonstrate that red phosphorus has a significant impact on the heat release rate. Any red phosphorus added above 2 wt% reduces both the first and second heat release rate peaks by approximately 38% and this reduction can be attributed to the condensed-phase thermal barrier effect and, to a lesser degree, dilution of the gaseous decomposition products with less combustible gases.