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Abstract To enable intelligent design of fire resistant polymeric materials, it is highly important to have a quantitative understanding of the relation between the composition of these materials and chemical and physical properties that control the process of fire growth. This paper presents a methodology that provides a capability to determine the core subset of these properties including the kinetics and thermodynamics of the thermal decomposition of the condensed-phase constituents and enthalpy of combustion of gaseous pyrolyzates. This methodology is based on three experimental techniques – Thermogravimetric Analysis, Differential Scanning Calorimetry and Microscale Combustion Calorimetry – and inverse numerical modeling of the results of these tests. The material system analyzed in this study is polyamide 66 reinforced with chopped glass fiber and flame retarded with red phosphorous. This system shows a complex decomposition behavior that is highly dependent on the phosphorus concentration. First, a semi-global thermal decomposition mechanism consisting of a set of first- and second-order (two components) reactions was developed using three material specimens containing different phosphorus concentrations. Subsequently, the extrapolative power of the developed reaction model was demonstrated by accurately predicting the experimental measurements obtained for several compositions not used in the model development process. [ABSTRACT FROM AUTHOR]

This work details a methodology for parameterization of the kinetics and thermodynamics of the thermal decomposition of polymers blended with reactive additives. This methodology employs Thermogravimetric Analysis, Differential Scanning Calorimetry, Microscale Combustion Calorimetry, and inverse numerical modeling of these experiments. Blends of glass-fiber-reinforced polybutylene terephthalate (PBT) with aluminum diethyl phosphinate and melamine polyphosphate were used to demonstrate this methodology. These additives represent a potent solution for imparting flame retardancy to PBT. The resulting lumped-species reaction model consisted of a set of first- and second-order (two-component) reactions that defined the rate of gaseous pyrolyzate production. The heats of reaction, heat capacities of the condensed-phase reactants and products, and heats of combustion of the gaseous products were also determined. The model was shown to reproduce all aforementioned experiments with a high degree of detail. The model also captured changes in the material behavior with changes in the additive concentrations. Second-order reactions between the material constituents were found to be necessary to reproduce these changes successfully. The development of such models is an essential milestone toward the intelligent design of flame retardant materials and solid fuels. [ABSTRACT FROM AUTHOR]

Abstract This work details an approach to the development of a model of polymeric material fire behavior and its relation to flame retardant content. This approach employs a new controlled atmosphere pyrolysis apparatus to measure mass loss rate, back surface temperature, and sample shape profile evolution for 0.07-m-diameter disk-shaped samples exposed to well-defined radiant heating. Interpretation of these measurements using a thermal decomposition reaction mechanism, derived from thermal analysis experiments, and a numerical pyrolysis model, ThermaKin, yields properties that define heat and mass transport in the pyrolyzing solids. In the current study, this approach was extended to the analysis of flame retardant materials and applied to a set of materials comprised of glass-fiber-reinforced polybutylene terephthalate blended with aluminum diethyl phosphinate and melamine polyphosphate. Additionally, this work found evidence of so-called "wick" effect through which the molten polymer, when blended with glass fiber, was observed to be transported from regions of higher concentration to regions of lower concentration. Incorporation of the wick effect into the pyrolysis model was required to correctly capture the pyrolysis dynamics. The resulting pyrolysis model was found to be capable of predicting mass loss rate data as a function of material composition and external radiative heat fluxes ranging from 30 to 60 kW m−2 with an average error of 15%. Using heats of complete combustion of gaseous decomposition products determined in an earlier work, idealized cone calorimetry simulations were conducted to show that, when the gas-phase combustion inhibition effect is excluded, aluminum diethyl phosphinate has a relatively minor impact on the heat release rate, while the impact of melamine polyphosphate is significant. This work demonstrates, for the first time, that it is possible to establish a quantitative relation between the burning rate and material composition and thus, enables intelligent design of flame retardant materials tailored for specific applications. [ABSTRACT FROM AUTHOR]

Brominated flame retardants (BFRs) are widely used in polymers due to their high effectiveness at relatively low cost. Recent studies suggest that certain BFRs may present health and environmental hazards, yet obtaining adequate replacements is an ongoing challenge. To develop new additives, it is of paramount importance to better understand the mechanisms governing the action of flame retardants in polymers, particularly their action in the gas phase, and to develop effective screening techniques for potential candidates. To address this challenge, a novel apparatus, the Milligram-scale Flame Calorimeter (MFC), is proposed. In MFC, the pyrolysis and gas-phase combustion processes are uncoupled. Samples of 35 ± 5 mg are pyrolyzed in an anaerobic atmosphere and their pyrolysis products are burned in a laminar, near axisymmetric diffusion flame under controlled and customizable conditions in a fully enclosed system. Heat release information is obtained through the oxygen consumption calorimetry. The masses of post-combustion pyrolysis residue and solid particulate combustion products (e.g., soot) are measured. In this manuscript, a description of the design, parametric optimization of test conditions, and overall testing methodology is given. Heat release measurements are presented for polystyrene with increasing amounts of brominated polystyrene as well as poly(butylene terephthalate) with increasing concentrations of aluminum diethylphosphinate and results are compared to the Cone Calorimetry (Cone) and Microscale Combustion Calorimetry (MCC) measurements conducted on the same materials. Using combustion efficiency as a metric, the sensitivity to both bromine and phosphorus gas-phase activity is determined. The impact of these flame retardants is pronounced in the Cone experiments and largely undetected by the MCC. The MFC shows trends with respect to the flame retardant content comparable to the Cone. However, the absolute values of MFC combustion efficiencies tend to be notably higher that those observed in the Cone experiments. Overall, the MFC results demonstrate that this novel apparatus can be used to detect gas-phase activity of flame retardants using milligram-sized samples. [ABSTRACT FROM AUTHOR]