Louise C. Speitel

The Federal Aviation Administration (FAA) has developed a unique extractive Fourier Transform Infrared (FTIR) system to analyze rapidly changing moist fire gas concentrations as a function of time. The system was designed to eliminate numerous errors generated by state-of-the-art FTIR systems for fire gas analysis. In addition, the path length, cell volume, sample flow rate, and system temperature were optimized to provide a rapid response and a sufficient dynamic range to detect gas concentrations generated in the cone calorimeter. A nonlinear classical least squares method was developed to analyze the FTIR data and generate the concentration histories and confidence limits of the 16 fire gases. Results of the technique are presented for flaming and nonflaming combustion tests of a mix of six common plastics.

Richard Walters and Richard E. Lyon

Specific heat release rate is the molecular-level fire response of a burning polymer. The Federal Aviation Administration (FAA) obtains the specific heat release rate of milligram samples by analyzing the oxygen consumed by complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat release rate (W/g) by the rate of temperature rise (K/s) gives a material fire parameter with the units (J/g-K) and significance of a heat (release) capacity. The heat release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical composition have been tested to date, providing over 40 different empirical molar group contributions to the heat release capacity. Measured and calculated heat release capacities for 80 polymers agree to within ±15%, suggesting a new capability for predicting flammability from polymer chemical structure.

Richard N. Walters

Experimental results for the gross heat of combustion of over 140 commercial and developmental polymers and small molecules of known chemical structure were used to derive additive molar group contributions. Predicted gross heats of combustion were within 2.5 percent of the values measured by oxygen bomb calorimetry.

Michael L. Ramirez, Richard Walters, Edward P. Savitski, and Richard E. Lyon

Polycyanurate networks were prepared by thermal polymerization of cyanate ester monomers containing two or more cyanate ester (–O-C≡N) functional groups. The thermal decomposition chemistry of nine different polycyanurates was studied by thermogravimetry and infrared analysis of solid films and analysis of the gases evolved during pyrolysis using infrared spectroscopy and gas chromatography-mass spectrometry. It was found that the thermal stability of the polycyanurates was essentially independent of monomer chemical structure with the major mass loss occurring at about 450°C for all materials. Analysis of the solid-state and gas phase thermal degradation chemistry indicates a thermal decomposition mechanism for polycyanurates which begins with hydrocarbon chain scission and cross-linking at temperatures between 400°-450°C with negligible mass loss, followed by decyclization of the triazine ring at 450°C that liberates volatile cyanate-ester decomposition products. The solid residue after pyrolysis increases with the aromatic content of the polymer and incorporates about two thirds of the nitrogen and oxygen present in the original material.

Richard E. Lyon, Lauren M. Castelli, and Richard Walters

The flammability, thermomechanical properties, and fire response of the diglycidylether of 1,1-dichloro-2,2-bis(4- hydroxyphenyl)ethylene (DGEBC) cured with several hardeners were examined and compared to diglycidylether of bisphenol-A (DGEBA) systems. The DGEBC and DGEBA were cured with (1) triethylenetetramine, (2) methylenedianiline, (3) the parent phenol (BPC or BPA), (4) catalytic amounts of (2-ethyl-4-methylimidazole) (EMI-24), and (5) the dicyanate of bisphenol-C. Cured samples were measured for strength, modulus, flame resistance (limiting oxygen index (LOI), UL-94 V), flaming heat release rate, and heat release capacity. The mechanical properties of the DGEBC and DGEBA systems were equivalent but the DGEBC systems exhibited superior flame resistance and 50% lower heat release rate and heat release capacity than the corresponding DGEBA system. The DGEBC cured with methylenedianiline had an LOI of 30-31, exhibited UL 94 V-0/5V behavior and easily passed the Federal Aviation Administration heat release requirement Federal Aviation Regulation 25.853 (a-1) as a single-ply glass fabric lamina.