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.

Michael Burns and William M. Cavage

A series of aircraft flight and ground tests were performed by the Federal Aviation Administration (FAA) and the Boeing Company to evaluate the effectiveness of ground-based inerting (GBI) as a means of reducing the flammability of fuel tanks in the commercial transport fleet. Boeing made available a model 737-700 for modification and testing. A nitrogen-enriched air (NEA) distribution manifold, designed, built, and installed by Boeing, allowed for deposit of the ground-based NEA into the center wing tank (CWT). The fuel tank was instrumented with gas sample tubing and thermocouples to allow for a measurement of fuel tank inerting and heating during the testing. The FAA developed an in-flight gas-sampling system, integrated with eight oxygen analyzers, to continuously monitor the ullage oxygen concentration at eight different locations. Other data such as fuel load, air speed, altitude, and similar flight parameters were made available from the aircraft data bus. A series of ten tests were performed (five flight, five ground) under different ground and flight conditions to demonstrate the ability of GBI to reduce fuel tank flammability.

The CWT was inerted with NEA to approximately 8% oxygen concentration by volume for each test. The aircraft condition was then set (fuel load, wind condition, and flight condition), and the oxygen concentration in the CWT was continuously monitored. Results showed that, under quiescent conditions, the oxygen concentration in the fuel tank remained somewhat constant, keeping the CWT inert (below 10 to 12% oxygen by volume) for relatively long periods of time. However, due to the cross venting configuration of Boeing aircraft, certain wind conditions created cross venting within the CWT which allowed for significant increases in the oxygen concentration. Some flight conditions also contributed to cross venting and created high oxygen concentrations within the fuel tank. A modification to the vent system prevented cross flow within the CWT and created a significant increase in the amount of the time the tank remained below 10% oxygen, even at low to moderate fuel loads.

Timothy R. Marker and John W. Reinhardt

This report describes full-scale fire tests conducted by the Federal Aviation Administration (FAA) to investigate the effectiveness of several types of water spray systems against in-flight cargo compartment fires. Currently, commercial transport cargo compartments are protected with Halon 1301 fire suppression systems. Water spray is being considered as an alternative agent for Halon 1301 which is no longer being produced because of its ozone depletion potential. A dual-fluid (air/water) nozzle system, two types of high-pressure, single-fluid design systems, and a second dual-fluid (water/nitrogen) nozzle system were evaluated. The in-flight fire scenarios included simulated bulk-loaded fires, containerized fires, flammable liquid fires, and aerosol can explosions. The majority of tests were conducted inside a wide-body DC-10 cargo compartment; additional tests were conducted in a B727 narrow-body compartment. Several tests utilizing one of the high-pressure, single-fluid design systems were conducted according to the Minimum Performance Standard (MPS) for aircraft cargo compartments which standardizes and specifies the fire test performance for halon replacement agents. Parameters such as activation temperature, spray duration, nozzle configuration, and flow rate were varied during the tests to determine the impact on water usage and suppression. The tests determined that the systems were capable of suppressing class-A and class-B cargo fires for extended periods, using varying amounts of water. Water spray systems require additional development and evaluation to become a viable replacement for Halon 1301 because of the weight (agent) penalty associated with the systems tested. Also, the capability of water spray against cargo fires involving aerosol cans needs further investigation.