This paper reviews the fire hazard properties of some transformer fluids of reduced flammability. Fluids examined include a silicone (polydimethylsiloxane), a high molecular weight aliphatic hydrocarbon, and a polyalphaolefin. Fire hazard properties considered include ease of ignition, flame spread, fire growth and rate of heat release (large scale pool burns), rate of smoke evolution, fire gas and smoke toxicity, and extinguishment behavior.
Aircraft seat materials were evaluated in terms of their thermal performance. The materials were evaluated using (a) thermogravimetric analysis, (b) differential scanning calorimetry, (c) a modified NBS smoke chamber to determine the rate of mass loss and (d) the NASA T-3 apparatus to determine the thermal efficiency. In this paper, the modified NBS smoke chamber will be described in detail since it provided the most conclusive results. The NBS smoke chamber was modified to measure the weight loss of materials when exposed to a radiant heat source over the range of 2.5 to 7.5 W/cm sq. This chamber has been utilized to evaluate the thermal performance of various heat blocking layers utilized to protect the polyurethane cushioning foam used in aircraft seats. Various kinds of heat blocking layers were evaluated by monitoring the weight loss of miniature seat cushions when exposed to the radiant heat. The effectiveness of aluminized heat blocking systems was demonstrated when compared to conventional heat blocking layers such as neoprene. All heat blocking systems showed good fire protection capabilities when compared to the state-of-the-art, i.e., wool-nylon over polyurethane foam.
The focal point of this work is a full-scale, wide-body test article, constructed from a surplus C-133 aircraft. This paper describes the following major elements of the development and application of the C-133 article to study postcrash cabin fires: (1) initial development, capabilities and instrumentation; (2) derivation of fuel fire test conditions based on physical modeling and large-scale fire tests; (3) characterization of cabin fire hazards arising solely from an external fuel fire without the contribution of interior materials; (4) characterization of cabin fire hazards resulting from the exposure of wide-body interior materials to an external fuel fire (the fuel fire, by itself, would be clearly survivable over the test duration if the interior were noncombustible); and (5) evaluation of the effectiveness of urethane seat cushion fire blocking layers and improved cushioning materials over a range of test configurations. The results of the extensive tests that have been performed to date, especially over the past 12 to 18 months, are beginning to improve our understanding of the cabin hazards and important parameters associated with postcrash fire, and, by the example of seat cushions, illustrate how safety benefits can be realized by the useage of improved materials.
Measurements were conducted on 7.6 x 7.6 cm samples of polyurethane seat cushion material in a modified National Bureau of Standards smoke density chamber to simulate real life conditions for an onboard aircraft fire or post-crash fire. In this study, a non-flaming heat radiation condition was simulated. Two aluminized polymeric fabrics (Norfab 11HT-26-A and Preox 1100-4) and one neoprene type material in two thicknesses (Vonar 2 and 3) were tested as heat blocking layers to protect the urethane foam from rapid heat degradation. Thermogravimetric analysis and differential scanning calorimetry were performed to characterize thermally the materials tested. It was found that Vonar 2 or 3 provided approximately equal thermal protection to F.R. urethane as the aluminized fabrics, but at a significant weight penalty. The efficiency of the foams to absorb heat per unit mass loss when protected with the heat blocking layer decreases in the heating range of 2.5-5.0 W/sq cm, but remains unchanged or slightly increases in the range of 5.0-7.5 W/sq cm. The results show that at all heat flux ranges tested the usage of a heat blocking layer in aircraft seats significantly improves their thermal performance.
This paper presents results of an investigation aimed at obtaining soot reduction by suppressing solid fuel gasification rate under fire conditions. Tests were conducted with polyethylene diffusion flames and various techniques were used to alter the heat balance on the fuel surface, thereby changing the fuel gasification rate. The resulting soot production rates were measured and analysis of the data shows that fire retardant additives whose presence in the fuel decreases its gasification rate are also effective soot suppressants. In particular, alumina trihydrate which also liberates water into the pyrolysis region was found to be an effective soot suppressant.
