Steel and Plastic

Plastics' behavior in fire depends upon the nature and scale of the fire as well as the surrounding conditions and how the products are designed. For example, the virtually all-plastic 35 mm slide projectors use a very hot electric bulb. When designed with a metal heat reflector with an air-circulating fan next to its very high heat dissipating light, the all-plastic projector operates with no fire hazard.

Steel structural beams cannot take the heat of a fire operadng at and above 1500°F (816°C); they just loose all their strength, modulus of elasticity, etc.(Fig. 6.7). The unfortunate disaster of the Twin Towers in New York City on September 11, 2001; fires after being hit by planes is an example. As reviewed to protect steel from this environment they can obtain a temporary short dme protecdon by being covered with products such as concrete and certain plasties. To significandy extend the life of structural beams hard wood (thicker, etc.) can be used; thus people can escape even though the wood slowly burns. The more useful and reliable structural beams would be using reinforced plastics (RPs) that meet structural performance requirements with a much more extended supporting life than wood. To date these RPs are not used in this type of fire environment because their costs are very high.

When plastics are used, their behavior in a fire situation must be understood. Ease of ignition, the rate of flame spread and of heat release, smoke release, toxicity of products of combustion, and other factors must be taken into account. A plastic's behavior in fire depends upon the nature and scale of the fire as well as the surrounding conditions. Fire is a highly complex, variable phenomenon, and the behavior of plastics in a fire is equally complex and variable. Fire tests of plastics, like fire tests generally, are frequendy highly specific, with the results being specific to the tests. The results of one type of test do not

Strength vs. temperature of steel and plastics (Courtesy of Plastics FALLO)

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