of polymers and polymer composites as well as high-strength steel alloys, and much of the credit for improved fuel efficiency can be traced to the introduction of these advanced materials. Present-generation automobiles are about 10 percent polymer by weight, and the potential for further substitution is substantial.

The potential is greater yet for aircraft. For each pound saved in the weight of the airframe, the payload can be increased by a pound, and over the life of the aircraft the payback is large. Polymeric materials have made important inroads in general aviation. The airframe of the Beech Starship, for example, is almost entirely polymer and polymer composite, demonstrating the viability of polymers for all nonengine aircraft parts. Less progress has been made in commercial and military aircraft, which follow more conservative design philosophies. But the potential is evident, and extensive substitution can be predicted with confidence.

Further progress in substituting polymers in the transportation area will be based on the high strength and durability of polymers and polymer composites. Further progress in manufacturing processes, repair procedures, and failure mode control will enhance the use of polymers. There is no fundamental reason that polymeric materials cannot be introduced in all areas other than those that expose the materials to very high temperatures, such as engine parts and some aircraft surfaces. One of the best-established uses of polymers is the use of polymeric elastomers in tires, a critical application that affects safety.

Polymers are widely used in the form of foamed insulation, especially in buildings and refrigerators. Although there are concerns about fire and smoke hazards, this use will probably increase. The use of chlorofluorocarbons (CFCs) as blowing agents and foam cell fillers has largely been phased out to reduce ozone layer depletion. Polymers are also used as components in other energy devices and equipment, such as solar systems, fuel cells, batteries, and even reactors. Applications of polymers are discussed in the vignettes "Polymers in Lubricants" and "Polymers for Oil Recovery."

Polymer science and engineering will continue to have a significant impact on energy conservation and on transportation. There is further need for development of better materials having unique properties for applications in these areas. Many will be high-value-added applications, thereby justifying a significant research effort and the use of more expensive materials.

NATIONAL DEFENSE

The military uses polymers widely in diverse applications. These include clothing such as bulletproof vests and helmets, now made exclusively of such polymers as Kevlar® and Spectra®. Structures such as tents, huts, and bridges are made of polymers, as are aircraft, ground vehicles, and naval structures.

As in civilian aircraft, the use of polymers in military aircraft would reduce their weight, thereby conferring the key competitive advantage of longer range and increased payload (for armaments, ammunition, and electronic equipment).



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