an integral part of our society, serving sophisticated functions that improve the quality of our life.

The unique and valuable properties of polymers have their origins in the molecular composition of their long chains and in the processing that is performed in producing products. Both composition (including chemical makeup, molecular size, branching and cross-linking) and processing (affected by flow and orientation) are critical to the estimated properties of the final product. This chapter considers the various classes of polymeric materials and the technical factors that contribute to their usefulness. In spite of the impressive advances that have been made in recent years, there are still opportunities for further progress, and failure to participate in this development will consign the United States to second-class status as a nation.

MATERIALS

Structural Polymers

The familiar categories of materials called plastics, fibers, rubbers, and adhesives consist of a diverse array of synthetic and natural polymers. It is useful to consider these types of materials together under the general rubric of structural polymers because macroscopic mechanical behavior is at least a part of their function. Compared with classical structural materials like metals, the present usage represents a considerable broadening of the term. As shown in Table 3.1, man-made plastics, fibers, and rubber accounted for U.S. production of about 71 billion pounds in 1992 (Chemical & Engineering News, 1993), and production has tripled over the last 20 years. The price received by the original manufacturer ranges from roughly $0.50 to several dollars per pound, depending on the material. At $20 per barrel, crude oil costs about $0.06 per pound, and so conversion to polymers represents considerable value added. Because these materials go through several manufacturing steps before reaching the final consumer, the ultimate impact on the national economy is measured in the hundreds of billions of dollars each year.

TABLE 3.1 U.S. Production of Some Man-Made Structural Polymers, 1992

 

Pounds (billions)

Plastics

57.6

Fibers

9.1

Rubber

4.2

 

SOURCE: Data from Chemical & Engineering News (1993), p. 44.



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