FIGURE 3.1 U.S. production of thermoplastics by type, 1990. SOURCE: Reprinted with permission from Chemical & Engineering News (1991), p. 54. Copyright© 1991 by the American Chemical Society.

packaging applications), with current sales nearly one-quarter of those for polypropylene. For the long term, the majority of commodity thermoplastics are expected to follow their traditional growth (Chemical & Engineering News, 1992), with continued opportunities for both process and product innovation. Future activities will focus strongly on recycling. In the case of PET, recycling can be accomplished by chemical depolymerization to monomers or oligomers followed by repolymerization to PET or other products. Such processes are currently in use for products that come into contact with food, while simple reprocessing is used for less critical products.

The so-called engineering thermoplastics, which include the higher-performance, more expensive polymers such as the polyacetals, polycarbonates, nylons, polyesters, polysulfones, polyetherimides, some acrylonitrile butadiene styrene (ABS) materials, and so on, have generally exhibited stronger growth than the commodity plastics (see Table 3.2). These materials generally have greater heat resistance and better mechanical properties than the less expensive commodity thermoplastics and, therefore, are used in more demanding applications, such as aircraft, automobiles, and appliances. A major area of development is

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