Tecnología De Los Plásticos

Páginas: 331 (82720 palabras) Publicado: 23 de octubre de 2012
4
Industrial Polymers
4.1

Introduction

The first completely synthetic plastic, phenol-formaldehyde, was introduced by L. H. Baekeland in 1909,
nearly four decades after J. W. Hyatt had developed a semisynthetic plastic—cellulose nitrate. Both Hyatt
and Baekeland invented their plastics by trial and error. Thus the step from the idea of macromolecules to
the reality of producing them atwill was still not made. It had to wait till the pioneering work of
Hermann Staudinger, who, in 1924, proposed linear molecular structures for polystyrene and natural
rubber. His work brought recognition to the fact that the macromolecules really are linear polymers.
After this it did not take long for other materials to arrive. In 1927 poly(vinyl chloride) (PVC) and
cellulose acetate weredeveloped, and 1929 saw the introduction of urea-formaldehyde (UF) resins.
The production of nylon-6,6 (first synthesized by W. H. Carothers in 1935) was started by Du Pont in
1938, and the production of nylon-6 (perlon) by I. G. Farben began in 1938, using the caprolactam
route to nylon developed by P. Schlock. The latter was the first example of ring-opening polymerization.
The years prior toWorld War II saw the rapid commercial development of many important plastics, such
as acrylics and poly(vinyl acetate) in 1936, polystyrene in 1938, melamine–formaldehyde (formica) in
1939, and polyethylene and polyester in 1941. The amazing scope of wartime applications accelerated
the development and growth of polymers to meet the diverse needs of special materials in different fields
ofactivity.
The development of new polymeric materials proceeded at an even faster pace after the war. Epoxies
were developed in 1947, and acrylonitrile–butadiene–styrene (ABS) terpolymer in 1948. The polyurethanes, introduced in Germany in 1937, saw rapid development in the United States as the technology
became available after the war. The discovery of Ziegler–Natta catalysts in the 1950s broughtabout the
development of linear polyethylene and stereoregular polypropylene. These years also saw the emergence
of acetal, polyethylene terephthalate, polycarbonate, and a host of new copolymers. The next two decades
saw the commercial development of a number of highly temperature-resistant materials, which included
poly(phenylene oxide) (PPO), polysulfones, polyimides, polyamide-imides, andpolybenzimidazoles.
Numerous plastics and fibers are produced from synthetic polymers: containers from polypropylene,
coating materials from PVC, packaging film from polyethylene, experimental apparatus from Teflon,
organic glasses from poly(methyl methacrylate), stockings from nylon fiber—there are simply too many
to mention them all. The reason why plastics materials are popular is that they mayoffer such advantages
as transparency, self-lubrication, lightweight, flexibility, economy in fabricating, and decorating.
Properties of plastics can be modified through the use of fillers, reinforcing agents, and chemical
additives. Plastics have thus found many engineering applications, such as mechanical units under stress,
low-friction components, heat- and chemical-resistant units, electricalparts, high-light-transmission
applications, housing, building construction functions, and many others. Although it is true that in these
applications plastics have been used in a proper manner according to our needs, other ways of utilizing
both natural and synthetic polymers may still remain. To investigate these further possibilities, active

4-1
q 2006 by Taylor & Francis Group, LLC 4-2

Plastics Technology Handbook

research has been initiated in a field called specialty polymers. This field relates to synthesis of new
polymers with high additional value and specific functions.
Many of the synthetic plastic materials have found established uses in a number of important areas of
engineering involving mechanical, electrical, telecommunication, aerospace, chemical,...
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