Page 15 - Handbook of Plastics Technologies

Source: Handbook of Plastics Technologies

CHAPTER 1

INTRODUCTION TO

POLYMERS AND PLASTICS

Carol M. F. Barry, Anne-Marie Baker, Joey L. Mead
University of Massachusetts
Lowell, Massachusetts

1.1 INTRODUCTION

Plastics are an important part of everyday life; products made from plastics range from so-
phisticated products, such as prosthetic hip and knee joints, to disposable food utensils.
One of the reasons for the great popularity of plastics in a wide variety of industrial appli-
cations is the tremendous range of properties exhibited by plastics and their ease of pro-
cessing. Plastic properties can be tailored to meet specific needs by varying the atomic
composition of the repeat structure, by varying molecular weight and molecular weight
distribution. The flexibility can also be varied through the presence of side chain branch-
ing, via the lengths and polarities of the side chains. The degree of crystallinity can be con-
trolled through the amount of orientation imparted to the plastic during processing,
through copolymerization, blending with other plastics, and through the incorporation of
an enormous range of additives (fillers, fibers, plasticizers, stabilizers). Given all of the av-
enues available for tailoring any given polymer, it is not surprising that the variety of
choices available to us today exist.
Polymeric materials have been used since early times even though their exact nature
was unknown. In the 1400s, Christopher Columbus found natives of Haiti playing with
balls made from material obtained from a tree. This was natural rubber, which became an
important product after Charles Goodyear discovered that the addition of sulfur dramati-
cally improved the properties; however, the use of polymeric materials was still limited to
natural-based materials. The first true synthetic polymers were prepared in the early 1900s
using phenol and formaldehyde to form resins—Baekeland’s Bakelite. Even with the de-
velopment of synthetic polymers, scientists were still unaware of the true nature of the ma-
terials they had prepared. For many years, scientists believed they were colloids—a
substance that is an aggregate of molecules. It was not until the 1920s that Herman
Staudinger showed that polymers were giant molecules or macromolecules. In 1928,
Carothers developed linear polyesters and then polyamides, now known as nylon. In the
1950s, Ziegler and Natta’s work on anionic coordination catalysts led to the development
of polypropylene, high-density, linear polyethylene, and other stereospecific polymers.
More recent developments include Metallocene catalysts for preparation of stereospecific
polymers and the use of polymers in nanotechnology applications.

1.1
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