Chemistry Reference
In-Depth Information
CHAPTER
1
Introductory Concepts
and Definitions
Knowledge is a treasure, but practice is the key to it.
—Thomas Fuller, Gnomologia
1.1
Some Definitions
Some basic concepts and definitions of terms used in the polymer literature are
reviewed in this chapter. Much of the terminology in current use in polymer sci-
ence has technological origins, and some meanings may therefore be understood
by convention as well as by definition. Some of these terms are included in this
chapter since a full appreciation of the behavior and potential of polymeric mate-
rials requires acquaintance with technical developments as well as with the more
academic fundamentals of the field. An aim of this topic is to provide the reader
with the basic understanding and vocabulary for further independent study in both
areas.
Polymer technology is quite old compared to polymer science. For example,
natural rubber was first masticated to render it suitable for dissolution or spread-
ing on cloth in 1820, and the first patents on vulcanization appeared some twenty
years later. About another one hundred years were to elapse, however, before it
was generally accepted that natural rubber and other polymers are composed of
giant covalently bonded molecules that differ from “ordinary” molecules primar-
ily only in size. (The historical development of modern ideas of polymer constitu-
tion is traced by Flory in his classical topic on polymer chemistry
[1]
, while
Brydson
[2]
reviews the history of polymer technology.) Since some of the terms
we are going to review derive from technology, they are less precisely defined
than those the reader may have learned in other branches of science. This should
not be cause for alarm, since all the more important definitions that follow are
clear in the contexts in which they are normally used.
1.1.1
Polymer
Polymer means “many parts” and designates a large molecule made up of smaller
repeating units. Thus the structure of polystyrene can be written
