The most basic component of plastic and elastomer materials is polymer. The word polymer is derived from the Greek term for “many parts.” Polymers… [620683]

1 Introduction to Plastics
and Polymers
The most basic component of plastic and
elastomer materials is polymer. The word polymer is
derived from the Greek term for “many parts.”
Polymers are large molecules comprised of many
repeat units, called monomers that have been
chemically bonded into long chains. Since World
War II, the chemical industry has developed a large
quantity of synthetic polymers to satisfy the mate-
rials needs for a diverse range of products, includingpaints, coatings, fibers, films, elastomers, and struc-
tural plastics. Literally thousands of materials can be
called “plastics,” although the term today is typically
reserved for polymeric materials, excluding fibers,
which can be molded or formed into solid or semi-
solid objects. As of the beginning of 2012, IDES
The Plastics Web
/C210(http://www.ides.com ) listed
over 85,000 different grades of plastic from over800 suppliers.
This book will narrow the plastics field down to
plastic films and flexible sheet materials. Generallyfilms are used as barriers, they keep liquid or gases
on one side of the film. Barrier film applications
include packaging, coating, and gloves. There are
other applications of polymer films, such as
membranes, but that application is not discussed in
this book. Users of films for packaging are usually
interested in what goes through, that is permeation
properties, and how tough or strong the films are,
how easy are they to tear and puncture.
The first four chapters of this book are introduc-
tory in nature. The first chapter is a review of poly-mer chemistry and plastic formulation. The second
chapter is a lengthy chapter on films properties. First
discussed are the physical properties of films, such as
specific gravity, dimensional stability and coefficient
of friction. Second are the mechanical properties
such as tensile strength, elongation, modulus, tear
resistance, and folding endurance. Third are thermal
properties such as melting point, glass transition
temperature and melt index which affect use,production and processing of films. Fourth are
permeation properties which are related to the
passage of liquids, vapors or gases, plastic or poly-
meric materials. The third chapter is on production
methods to make and modify plastic film. The fourth
chapter covers some of the commercial uses of films.
The chapters that follow are the data chapters.
Each chapter covers plastics that fall into particular
types based on the chemistry of the polymer. Each ofthese chapters reviews the chemical structures then
presents data in tabular and graphical form.
The subject of this chapter includes polymeriza-
tion chemistry and the different types of polymers
and how they can differ from each other. Since
plastics are rarely “neat”, reinforcement, fillers and
additives are reviewed. A basic understanding of
plastic and polymer chemistry will make the
discussion of properties of specific films easier to
understand and it also provides a basis for the intro-
ductions of the plastic families in later chapters. Thissection is taken from The Effect of Temperature and
Other Factors on Plastics
1andPermeability Prop-
erties of Plastics and Elastomers ,2but it has been
rewritten, expanded and refocused on polymer films.
1.1 Polymerization
Polymerization is the process of chemically
bonding monomer building blocks to form large
molecules. Commercial polymer molecules are
usually thousands of repeat units long. Polymeriza-
tion can proceed by one of several methods. The two
most common methods are called addition andcondensation polymerization.
1.1.1 Addition Polymerization
In addition polymerization (sometimes called
chain-growth polymerization), a chain reaction adds
Film Properties of Plastics and Elastomers. DOI: 10.1016/B978-1-4557-2551-9.00001-3
Copyright /C2112012 Elsevier Inc. All rights reserved. 1