Part I: Introduction to

Polymer Science
ChE EL 10: Introduction to Polymer Engineering

For classroom use only. Please do not distribute.

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 Course Outline
• Introduction to polymer science - Definition, general terms and
overview

• Polymer synthesis - Types of polymerization reactions;

Mechanisms and kinetics of polymerization; Functional groups
and tactility

• Polymer structure

• Properties of polymeric materials

• Structure-property relationships

• Polymeric material selection

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 Course Outline
• Polymer modification techniques — Polymer
reinforcement; Additives in polymers

• Failure analysis and testing — ASTM techniques

• Design and machining methods — Introduction to

rapid prototyping procedures

• Waste reduction technique — Introduction to life

cycle analysis; Intro to biopolymers and
biodegradation

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 Introduction

• The word polymer is derived from the Greek

poly and meros, meaning many and parts,
respectively.

• A polymer is a large molecule contracted from

many smaller structural units called monomers,
covalently bonded together in any conceivable
pattern.

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• Substances composed of molecules containing
a few up to tens of basic structural units, i.e.,
−CH2− groups in polyethylene, are called
oligomers. Oligomers are a transition between
low-molecular-weight substances and polymers.
A change in the number of basic structural units
in oligomer molecules results in an observable
change of some properties of the substance.

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• The essential requirement for a small molecule to
qualify as a monomer or “building block” is the
possession of two or more bonding sites,
through which each can be linked to other
monomers to form the polymer chain.

• The number of bonding sites is referred to as

functionality.

• Bifunctional monomers form linear

macromolecules.

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• When only one species of monomer is used to
form a macromolecule, the product is called a
homopolymer.

• If the chains are composed of two types of

monomer unit, the material is known as
copolymer.

• If three different monomers are incorporated, a

terpolymer results.

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• Copolymers prepared from bifunctional monomers can be
subdivided further into the following:

1. Statistical copolymers in which the distribution of the

two monomers are at random, but influenced by the
individual monomer reactivities.

2. Alternating copolymers with regular placement along

the chain.

3. Block copolymers comprised of substantial sequences

or blocks of each.

4. Graft copolymers in which blocks of one monomer are

grafted on to a backbone of the other as branches.

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• Plastics are those commercial materials other
than elastomers and fibers that are derived from
synthetic polymers.

• Elastomers are polymers that are capable of

high extension under ambient conditions.

• Other polymers may have characteristics that

enable their fabrication into long fibers suitable
for textile applications.

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 History
• Early humans learned how to process, dye, and weave the
natural proteinaceous fibers of wool and silk and the
carbohydrate fibers of flax and cotton.

• Early South American civilizations such as the Aztecs used

natural rubber (Hevea brasiliensis) for making elastic
articles and for waterproofing fabrics.

• Early humans employed a crude plastic art in tanning the

protein in animal skins to make leather and in heat-formed
tortoise shells. They also used naturally occurring tars as
caulking materials and extracted shellac from the
excrement of small coccid insects (Coccus lacca).

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• In the1830’s, Charles Goodyear developed the
vulcanization process that transformed the sticky latex
of natural rubber into useful elastomer for tire use.

• In 1847, Christian F. Schonbein reacted cellulose with

nitric acid to produce cellulose nitrate. This was used in
the 1860’s as the first man-made thermoplastic, celluloid.

• In 1907, bakelite was developed by the Belgian-

American chemist Leo Baekeland in Yonkers, New York.

• In 1912, General Electric developed glyptal

(unsaturated-polyester resin) as a protective coating
resin.

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• In the 1930’s, DuPont produced a variety of of new
polymers including synthetic rubber and more exotic
materials such as nylon and Teflon.

• By 1938, Dow had produced polystyrene in commercial

scale for the first time.

• In 1939, low density polyethylene was made by

scientists at ICI in eNGLAND.

• Efforts to develop new synthetic polymeric materials,

particularly synthetic rubber were intensified during
WWII when many naturally occurring materials were in
short supply.

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• In the 1950’s, Karl Ziegler and Guilio Natta independently
developed a family of stereospecific transition-metal catalysts that
made possible the commercialization of polypropylene as a major
commodity plastic.

• In the 1960s and 1970s witnessed the development of a number of

high-performance engineering plastics polymers that could
compete favorably with more traditional materials, such as metals,
for automotive and aerospace applications.

These included polycarbonate, poly(phenyl oxide), polysulfones,

polyamides, aromatic polyamides such as Kevlar, and other
high-temperature rigid-chain polymers.

More recently, specialty polymers with electrically conducting,

photo conducting, and liquid-crystalline properties have
appeared for a variety of applications.

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Philippine Resin Consumption

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• Polymers or macromolecules are giant molecules
with molecular weights at least 100 times greater
than those of smaller molecules such as water or
methanol.

• If we disregard metals and inorganic compounds,

we observe that practically everything else in this
world is polymeric. This includes the protein and
nucleic acid in our bodies, the fibers we use for
clothing, the protein and starch we eat, the
elastomers in our automobile tires, and the paint,
plastic wall and floor coverings, foam insulation,
dishes, furniture, pipes, and so forth in our homes.

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• In spite of the many varieties of fibers,
elastomers, and plastic, they all have a similar
structure and are governed by the same
theories. Linear polymers, such as high-density
polyethylene (HDPE), consist of long chains
made up of thousands of covalently bonded
carbon atoms. The repeating unit for HDPE is
represented as [CH CH ] , where n is the number
2 2 n

of repeating units.

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 Classification According to their Origin

Polymers are divided into two basic groups, viz.,

natural polymers and synthetic polymers.

The most important classes of natural polymers are

polysaccharides - basic structural materials of plants,
proteins - fundamental structural materials of animals,
and nucleic acids - carriers of genetic information.

Synthetic polymers are modern materials surrounding

us in everyday life as construction, insulation or
packaging materials, synthetic fibers, coatings, etc.

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 Classification Based on Their Thermal
Processing Behavior

Thermoplastics — polymers that can be heat-

softened in order to process into desired form.
Waste thermoplastics can be recovered and
refabricated by application of heat and pressure.

Example: polyolefins (polyethylene and

polypropylene); PVC or poly(vinyl chloride)

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Thermosets — polymers whose individual chains
have been chemically linked by covalent bonds
during polymerization or by subsequent chemical
or thermal treatment during fabrication.

Examples: Phenolic resins, amino resins,

thermosetting polyester resins, epoxy resins.

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 Classification Based upon the Mechanism of
Polymerization

Addition — Polymerized by sequential addition of

monomers

Example: polyolefins (polyethylene and

polypropylene); PVC or poly(vinyl chloride)

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Condensation — polymers are obtained by the
random reaction of two molecules. A molecule
participating in a polycondensation reaction may
be a monomer, oligomer, or higher-molecular-
weight intermediate each having complementary
functional end units, such as carboxylic acid or
hydroxyl groups. Typically, condensation
polymerizations occur by the liberation of a small
molecule in the form of gas, water, or salt.

Examples: Nylon 6,5; polycarbonate

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Other classification scheme based on
polymerization kinetics:

Chain growth — most addition polymerization

Step growth — most condensation polymerization

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 Classification Based upon Polymer Structure

Homochain polymers — polymers having all

carbon atoms along their backbone

Polyalkylenes — carbon-chain polymers with only

single bonds along the backbone; e.g.
polystyrene, polyolefin, poly(vinyl chloride)

Polyalkenylenes — carbon-chain polymers with

double bonds along the backbone; e.g. diene
elastomers such as polyisprene and polybutadiene

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Heterochain polymers — polymers having other
atoms aside from carbon atoms along their
backbone

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Classification Based upon Molecular Structure

1. Linear chain polymers

2. Branched polymers — contain molecules

having a linear backbone with branches
emanating randomly from it.

3. Network or gel polymers

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 Polymer Nomenclature
Common Names

• Some names are derived from the place of origin

of the material, such as Hevea brasiliensis—
literally “rubber from Brazil”—for natural rubber.

• Other polymers are named after their discoverer,

is is Bakelite, the three-dimensional polymer
produced by condensation of phenol and
formaldehyde, which was commercialized by Leo
Baekeland in 1905.

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• For some important groups of polymers, special
names and systems of nomenclature were
invented. For example, the nylons were named
according to the number of carbons in the
diamine and carboxylic acid reactants
(monomers) used in their syntheses. The nylon
produced by the condensation of 1,6-
hexanediamine (6 carbons) and sebacic acid (10
carbons) is called nylon-6,10.

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 Source Based Names

• Most polymer names used by polymer scientists

are source-based; i.e., they are based on the
common name of the reactant monomer, preceded
by the prefix “poly.” For example, polystyrene is
the most frequently used name for the polymer
derived from the monomer 1-phenylethene, which
has the common name styrene.

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 Source Based Names

• The vast majority of polymers based on the vinyl

group (CH BCHX) or the vinylidene group (CH BCX )
2 2 2

as the repeat unit are known by their source-based

names. For example, polyethylene is derived from
the monomer ethylene, poly(vinyl chloride) from the
monomer vinyl chloride, and poly(methyl
methacrylate) from methyl methacrylate:

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• Many condensation polymers are also named in
this manner. In the case of poly(ethylene
terephthalate), the glycol portion of the name of
the monomer, ethylene glycol, is used in
constructing the polymer name, so that the name
is actually a hybrid of a source based and a
structure-based name.

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• Although it is often suggested that parentheses
be used in naming polymers of more than one
word [like poly(vinylidene chloride)] but not for
single-word polymers (like polyethylene), many
authors omit entirely the use of parentheses for
either case (like polyvinylidene chloride). Thus
there exists a variety of practices with respect to
even source-based names.

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• Copolymers are composed of two or more monomer
units. Source-based names are conveniently used to
describe copolymers by using an appropriate term
between the names of the monomers. Any of a half
dozen or so connecting terms may be used,
depending on what is known about the structure of
the copolymer. When no information is specified
about the sequence of monomer units in the
copolymer, the connective term co is used in the
general format poly(A-co-B), where A and B are the
names of the two monomers. An unspecified
copolymer of styrene and methyl methacrylate would
be called poly[styrene-co-(methyl methacrylate)].

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 Structure-Based Names

• Although source-based names are generally

employed for simple polymers, the international
body responsible for systematic nomenclature of
chemicals, IUPAC, has published a number of
reports for the naming of polymers, now being
accepted for more complex polymers.

• The IUPAC system names the components of

the repeat unit, arranged in a prescribed order.

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• However, once the order is selected, the naming
is straightforward for simple linear molecules, as
indicated in the following examples:

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 Linkage-Based Names

• Many polymer “families” are referred to by the

name of the particular linkage that connects the
polymers (Table 2). The family name is “poly”
followed by the linkage name. Thus, those
polymers that contain the carbonate linkage are
known as polycarbonates; those containing the
ether linkage are called polyethers, etc.

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 Trade Names, Brand Names and Abbreviations

• Trade (and/or brand) names and abbreviations are often

used to describe materials. They may be used to identify
the product of a manufacturer, processor or fabricator and
may be associated with a particular product or with a
material or modified material.

• Trade names are used to describe specific groups of

materials that are produced by a specific company or
under licence of that company.

• Bakelite is the trade name given for the

phenolformaldehyde condensation polymer developed by
Baekeland.

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 Trade Names, Brand Names and Abbreviations

• A sweater whose contents are described as

containing Orlon contains polyacrylonitrile fibers
that are “protected” under the Orlon trademark
and produced or licenced to be produced by the
holder of the Orlon trademark.

• Also, Carina, Cobex, Dacovin, Darvic, Elvic, Geon,

Koroseal, Marvinol, Mipolam, Opalon, Plioflex,
Rucon, Solvic, Trulon, Velon, Vinoflex, Vygen, and
Vyram are all trade names for poly(vinyl chlorides)
manufactured by different companies.

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Trade Names, Brand Names and Abbreviations

• Some polymers are better known by their trade

name than their generic name. For instance,
polytetrafluoroethylene is better known as Teflon,
the trade name held by DuPont. An extensive
listing of trade names is given in Appendix B of
this text. Abbreviations, generally initials in
capital letters, are also employed to describe
materials. Table 4 contains a listing of some of
the more widely employed abbreviations and the
polymer associated with the abbreviation.

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