ME6403 -EMM - Polymer types and polymer synthesis

1. Mr.S.Gokul/Assistant Professor/Department of Mechanical Engineering/Sri Eshwar College of Engineering
POLYMER TYPES AND POLYMER SYNTHESIS &
PROCESSING
 Polymers are classified in several ways – by how the
molecules are synthesized, by their molecular structure,
or by their chemical family.
 For example, linear polymers consist of long molecular
chains, while the branched polymers consist of primary
long chains and secondary chains that stem from these
main chains. However, linear does not mean straight
lines.
 The better way to classify polymers is according to their
mechanical and thermal behavior. Industrially polymers
are classified into two main classes – plastics and
elastomers.
 Plastics are moldable organic resins. These are either
natural or synthetic, and are processed by forming or
molding into shapes.
 Plastics are again classified in two groups depending on
their mechanical and thermal behavior as thermoplasts
(thermoplastic polymers) and thermosets
(thermosetting polymers).
Thermoplasts: These plastics soften when heated and
harden when cooled – processes that are totally reversible
and may be repeated. These materials are normally
fabricated by the simultaneous application of heat and
pressure.
 They are linear polymers without any cross-linking in
structure where long molecular chains are bonded to
each other by secondary bonds and/or inter-wined.
 Common thermoplasts are: acrylics, PVC, nylons,
polypropylene, polystyrene, polymethyl methacrylate
(plastic lenses or perspex), etc.
 Thermoplastic polymers consist of a very long chain of
carbon atoms covalently bonded together.
Thermosets: These plastics require heat and pressure to
mold them into shape.
 They are formed into a permanent shape and cured or
‘set’ by chemical reactions such as extensive cross-
linking.
 They cannot be re-melted or reformed into another
shape but decompose upon being heated to too high a
temperature.
 Thus thermosets cannot be recycled, whereas
thermoplasts can be recycled. The term thermoset
implies that heat is required to permanently set the
plastic.
 Epoxies, vulcanized rubbers, phenolics, unsaturated
polyester resins, and amino resins (ureas and
melamines) are examples of thermosets.
Elastomers: Also known as rubbers, these are polymers
which can undergo large elongations under load, at room
temperature, and return to their original shape when the
load is released. There are number of man-made
elastomers in addition to natural rubber.
Addition polymerization: also known as chain reaction
polymerization is a process in which multi-functional
monomer units are attached one at a time in chain like
fashion to form linear/3-D macro-molecules.
 To initiate the process, an initiator is added to the
monomer. Polyethylene, polypropylene, PVC, and

2. Mr.S.Gokul/Assistant Professor/Department of Mechanical Engineering/Sri Eshwar College of Engineering
polystyrene are synthesized using addition
polymerization.
Condensation polymerization: also known as step growth
polymerization, involves more than one monomer species;
and there is usually a small molecular weight by-product
such as water, which is eliminated.
The by-product, methyl alcohol, is condensed off and the
two monomers combine to produce a larger molecule
(meter repeat unit).
Polyamide (PA)
Polyamides are very well known by their trade name 'nylons'
which is one of the first engineering plastics. Nylons melt
processable thermoplastics whose main structure contains a
repeating amide group (CO.NH).
Characteristics: Good mechanical strength, abrasion
resistance, and toughness; low coefficient of friction; absorbs
water and some other liquids.
Application: Bearings, gears, cams, bushings, handles, and
jacketing for wires and cables Rope, extruded hose, soles for
footwear, automobile speedometers and wiper gears. Electrical
applications include connectors, plugs, wire insulation, antenna
mounts and terminals.
Acrylonitrile-butadiene-styrene (ABS):
Polystyrene is a tertiary polymer having three monomers-
Acrylonitrile, Butadiene and Styrene.
Characteristics: Outstanding strength and toughness,
resistance to heat distortion; good electrical properties;
flammable and soluble in some organic solvents.
Application: Refrigerator lining, lawn and garden
equipment, toys, highway safety devices. telephone receivers,
helmets, computer housings, refrigerator door liners, electro-
magnetic interference- radio frequency shielding.

3. Mr.S.Gokul/Assistant Professor/Department of Mechanical Engineering/Sri Eshwar College of Engineering
Polyethylene terephthalate (PET )
Polyethylene terephthalate is important thermoplastic
polyester. Because of its properties and relatively low cost, its
application is continuously expanding.
Characteristics: One of the toughest of plastic films; excellent
fatigue and tear strength, and resistance to humidity acids,
greases, oils and solvents
Application: Magnetic recording tapes, clothing, automotive
tire cords, beverage containers, films for photography and
packaging, beverage bottles, auto parts, gears, cams, and water
meter chambers.
Polycarbonates (PC)
Characteristics: Dimensionally stable: low water absorption;
transparent; very good impact resistance and ductility.
Application: Safety helmets, lenses light globes, base for
photographic film
Polyimide (PI)
Polyimides are made by reacting aromatic diamines and
dianhydrides.
The most important property of the polymer is the resistance to
high temperature.
The drawbacks of these polymers are its poor stability in
sunlight and poor resistance to oxidizing acids.
The higher cost of this family of polymers is often justified by
their functional advantages.
Applications
(i) Films are used for circuit board types of applications where
operating temperatures are high.
(ii) In resin form, they are used as adhesives.
(iii) Graphite or PTFE added grades are used as self-lubricated
bearings because of their tribological properties.
(iv) Composite with polyimide matrix are used in space shuttle
applications.
Polyamide-imides (PAI)
Polyamide-imides are high temperature, high strength
polymers. They are formed by a condensation reaction between
trimetallic anhydrides and various diamines.
These polymers have a chemical structure, which has the
combination of nitrogen bond of a polyamide and the ring
structure of polyimide.
These polymers have high strength and high maximum
operating temperature
The impact strength is high
PAI is costly polymer.

4. Mr.S.Gokul/Assistant Professor/Department of Mechanical Engineering/Sri Eshwar College of Engineering
Applications
(i) Valves made from PAl are used in hot water systems.
(ii) PAI is are used in the under hood plastic parts of
automobiles and high temperature electrical applications.
Polyphenylene oxide (PPO)
The repeating benzene rings hinder the rotation polymer
molecules and this gives the polymer PPO high .rigidity, high
strength .and heat deflection temperatures.
It has good electrical properties.
High impact strength and low water absorption rate.
The main drawback is that it has poor processing
characteristics
Applications
Typical applications of PPO are computer housing, TV tuners,
electrical connectors, automobile dashboards, and exterior
body parts.
Polyether ether ketone (PEEK)
These polymers are costly and are used in high performance
applications where the cost can be justified by the properties.
The structure is of R-O-R type having benzene rings linked
with an oxygen bond. They are high temperature polymers
and they can be in continuous use at temperatures as high as
315°C.
They have good dimensional stability even at elevated
temperatures and low flammability.
They are very resistant to many chemicals, hot water and low
pressure steam.
Similar to PPS, the various grades of PEEK are unfilled, glass
filled and carbon fibre filled.
Applications
(i) PEEKs are used as high temperature electrical insulations
and coatings.
(ii) Composites with PEEK matrix are used in aircrafts and
aerospace applications.
Polyphenylene Sulphide (PPS)
PPS is made by reacting dichlorobenzene with sodium
sulphide.
PPS has excellent chemical resistance.
Its resistance to moisture absorption is exceptional while it is
not resistant to U- V radiation from sunlight.
Applications
(i)Industrial applications of PPS are chemical processing
equipments such as submersible, centrifugal, vane and
gear type pumps.
(ii) PPS compounds are suitable for many automobile
applications such as emission control systems because
of their resistance to corrosion effects due to engine
exhaust gases.
(iii) Corrosion resistant and thermally stable coatings of
PPS are used for oil field pipes, valve fittings,
couplings etc.

5. Mr.S.Gokul/Assistant Professor/Department of Mechanical Engineering/Sri Eshwar College of Engineering
Urea Formaldehyde
Urea reacts with formaldehyde by condensation
polymerisation reaction, which produces water as a by-
product.
The amine groups (-NH2) at the end of the molecule
react with more formaldehyde molecules ·to produce
a highly rigid network polymer structure. Like
phenolics, urea and formaldehyde are first partially
polymerised to produce a low molecular weight
prepolymer. This is ground into a powder and
compounded with fillers. This moulding compound
can then be compression moulded.
Structure and Properties
The high reactivity of urea formaldehyde prepolymers enable
the making of highly cross-linked thermoset products. When
these resins are combined with fillers the obtained products
have good strength, rigidity and impact resistance. –
Applications
Cellulose filled moulding compounds are used in.
electrical wall plates, switches, circuit breakers, knobs
and handles.
Urea water-soluble resins find application as adhesives
in wood particle board, plywood, boat hulls and
furniture assemblies.
Phenolics (Phenol formaldehyde)
Phenolic thermosets are the first major polymer materials used
by industry. commercial phenol formaldehyde polymers were
produced, under the trade name 'Bakelite'. Phenolic resins are
most commonly produced by the condensation polymerization
of phenol with formaldehyde Phenolic resins are partly
polymerized to form a brittle solid.
The highly cross-linked aromatic structure of this polymer
produces high hardness, rigidity and strength combined with
good heat and electrical insulating properties. These polymers
are easily mouldable and are filled with various filler elements
to obtain the desired properties.
Applications
Phenolic moulding compounds are widely used in electrical
parts such as switches, distributor caps, wiring devices,
connectors and telephone relay systems.
They are used in power-assist brake components and
transmission parts in automobiles.
They are moulded into standard shapes and are subsequently
machined as gears, cams and other mechanical components.
They are used for handles and knobs for small appliances.
Phenolic resins are used as moisture resistant adhesives in
laminate plywood.
Phenolic resins are also used as binder material for sand in
the shell moulding process and for abrasive grains in
grinding wheels.

6. [Faculty]
ME6403– EMM – CIA III QB
6 / 1
Some Common Addition Polymers
Name(s) Formula Monomer Properties Uses
Polyethylen
e
low density
(LDPE)
–(CH2-CH2)n–
ethylene
CH2=CH2
 soft, waxy solid
 It is whitish in colour
and often fabricated
into clear thin films.
 By adding colourants, a
wide variety of coloured
products
are also obtained.
 film wrap,
 plastic bags,
 packing
film,
 wire
insulation,
 paper
coatings etc.
Polyethylen
e
high density
(HDPE)
–(CH2-CH2)n–
ethylene
CH2=CH2
 rigid, transparent solid
 electrical
insulation,
 bottles,
 toys,
 undergroun
d piping,
 household
items
Polypropyl
ene
(PP)
different
grades
–[CH2-
CH(CH3)]n–
propylene
CH2=CHCH3
 atactic: soft, elastic
solid
 isotactic: hard, strong
solid
 house
wares,
 packaging,
 tanks and
battery
cases.
 carpet
fibres,
 ropes and
bags
 over wrap
films for soft
goods.
Poly(vinyl
chloride)
(PVC)
–(CH2-
CHCl)n–
vinyl chloride
CH2=CHCl
 strong rigid ,solid,
 good electrical
properties and high
solvent resistance
 pipes,
flooring,
furniture
 electrical
insulation,
 flexible
garden
hoses,
 gaskets,
seals and
 insulation
tapes.
 corrosion-
resistant
coatings

7. [Faculty]
ME6403– EMM – CIA III QB
7 / 1
Polystyrene
(PS)
–[CH2-
CH(C6H5)]n–
styrene
CH2=CHC6H5
 hard, rigid, clear solid
 soluble in organic
solvents
 toys,
cabinets
packaging
(foamed)
 disposable
food
 containers,
trays,
 made into
rigid
 foams and
used for
thermal
Insulation,
radio/TV
components
.
Poly tetra
fluoro
ethylene
(PTFE,
Teflon)
–(CF2-CF2)n–
tetrafluoroethyl
ene
CF2=CF2
 resistant, smooth solid
Non-stick surfaces,
electrical
insulation ,
chemically
resistant pipe
pump parts and
vessels.
slide way inserts in
CNC machines,
non-lubricated
bearings due to its
low coefficient of
friction.
High temperature
cable insulations,
insulation tapes,
moulded electrical
components, non-
stick
coatings for
cooking utensils
Poly(methy
l
methacryla
te)
(PMMA,
Lucite,
Plexiglas)
–[CH2-
C(CH3)CO2CH
3]n–
methyl
methacrylate
CH2=C(CH3)CO2
CH3
 hard, transparent solid
lighting covers,
signs
skylights, lenses in
cameras,
flashlights, safety
glasses, window
glass, weather
proof coatings